Science units Grade 12 advanced
Contents
12AB.1 Biological energetics 391 12AC.1 The periodic table 455 12AP.1 Gravity and circular motion 507
12AB.2 Transport systems 401 12AC.2 Rates of reaction 465 12AP.2 The nature of matter 515
12AB.3 Control, coordination and 413 12AC.3 Acids and K values 471 12AP.3 Thermodynamics 525 homeostasis
12AB.4 Human immune system 427 12AC.4 Energy and entropy 477 12AP.4 Oscillations 533
12AB.5 Genetic inheritance 435 12AC.5 Organic reaction 483 12AP.5 Electrostatic charge and 543 mechanisms force
12AB.6 Ecological relationships 441 12AC.6 Aromatic organic chemistry 489 12AP.6 Quantum and nuclear 557 physics
12AB.7 Biotechnology 449 12AC.7 Making and using chemicals 495 12AP.7 Astrophysics and cosmology 569
12AC.8 Macromolecules 501
Science scheme of work: Grade 12 advanced units 270 hours
1st semester 124 teaching hours
Biology: 48 hours Chemistry: 37 hours Physics: 39 hours
Unit 12AB.0: Revision unit Unit 12AC.0: Revision unit Unit 12AP.0: Revision unit Revision of key ideas from Grade 11. Revision of key ideas from Grade 11. Revision of key ideas from Grade 11. 3 hours 3 hours 3 hours
Unit 12AP.1: Gravity and circular motion Unit 12AB.1: Biological energetics Unit 12AC.1: The periodic table Centripetal acceleration and force. Angular velocity. Biochemistry of anaerobic and aerobic respiration. Periodicity in ionisation energy, electron affinity and Gravitational field strength. Newton's law of ATP structure and generation. Biochemistry of electronegativity. Properties, compounds and trends gravitation. Satellites in circular orbit. Energy of an photosynthesis. Carbon-14 in study of in s, p and d block elements. Amphiprotic elements. orbiting satellite. photosynthesis. 17 hours 10 hours 15 hours
Unit 12AP.2: The nature of matter Stress, strain, Young modulus, strength and Unit 12AB.2: Transport systems Unit 12AC.2: Rates of reaction stiffness. Surface tension and interparticle forces. Blood: structure and function. Tissue fluid and Rate and equilibrium constants. Rate equations. Fluid flow and pressure. Kinetic particle model for lymph. Blood groups and transfusions. Translocation Arrhenius equation. real and ideal gases. Ideal gas equation and and factors affecting transpiration. Xerophytic 10 hours absolute zero. Relationships between pressure, adaptations. molecular speed, kinetic energy and temperature in 12 hours an ideal gas. 15 hours
Unit 12AC.3: Acids and K values Unit 12AB.3: Control, coordination and Acidity, titrations, pH, pKa, Kw, buffers. Ksp. Unit 12AP.3: Thermodynamics homeostasis 7 hours Kelvin and Celsius temperature scales. First law of Endocrine glands and hormone regulation. Structure thermodynamics: energy conservation. and function of kidney. Water balance and Thermodynamic systems: heat, work and internal temperature regulation. Structure and function of energy. Second law of thermodynamics: entropy and neurones and brain. Plant hormones. disorder; efficiency of heat engines. 18 hours 11 hours
Science scheme of work: Grade 12 advanced units 270 hours
2nd semester 146 teaching hours
Biology: 42 hours Chemistry: 53 hours Physics: 51 hours
Unit 12AB.4: Human immune system Unit 12AC.4: Energy and entropy Unit 12AP.4: Oscillations Stem cells and monoclonal antibodies. Immune Born-Haber cycles. Second law of thermodynamics. Free oscillations. Simple harmonic motion: system and allergies. Active and passive immunity Standard entropy and free energy changes. equations and graphs for displacement, velocity, and vaccination. Antibiotics and bacterial resistance. 16 hours acceleration, potential and kinetic energy. Damped Cholera, influenza, malaria and TB. Gene therapy. and forced oscillations. Resonance. 12 hours 9 hours
Unit 12AC.5: Organic reaction mechanisms Shape of aliphatic organic compounds and electronic structure. Electrophilic and nucleophilic reaction Unit 12AB.5: Genetic inheritance Unit 12AP.5: Electrostatic charge and force mechanisms. Dihybrid crosses. Co-dominance and multiple Uniform electric field. Coulomb's law for point 11 hours alleles. Chi-squared test. Human Genome Project. charges. Electric potential, field strength and Genetic fingerprinting, screening and counselling. potential gradient. Electrical and gravitational fields. 9 hours Capacitors: charge and energy; combination in series and in parallel. Unit 12AC.6: Aromatic organic chemistry 13 hours Nomenclature, structure and bonding of aromatic compounds. Arene chemistry. Mechanism of electrophilic substitution and factors affecting it. Unit 12AB.6: Ecological relationships Nitroarenes, amines and azo-compounds. Unit 12AP.6: Quantum and nuclear physics Adaptations of animals to their environment. 11 hours Population growth dynamics. Ecological succession. Emission and absorption spectra. Photoelectric Biological control. Conservation and preservation effect. Quantisation of electron orbital energy. issues. Quantisation of electric charge. Wave-particle 13 hours Unit 12AC.7: Making and using chemicals duality of electrons. Equivalence of mass and Economics of the alkali industry. Industrial processes energy. Schrödinger model of hydrogen atom. versus environment. Exploitation of Qatar's natural 14 hours gas. 7 hours Unit 12AB.7: Biotechnology Genetically engineered human insulin. Biosensors Unit 12AP.7: Astrophysics and cosmology and blood glucose. Monoclonal antibodies. The visible Universe: stars and galaxies; scale and Unit 12AC.8: Macromolecules Immobilised enzymes. structure. Very distant objects: look-back time; Structure and function of amino acids, proteins, 8 hours redshift; universal expansion; the Big Bang; nucleotides and nucleic acids. Relationships between spacetime. Formation and evolution of stars and physical properties of polymers and their structures. planets. Polymer additives, plasticisers, foams. 15 hours 8 hours
GRADE 12A: Biology 1 UNIT 12AB.1 15 hours Biological energetics
About this unit Previous learning Resources
This unit is the first of seven units on biology for To meet the expectations of this unit, students should already be able to The main resources needed for this unit are: Grade 12 advanced. describe the structural features of mitochondria and how these relate to the • overhead projector (OHP), whiteboard The unit is designed to guide your planning and chemical processes of respiration. They should know that ATP is the • yeast culture, thermostatically controlled water baths immediate energy source in cellular processes and be able to relate this to teaching of biology lessons. It provides a link • video clip of a sprint race respiration. They should be able to outline the reaction steps in the between the standards for science and your • models of ATP, ADP and glucose lesson plans. glycolysis, Krebs cycle and oxidative phosphorylation stages of respiration. They should be able to describe the structural features of chloroplasts and • photomicrographs of mitochondria The teaching and learning activities should help know how these relate to the chemical processes of photosynthesis. They • sets of prepared cards (e.g. for glycolysis, Krebs cycle) you to plan the content and pace of lessons. should know that ATP is the immediate energy source in cellular processes • Internet access Adapt the ideas to meet your students’ needs. and be able to relate this to photosynthesis. They should be able to outline • model waterwheel or OHT diagram For consolidation activities, look at the scheme of the reaction steps in the light-dependent and light-independent stages of work for Grades 10A and 11A. • calorimeter photosynthesis. They should be able to relate the structure of a plant leaf to • cabbage, centrifuge, buffer solution, dichlorophenolindophenol You can also supplement the activities with its function in photosynthesis and understand the factors limiting the rate of • chromatography paper and/or thin-layer plates appropriate tasks and exercises from your photosynthesis. school’s textbooks and other resources. • hand spectrometer and strong light source
Introduce the unit to students by summarising Expectations what they will learn and how this builds on earlier Key vocabulary and technical terms work. Review the unit at the end, drawing out the By the end of the unit, students understand the basic biochemistry of Students should understand, use and spell correctly: main learning points, links to other work and real anaerobic respiration and compare this with aerobic respiration. They know world applications. the structure of ATP and ADP, the reactions in the three stages of aerobic • anaerobic respiration, aerobic respiration respiration and the role of NAD and ATP. They understand why aerobic and • glycolysis, the Krebs cycle, oxidative phosphorylation anaerobic respiration yield different amounts of energy in the form of ATP. • pyruvate, lactic acid, fermentation, oxygen debt They understand respiratory quotient and relate this to energy values of • NAD, FAD, ATP, chemiosmosis respiratory substrates. They know the reactions in the two stages of • respiratory quotient photosynthesis and the importance of the Calvin cycle. They know about • light-dependent reactions, light-independent reactions cyclic and non-cyclic photophosphorylation and the use of ATP in the light- • cyclic photophosphorylation, non-cyclic photophosphorylation independent stage of photosynthesis. They know how carbon-14 has been used to investigate photosynthesis. They understand the absorption • photolysis, NADP spectrum of chlorophyll and know that the pigments of chlorophyll can be • carbon-14 separated by chromatography. • absorption spectrum, action spectrum Students who progress further have a more detailed knowledge and • photosystems 1 and 2 deeper understanding of the biochemistry involved in the processes studied. • thylakoid membranes They know that there is more than one form of chlorophyll and that different • chlorophyll pigments forms of chlorophyll have different absorption spectra. They understand the principles of chromatography.
391 | Qatar science scheme of work | Grade 12 advanced | Unit 12AB.1 | Biology 1 © Education Institute 2005 Objectives for the unit Unit 12AB.1
SUPPORTING STANDARDS CORE STANDARDS EXTENSION STANDARDS 15 hours Grade 12 standards
1 hour 11A.5.1 Describe the structure of mitochondria 12A.5.1 Explain how the biochemistry, products and energy release of anaerobic … and relate [this] to the biochemical respiration differ from those of aerobic respiration and how anaerobic Comparing … reactions of respiration … respiration builds up an oxygen debt. anaerobic with aerobic respiration 11A.6.1 Describe the role of ATP as the universal 12A.5.2 Explain the structure and function of ADP and ATP and the synthesis of ATP energy currency in all living organisms in the electron transport chain on the membranes of the mitochondria. 1 hour and relate this to respiration …
ATP: its structure, 11A.6.2 Describe the reaction steps in the three 12A.5.3 Outline glycolysis as the phosphorylation of glucose and the subsequent function and stages of aerobic respiration splitting of hexose phosphate (6C) into two triose phosphate molecules, which synthesis (glycolysis, Krebs cycle and oxidative are further oxidised with a small yield of ATP and reduced NAD. phosphorylation), including the roles of 1 hour oxygen and ATP. 12A.5.4 Explain that when oxygen is available, pyruvate is converted into acetyl coenzyme Glycolysis A (2C), which then combines with oxaloacetate (4C) to form citrate (6C).
12A.5.5 Explain the Krebs cycle as a series of decarboxylation and dehydrogenation 2 hours reactions in the matrix of the mitochondria that reconvert citrate to The ‘link reaction’ oxaloacetate; explain the role of NAD. and the Krebs cycle 12A.5.6 Explain the role of oxygen in the process of oxidative phosphorylation.
2 hours 12A.5.7 Explain respiratory quotient and the relative energy values of carbohydrates, Oxidative proteins and lipids as respiratory substrates.
phosphorylation 11A.5.1 Describe the structure of … 12A.6.1 Explain that energy is transferred by the photoactivation of chlorophyll chloroplasts and link [this] to the resulting in the splitting of water molecules and the transfer of energy to ATP 2 hours biochemical and photochemical and NADPH; that this involves cyclic and non-cyclic photophosphorylation; Respiratory reactions of … photosynthesis. that this generates hydrogen for the light-independent stage of the process; quotients that gaseous oxygen is produced. 11A.6.1 Describe the role of ATP as the 1 hour universal energy currency in all living organisms and relate this to … Biochemistry of photosynthesis. the light-dependent 11A.6.3 Describe the reaction steps in the light- 12A.6.2 Explain that the Calvin cycle involves the light-independent fixation of carbon reaction dependent and light-independent dioxide by combination with RuBP (5C) to form two molecules of GP (3C), that 2 hours stages of photosynthesis, including the ATP and NADP are required for the reduction of GP to carbohydrate, and that role of ATP. RuDP is regenerated. Biochemistry of the light-independent 12A.6.3 Describe how carbon-14 has been used to establish the biochemistry of reaction photosynthesis. 12A.6.4 Know that chlorophyll reflects green light and absorbs in the red and blue areas 3 hours of the spectrum, and that the pigments of chlorophyll can be separated by Light and pigments chromatography.
392 | Qatar science scheme of work | Grade 12 advanced | Unit 12AB.1 | Biology 1 © Education Institute 2005 Activities Unit 12AB.1
Objectives Possible teaching activities Notes School resources
1 hour Introduce this topic by quizzing students on their knowledge of respiration by recalling earlier Use this column to note work, such as that from Unit 11AB.1. Ask students such questions as: your own school’s Comparing anaerobic with • What is respiration? resources, e.g. aerobic respiration • How does the body release the energy in food? And why does the process yield energy? textbooks, worksheets. Explain how the biochemistry, • Why does the body need energy? products and energy release of anaerobic respiration differ Make sure students appreciate that food contains potential energy and the cell systematically from those of aerobic breaks down complex organic molecules that are rich in energy to simpler substances that have respiration and how less energy. Some of the energy released from food can be used to do work while the rest is anaerobic respiration builds released as heat. up an oxygen debt. Ask students to write the word and formula equations for aerobic respiration in animals and plants (recall from Standard 9.8.1). Help them, if necessary, to reproduce the correct equations. Now ask them to explain what the process involves in the cell. Where does it occur? What happens to the sugar, glucose? Try to establish that the glucose is completely oxidised to carbon dioxide and water; compare the process with combustion. Ask them if they think the same combustion process happens inside our cells? Establish that body temperature does not support rapid combustion with oxygen but rather a slower enzyme-regulated process in which the enzymes lower the activation energy (recall from Unit 10AB.3). Glucose is broken down gradually, in a series of steps, with each step catalysed by a different enzyme. Show using an OHT that a large amount of energy is released and one molecule of glucose yields in excess of 30 molecules of ATP. Now compare the process of anaerobic respiration by asking students if they know whether respiration can occur in the absence of oxygen. Prompt them with questions about what happens to the body when you run very fast, and about fermentation. Show them the word and formula equations for anaerobic respiration in animals and plants: lactic acid fermentation and alcohol fermentation, respectively. Explain that most of the potential energy remains in the organic molecules present at the end of the process (lactic acid in animals, alcohol in plants) – the glucose molecule is incompletely oxidised and yields only two molecules of ATP in anaerobic respiration. Also point out that the cell’s supply of the coenzyme NAD would run out (and anaerobic respiration stop) unless there was a stage to regenerate it from NADH as, for example, in the production of lactic acid by reduction of pyruvate. Ask students to work in pairs to investigate the effect of temperature on the rate of fermentation Enquiry skills 12A.1.3, 2A.1.4, 2A.3.1–2A.3.3. in yeast as follows. Use a yeast culture and thermostatically controlled water baths at 20 °C, 35 °C and 50 °C. Invert fermentation tubes full of yeast culture carefully into test-tubes containing10 cm3 of yeast culture into each water bath. Record the length of the carbon dioxide bubble within each fermentation tube at intervals of 10 minutes. Does the rate of fermentation change? Most enzyme-controlled processes double in rate for each 10 °C rise in temperature. Do the results confirm this general rule or not? Visit a bakery to see how fermentation is used in one of the earliest examples of biotechnology. Visit opportunity: Visit a bakery.
393 | Qatar science scheme of work | Grade 12 advanced | Unit 12AB.1 | Biology 1 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
Show students a video of a sprint race and discuss with the class why the athletes breathe heavily for several minutes after the race. Discuss the development of an oxygen debt in the cells, particularly in the muscles of the legs, and show a graph of how the sprint produces a rapid oxygen debt which is repaid when the race is over. Discuss the fate of lactic acid (eventually oxidised by liver). Ask students to produce a chart displaying the reactions in anaerobic respiration. Establish pyruvic acid (pyruvate) as the intermediate metabolite at the cross-roads of anaerobic and aerobic respiration.
1 hour Ask students if they can tell you what ATP is. After establishing its full name and the fact that it is a nucleotide, show a diagram on the OHP to compare it with ADP. Ask students what ATP does in ATP: its structure, the cell. Confirm its status as the intermediary molecule in the cell between the energy-producing function and synthesis reactions and energy-consuming reactions: it is the cell’s ‘energy currency’ molecule. The process Explain the structure and of cell respiration replenishes the ATP supply by powering the phosphorylation of ADP. function of ADP and ATP and Show students models of ATP and ADP. Discuss the potential energy involved in the two the synthesis of ATP in the molecules and how they are interconvertible if inorganic phosphate is available. electron transport chain on the membranes of the Examine photomicrographs of mitochondria from different tissue cells (e.g. liver, skeletal mitochondria. muscle). Ask students to measure them if a scale or magnification is provided. Ask students to draw diagrams of the mitochondria and to find out the names of parts and what their functions are. Explain that ATP can be synthesised in two different ways: either by substrate-level Prepare OHT diagrams. phosphorylation (in glycolysis and the Krebs cycle) or, mainly, by oxidative phosphorylation in Illustrate with a suitable electron microscope the electron transport chain. Show students a diagram of the crista (inner mitochondrial picture. membrane) with a portion showing the electron transport chain and the enzyme ATP synthase
and explain the chemiosmotic process of ATP synthesis. (See further details of chemiosmosis in oxidative phosphorylation later.)
1 hour Recall introductory work on the biochemistry of respiration (e.g. in Unit 11AB.1). Glycolysis Introduce the biochemistry by giving an overview of the whole process in outline so students can appreciate that glycolysis is just the first stage of three main stages: glycolysis, the Krebs Outline glycolysis as the cycle and oxidative phosphorylation. Ask students to find out where each of the stages occurs phosphorylation of glucose in the cell. and the subsequent splitting of hexose phosphate (6C) Use a molecular model of glucose to demonstrate its structure while explaining glycolysis. into two triose phosphate Tell students that the word glycolysis means ‘splitting of sugar’ and that is exactly what happens molecules, which are further in this pathway: the six-carbon sugar, glucose, is split into two three-carbon sugars. These oxidised with a small yield of smaller sugars are then oxidised and the remaining atoms rearranged to form two molecules of ATP and reduced NAD. pyruvate. Show this on the OHP or build up on the whiteboard. Give more details of glycolysis. Show that glucose must first be activated by two ATP molecules which phosphorylate the glucose to hexose diphosphate (6C). This is then split into two triose phosphate molecules. The trioses are then oxidised in an energy-yielding phase to produce two molecules of pyruvate and four ATP molecules (but only two net, see above) and two reduced NAD molecules.
394 | Qatar science scheme of work | Grade 12 advanced | Unit 12AB.1 | Biology 1 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
Ask students to carry out a card-sort activity that requires them to put the intermediates of the Prepare sets of cards for students to sort. glycolytic pathway (e.g. glucose, glucose phosphate, ADP + Pi, NAD, ATP, hexose diphosphate) in the correct order. Divide the class into two teams and challenge students to see who can produce the quickest solution. The first team to finish may not win if they have taken less care with accuracy.
2 hours Tell students that when oxygen is present, the pyruvate enters the mitochondria for the aerobic stages of respiration: the Krebs cycle and oxidative phosphorylation. The pyruvate still contains The ‘link reaction’ and the most of the energy from the glucose. Krebs cycle Show students a summary diagram of the Krebs cycle, including the ‘link reaction’ from Prepare OHT diagram and copies for students. Explain that when oxygen is pyruvate to acetyl coenzyme A. Give them a copy. Ask them to study what is happening and available, pyruvate is then ask one student to explain the link reaction (this is the junction between glycolysis and the converted into acetyl Krebs cycle). Make sure students know that this is the first step in aerobic respiration where coenzyme A (2C), which then + CO2 is released. The pyruvate is also oxidised (NAD is reduced to NADH) to an acetyl group combines with oxaloacetate and combined with a coenzyme, coenzyme A, to activate the remaining molecule to acetyl (4C) to form citrate (6C). coenzyme A. The acetyl coenzyme A then feeds its two-carbon molecule into the Krebs cycle Explain the Krebs cycle as a by adding to the four-carbon compound oxaloacetate to form the six-carbon citrate. series of decarboxylation and Ask students to find out about coenzymes using the Internet. ICT opportunity: Use of the Internet. dehydrogenation reactions in the matrix of the mitochondria Ask students, in turn, to tell the rest of the class something about the reactions in the Krebs that reconvert citrate to cycle (e.g. eight steps; take place in mitochondrial matrix; each involving a specific enzyme; oxaloacetate; explain the role reactions include a sequence of decarboxylations and dehydrogenations; oxidation of the of NAD. organic acids in the cycle results from production of reduced coenzymes: NADH and FADH; production of ATP by substrate phosphorylation; oxaloacetate is regenerated, which can then accept another two-carbon acetyl coenzyme A for another turn of the cycle).
Ask students to summarise the total numbers of CO2, NADH and FADH molecules produced in
one turn of the Krebs cycle, including the link reaction, starting from pyruvate (three CO2, four NADH and one FADH from each pyruvate molecule). Ask students what has been the fate of each pyruvate? (They have been oxidised to release
three CO2 and reduced coenzymes, as above.) Ask students to carry out a card-sort activity that requires them to put the intermediates of the Prepare sets of cards for students to sort. Krebs cycle in the correct order. Divide the class into two teams and challenge students to see who can produce the quickest solution. The first team to finish may not win if they have taken less care with accuracy. Encourage students to find out about Hans Krebs and why a series of reactions is named after ICT opportunity: Use of the Internet. him.
395 | Qatar science scheme of work | Grade 12 advanced | Unit 12AB.1 | Biology 1 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
2 hours Ask students where the energy that was in the pyruvate molecule has gone (most is still in the reduced coenzymes). Oxidative phosphorylation Ask students how much energy in the form of ATP molecules has been produced from the Explain the role of oxygen in original glucose molecule (four by substrate-level phosphorylation: two from glycolysis and two the process of oxidative from the Krebs cycle). phosphorylation. Tell students that the final stage of aerobic respiration is oxidative phosphorylation which, coupled to the electron transport chain, powers the production of most of the ATP molecules produced in respiration. This is a difficult concept for students to understand; using the following waterfall analogy may Prepare a suitable OHT diagram, or use a help. Show students, on the OHP or board, a diagram of a series of waterfalls with water model. flowing. Now add the ‘inflowing molecules’ (NADH) and show by arrows the downward flow of molecules to the next level (FADH) and then further arrows down to other molecules in turn, such as cytochromes b, then c and then a, and finally, at the very bottom, oxygen. The above analogy can illustrate the gradual release of energy that the real electron transport chain achieves by being arranged sequentially in the inner mitochondrial membrane at successively lower energy levels. Ask students how the mitochondrion couples this (electron transport) process to ATP synthesis. The answer is a mechanism called chemiosmosis. Show students a diagram of the crista (inner mitochondrial membrane) with a portion showing Prepare an OHT diagram. the electron transport chain and the membrane protein, the enzyme ATP synthase, and explain the chemiosmotic process of ATP synthesis. (Explain how an ion gradient of H+ is created by the electron chain pumping H+ into the intermembrane space. The H+ then diffuses down the proton gradient through the membrane protein channels, which are protein complexes called ATP synthases, and this ‘fall’ of H+ drives the phosphorylation of ADP to ATP.) Ask students what the relationship is between the reduced coenzymes NADH and FADH and the number of ATP molecules produced (each NADH that enters the electron transport chain generates a maximum of three ATP molecules and each FADH, with less energy, produces a maximum of two ATP molecules). Ask students to use their textbook or the Internet to find information on energy production and ICT opportunity: Use of the Internet. then to work out the total energy production (as ATP molecules) from one glucose molecule. Ask them to draw up a summary table to show where all the energy-containing molecules (NADH, FADH, ATP) are produced. Compare aerobic and anaerobic ATP yields. They should arrive at a figure of around 36 ATP molecules produced during aerobic respiration. (The ‘mitochondrial shunt’ or ‘shuttle’ has to be taken into account, in which the two NADH molecules from glycolysis enter the mitochondria but, because of some losses, these produce an average of four ATP molecules and not the expected six ATP from oxidative phosphorylation.) A figure of just two ATP molecules produced during anaerobic respiration shows that aerobic respiration yields 18 times more ATP than fermentation. Ask students to produce a wall chart of the biochemistry of respiration. Enquiry skill 12A.3.4
396 | Qatar science scheme of work | Grade 12 advanced | Unit 12AB.1 | Biology 1 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
2 hours Ask students whether glucose is the sole substrate in respiration. Their answers should indicate that lipids and even proteins can act as substrates as well as other carbohydrates. Respiratory quotients Ask students to find out the energy value of different respiratory substrates from their textbook ICT opportunity: Use of the Internet. Explain respiratory quotient or from the library or Internet. and the relative energy values of carbohydrates, Demonstrate how the energy value of a substrate is determined by burning a known mass of Use a simple calorimeter with a supply of proteins and lipids as the substance in pure oxygen in a calorimeter. Knowledge of the calorimeter’s water equivalent oxygen respiratory substrates. will be required to carry out the calculation. Record the temperature at the start and when it Enquiry skills 12A.1.1, 12A.3.1, 12A.3.3 reaches its maximum, and use these to calculate the substrate’s energy content. Use different
substrates and compare the values. The values obtained may be significantly less than given in the official tables. Ask students to explain. The loss of heat to the surroundings is the main reason for the difference. Ask students to write down the simple equation for the aerobic respiration of glucose:
C6H12O6 + 6O2 ⇒ 6CO2 + 6H2O + energy
Ask them to work out the ratio of O2 taken in to the volume of CO2 released; a ratio of 1:1 is
produced by 6CO2 given out compared with 6O2 taken in. However, different substrates will give different ratios of the volumes of oxygen used and carbon dioxide given off. Measuring this ratio produces the respiratory quotient (RQ) and this indicates what substrate is being used in respiration. Ask students what the RQ of glucose is (6/6 = 1.0). The aerobic respiration of the fatty acid oleic acid produces the following equation:
C18H34O2 + 25.5O2 ⇒ 18CO2 + 17H2O + energy Ask students to work out its RQ (18/25.5 = 0.7). Ask students what happens to the RQ when the respiration is anaerobic.
C6H12O6 ⇒ 2C2H5OH + 2CO2 + energy (RQ = 2/0 = infinity, although in reality some respiration is likely to be aerobic so a small volume
of O2 will be taken up so the RQ will be above 2.)
1 hour Ask students to use the Internet to find out about the work of Robert Hill at Cambridge on ICT opportunity: Use of the Internet. chloroplasts and C.B. van Niel at Stanford University on photosynthesis in bacteria. Biochemistry of the light Enquiry skill 12A.2.1 dependent reaction Describe the discovery by Robert Hill that isolated chloroplasts can evolve oxygen if provided with light, water and a suitable hydrogen acceptor. Ask students what conclusions can be drawn Explain that energy is from this ‘Hill reaction’. transferred by the photoactivation of chlorophyll The possible conclusions are: resulting in the splitting of water • oxygen production requires light; molecules and the transfer of • oxygen comes from water and not from carbon dioxide; energy to ATP and NADPH; • chloroplasts can produce oxygen without other cell components; that this involves cyclic and non- • a hydrogen acceptor molecule is needed. cyclic photophosphorylation; Ask students what happens to water in this light-dependent reaction. that this generates hydrogen for the light-independent stage of The answer is that chloroplasts split water molecules using light energy (photolysis) and so the the process; that gaseous simple equation for photosynthesis that suggests carbon dioxide as the source of oxygen needs oxygen is produced. to be rewritten.
397 | Qatar science scheme of work | Grade 12 advanced | Unit 12AB.1 | Biology 1 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
To describe the reaction steps, use an OHT or whiteboard to illustrate: • how the absorption of light affects the photosynthetic pigments, especially chlorophyll; • that, in the thylakoid membranes of the chloroplast, electrons from the two chlorophyll photosystems are each raised to a higher energy level. During the light reactions there are two possible routes for electron flow: a cyclic route and a non-cyclic route, which both result in photophosphorylation. Ask students to produce a flow chart of the processes of: • cyclic photophosphorylation; • non-cyclic photophosphorylation. Cyclic photophosphorylation Explain that this is the simpler pathway and involves only photosystem 1 and produces only ATP. The electrons from the photoactivated chlorophyll molecule from photosystem 1 are passed along the electron transport chain in the thylakoid membrane, during which energy is released and used to synthesise ATP from ADP and inorganic phosphate (very similar to chemiosmosis in mitochondria explained earlier in this unit). This process is known as cyclic photophosphorylation since the same electrons that left the chlorophyll return to it again. Non-cyclic photophosphorylation Explain that this electron pathway involves the cooperation of both photosystems (in the familiar
‘Z scheme’) and results in the production of both ATP and NADPH, as well as the release of O2. The electrons from the photoactivated chlorophyll molecule from photosystem 1 are captured by an electron acceptor and used to reduce NADP. Electrons from the photoactivated chlorophyll molecule from photosystem 2 are used to stabilise photosystem 1 and produce ATP by passing along the same electron path as described in the non-cyclic path above. The photosystem 2 chlorophyll’s lost electrons are replaced by those from the splitting of water (photolysis), resulting in the release of oxygen gas and hydrogen ions. The electrons that have passed along the electron transport chain are used, together with the hydrogen ions, to reduce NADP to NADPH. Demonstrate the Hill reaction by the following procedure (or ask small groups of students to You will need dark green leaves (e.g. cabbage carry out the procedure). Extract chloroplasts from cabbage leaves and isolate them. Then add leaves), chilled sucrose/phosphate buffer at them to the blue dye DCPIP (dichlorophenol-indophenol), expose the mixture to light and note pH 6.5, and a bench centrifuge. the change of colour from blue to colourless. This occurs because the blue dye is readily Enquiry skills 12A.1.3, 12A.4.1 reduced to a colourless compound by reducing agents.
398 | Qatar science scheme of work | Grade 12 advanced | Unit 12AB.1 | Biology 1 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
2 hours Use the OHP or board to outline the light-independent reactions that take place in the stroma of Biochemistry of the light the chloroplasts. Carbon dioxide from the atmosphere is fixed using ATP and reduced NADP from the light-dependent reaction. Carbon dioxide is reduced to carbohydrate. independent reaction Ask students to investigate on the Internet how Melvin Calvin helped contribute to our ICT opportunity: Use of the Internet. Explain that the Calvin cycle understanding of photosynthesis. involves the light-independent fixation of carbon dioxide by Teach students about the experimental investigations carried out by Calvin as follows. combination with RuBP (5C) • Use the OHP to show students Calvin’s ‘lollipop’ apparatus, which he used to feed single- Prepare suitable OHTs. to form two molecules of GP celled algae carbon-14 labelled carbon dioxide for progressively longer light periods. (3C), that ATP and NADP are • Use the OHP to show students Calvin’s two-dimensional chromatography technique required for the reduction of separating the carbon-14 labelled products and developed to display a radiochromatogram. GP to carbohydrate, and that • Ask students to work in pairs to arrange a set of cards in the correct sequence displaying the Write out sets of suitable cards: a simple set and RuDP is regenerated. events of the Calvin cycle. Each card should have only a single reaction described or a single a more complex set. Describe how carbon-14 has chemical intermediate or even enzyme named (e.g. ribulose bisphosphate carboxylase – the been used to establish the commonest enzyme in the world). Begin by using a simple set of cards showing just the biochemistry of number of carbon atoms in each compound rather than names of compounds. Then add photosynthesis. more detailed cards for more advanced students as required. • Create a set of OHT cutout shapes of the events of the Calvin cycle, as described above, and build the cycle up sequentially on the OHP, with a logical progression and explanation. • Provide students with a template of the Calvin cycle with blank boxes to be filled with the Prepare OHT cutout shapes of Calvin cycle names of the intermediates. Either ask students to complete the exercise from their own components. research or use the template in conjunction with the card activity above. Prepare a Calvin cycle template. Ask students to identify the way that the light-dependent reaction helps the light-independent reaction (through ATP and reduced NADP).
3 hours Ask students to work in pairs to extract the pigments from leaves and carry out a leaf pigment Students will need chromatography paper or separation and identification by a chromatographic technique. This could be either previously made up thin-layer plates of silica gel Light and pigments • paper chromatography on microscope slides. Know that chlorophyll reflects
green light and absorbs in the or red and blue areas of the • thin-layer chromatography. spectrum, and that the Demonstrate the absorption of light by plant pigments by shining a light through a solution of the You will need a hand-held spectrometer. pigments of chlorophyll can pigments and observing the transmitted light using a spectrometer (red and blue spectral be separated by regions may appear black but the green region will be seen clearly because this is not absorbed chromatography. but reflected). Show students an OHT of an absorption spectrum of the plant pigments and ask them to Prepare OHTs of an absorption spectrum and explain its shape. an action spectrum for photosynthesis. Show students an action spectrum of photosynthesis and ask them to explain its shape. Demonstrate fluorescence. Shine a strong light onto a tube of extracted pigment and turn all the Use a projector lamp as the strong light source. lights out; the chlorophyll solution will fluoresce deep red in the darkened room.
399 | Qatar science scheme of work | Grade 12 advanced | Unit 12AB.1 | Biology 1 © Education Institute 2005 Assessment Unit 12AB.1
Examples of assessment tasks and questions Notes School resources
Assessment Explain what the term oxygen debt means and how such a debt is produced.
Set up activities that allow a. Explain the process of glycolysis and lactic acid production. students to demonstrate what b. What is the fate of lactic acid when aerobic conditions return? they have learned in this unit. The activities can be provided Calculate the number of reduced NAD and FAD molecules produced by each glucose molecule
informally or formally during entering the respiratory pathway when oxygen is available. and at the end of the unit, or
for homework. They can be Explain how ATP is produced by electron transport and oxidative phosphorylation. selected from the teaching Explain the processes of: activities or can be new a. cyclic photophosphorylation; experiences. Choose tasks and questions from the b. non-cyclic photophosphorylation. examples to incorporate in a. Complete the spaces in the diagram of the Calvin cycle. Provide a suitable diagram of the Calvin cycle to the activities. b. Explain how the reactions of the light-dependent stage help the reactions of the light- be completed by students. independent stage of photosynthesis.
400 | Qatar science scheme of work | Grade 12 advanced | Unit 12AB.1 | Biology 1 © Education Institute 2005 GRADE 12A: Biology 2 UNIT 12AB.2 12 hours Transport systems
About this unit Previous learning Resources
This unit is the second of seven units on biology To meet the expectations of this unit, students should already be able to The main resources needed for this unit are: for Grade 12 advanced. explain why multicellular animals need a transport system for respiratory • microscopes, eyepiece graticule, stage micrometer The unit is designed to guide your planning and gases, water, food and waste, and describe the structure and function of the • microscope slides of blood and leaves human circulatory system. They should understand the need for a transport teaching of biology lessons. It provides a link • animal blood system in multicellular plants. They should recall the structure, function and between the standards for science and your • haemocytometer lesson plans. distribution of phloem and xylem in dicotyledonous plants, and be able to describe translocation and transpiration. • video camera and monitor, digital camera The teaching and learning activities should help • overhead projector (OHP) you to plan the content and pace of lessons. • prepared OHTs and sets of cards on blood and body fluids Adapt the ideas to meet your students’ needs. Expectations • template shapes of red blood cells For consolidation activities, look at the scheme of work for Grades 10A and 11A. By the end of the unit, students know the structure and functions of red • potometers, leafy shoots, electric fan, polythene bag and white blood cells and the role of blood, fluid tissue and lymph in • autoradiographs of plants You can also supplement the activities with transport. They understand the roles of the constituents of blood in the appropriate tasks and exercises from your • Internet access transport of oxygen and carbon dioxide. They know the human blood groups school’s textbooks and other resources. and their significance. They know that organic materials are transported in Introduce the unit to students by summarising plant phloem by translocation and that there are several hypotheses to Key vocabulary and technical terms what they will learn and how this builds on earlier explain the mechanism. They understand the factors affecting the rate of Students should understand, use and spell correctly: work. Review the unit at the end, drawing out the transpiration and the adaptations of xerophytic plants for water conservation main learning points, links to other work and real • phagocyte, monocyte, neutrophil, lymphocyte Students who progress further have a more detailed knowledge and world applications. • haemoglobin, carbonic anhydrase understanding of oxygen transport by reference to such additional aspects as foetal haemoglobin and muscle myoglobin. They understand the Rhesus • dissociation curves, Bohr effect blood group and the complications associated with Rhesus factor in • blood groups, transfusions, antigens, antibodies pregnancy. They also have a more detailed understanding of xerophytic • stomatal pores, guard cells plants. • xerophytes, xerophytic features • translocation, mass flow, pressure flow • chemiosmotic • autoradiography • crassulacean acid metabolism • electro-osmotic • transcellular
401 | Qatar science scheme of work | Grade 12 advanced | Unit 12AB.2 | Biology 2 © Education Institute 2005 Objectives for the unit Unit 12AB.2
SUPPORTING STANDARDS CORE STANDARDS EXTENSION STANDARDS 12 hours Grade 12 standards
4 hours 10A.9.6 Know that red blood cells carry 12A.7.1 Explain the structure and function of human red blood cells, phagocytes oxygen. and lymphocytes and the differences between the functions of blood, tissue Blood: its fluid and lymph in the transportation of substances to and from cells. structure and 10A.9.1 Explain why large animals need transport transport systems for respiratory functions gases, water, food and waste in terms of their surface to volume ratio. 1 hour 12A.7.2 Know the composition of the blood and explain the roles of red cells, Blood groups plasma, haemoglobin and carbonic anhydrase in the transportation of and transfusions oxygen and carbon dioxide.
12A.7.3 Describe and explain the significance of the dissociation curves of 4 hours haemoglobin at different carbon dioxide levels (the Bohr effect). Factors affecting 12A.7.4 Know that human blood can be classified into one of four groups and the transpiration implications of this for blood transfusions.
12A8.1 Explain how temperature, wind speed and humidity affect the rate of 1 hour transpiration and how plants control their water loss by regulating stomatal Xerophytic opening. adaptations 12A.8.2 Explain some of the adaptations that help xerophytic plants to conserve
water. 2 hours 11A.8.4 Describe the processes of 12A.8.3 Explain some of the hypotheses being put forward to explain translocation. Translocation translocation of photosynthetic hypotheses products in the phloem and transpiration of water and dissolved minerals in the xylem.
12A.8.4 Know how autoradiography and aphids have been used in the study of translocation.
402 | Qatar science scheme of work | Grade 12 advanced | Unit 12AB.2 | Biology 2 © Education Institute 2005 Activities Unit 12AB.2
Objectives Possible teaching activities Notes School resources
4 hours Ask students, individually, to examine human blood smears under the microscope at high Students will need microscopes and blood Use this column to note magnification and to produce diagrams of samples of cells observed. smears on slides. your own school’s Blood: its structure and resources, e.g. transport functions Use the video camera attachment to the microscope to display blood cells on a monitor. Ask You need to set up a video camera attachment students to identify the types of cells: red blood cells, phagocytes (neutrophils and to the microscope. textbooks, worksheets. Explain the structure and monocytes/ macrophages) and lymphocytes by reference to appearance and relative size. function of human red blood You will need a microscope with eyepiece cells, phagocytes and Ask students to measure the sizes of the blood cells using microscopes fitted with an eyepiece graticule. You may also need a stage lymphocytes and the graticule. micrometer if the microscope is not already differences between the Provide sets of cards with the names of the blood cells on one set and their functions on calibrated. functions of blood, tissue fluid another set. Ask students to match the cards. Prepare cards of blood cells and their functions. and lymph in the Give students a table like the one below and ask them to complete it. transportation of substances
to and from cells. Red blood Phagocytes (neutrophils and Lymphocytes Know the composition of the cells monocytes/macrophages) blood and explain the roles of Structure red cells, plasma, Function haemoglobin and carbonic anhydrase in the Site of
transportation of oxygen and production
carbon dioxide. Describe and explain the Show students large diagrams, using the OHP or interactive whiteboard, of each of the blood significance of the cells and discuss their structures and functions in turn. dissociation curves of Provide sets of cards with the names of the body fluids (blood plasma, tissue fluid and lymph) Prepare cards of fluids and their functions. haemoglobin at different on one set and their functions on another set. Ask students to match the cards. carbon dioxide levels (the Show students a diagram of a capillary bed also including a lymphatic and ask them to explain Bohr effect). how tissue fluid is formed and removed by reference to blood hydrostatic pressure and osmotic pressure. Also explain how lymph is produced. Ask students to compare the composition of the blood plasma, tissue fluid and lymph. Ask a nurse to visit the class to talk about blood tests. Arrange for a visit by a nurse. Ask students to produce a flow chart or a table illustrating all the components of blood, including brief details of the structure, numbers and functions of each of the blood cells. Ask students to construct a pie chart of the composition of human blood. Use a centrifuge to separate the components of animal blood and examine the result. Use a laboratory centrifuge to spin the blood to Ask students to describe how the red blood cell is adapted for the transport of oxygen. (Small find the relative proportion of cells and plasma size and short diffusion distance; biconcave disc shape increases surface area to volume ratio; Enquiry skill 12A.4.1 no nucleus, mitochondria or endoplasmic reticulum means more haemoglobin; haemoglobin combines readily with oxygen and releases oxygen readily according to the diffusion gradient in
the lungs or tissues, respectively.)
403 | Qatar science scheme of work | Grade 12 advanced | Unit 12AB.2 | Biology 2 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
Ask students ‘What additional property enables the red cell to be adapted to transporting carbon dioxide?’ (The presence of the enzyme carbonic anhydrase to produce hydrogencarbonate ions, HCO–, and the presence of haemoglobin to mop up H+ from solution to maintain the pH of the blood.) Recall the protein structure of haemoglobin from Unit 10FB.1. Show a computer animation or an OHT diagram of the haemoglobin molecule. Ask students to write the equation for the combination of haemoglobin with oxygen and explain why each haemoglobin combines with four oxygen molecules. Ask students to write the equation for the combination of carbon dioxide and water with the enzyme carbonic anhydrase to show the production of hydrogencarbonate ions, HCO–, and hydrogen ions, H+, in a red blood cell. Ask students to explain the ways that carbon dioxide is transported. (Around 85% as hydrogencarbonate ions, HCO–, carried in the plasma after diffusing out of the red blood cells, 10% combined with haemoglobin as carbamino-haemoglobin, and 5% dissolved in the plasma.) Ask students to produce a large diagram of a red blood cell in the capillary next to some respiring cells and show all the reactions associated with the transport of carbon dioxide. Give students a copy of a dissociation curve for haemoglobin at one carbon dioxide Source a typical oxygen dissociation curve from concentration. Use an OHT of the diagram to explain its sigmoid shape by reference to: a suitable textbook, and produce an OHT. • haemoglobin’s high affinity for oxygen at the high partial pressures of oxygen encountered in the lungs; • haemoglobin’s equally important property of releasing oxygen as the partial pressure of oxygen falls in the tissues. Explain that the area to the right and beneath the graph represents the proportion of oxyhaemoglobin compared with free haemoglobin and oxygen to the left of the graph. Explain that the steepness of the graph at lower partial pressure of oxygen corresponds with small changes in the tissues, which therefore promotes the release of significant supplies of oxygen where it is needed. Ask students to find out using their textbook, the library or the Internet how the dissociation ICT opportunity: Use of the Internet. curve is affected by the body’s carbon dioxide level. Discuss their answers; use an OHT overlay on the original dissociation curve showing the new curve displaced to the right. Clarify the discussion by explaining the Bohr effect. Ensure they all understand the adaptive nature of this response to increased carbon dioxide in causing the shift of the curve to the right and therefore releasing more oxygen at a particular oxygen partial pressure. Give students a copy of a dissociation curve for haemoglobin at one carbon dioxide Source a copy of a dissociation curve for concentration. Ask them to write an explanation of the shape of the curve. Ask them to add two haemoglobin more curves to show what happens at carbon dioxide levels above and below the original graph and then ask them to explain the curves’ positions and what circumstances in the body may have produced such curves. Give students an incomplete account of the Bohr effect and ask them to add the most Write an account explaining the Bohr effect with appropriate words in the spaces. blank spaces for students to fill in.
404 | Qatar science scheme of work | Grade 12 advanced | Unit 12AB.2 | Biology 2 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
1 hour Quiz students to see how much they already know about blood groups (e.g. they may know about transfusions from their own family or from medical knowledge obtained through the media Blood groups and or reading). transfusions Use the OHP to show a sample red blood cell from each of the four groups, A, B, AB and O, Prepare an OHT with diagrams of the ABO Know that human blood can displaying the antigens A and B as appropriate. Add an overlay, where appropriate, to show blood groups. be classified into one of four complementary plasma antibodies. groups and the implications of this for blood transfusions. Explain the possession of antigens A or B and also antibodies anti-A or anti-B. Use the OHP to display large template shapes of the red blood cells with their antigens shown as a Prepare OHT templates of red blood cells with specific shape on the membrane’s surface. Add complementary shapes that fit the antigens to specific shapes for A and B antigens and represent the corresponding antibodies (i.e. make anti-A fit into antigen A, and make anti-B fit into additional templates of specific complementary antigen B). Use the shapes to explain the normal combinations for each blood group (e.g. blood shaped anti-A and anti-B antibodies. group A has A antigens with anti-B antibodies, which do not fit each other’s shapes). Give students, working in pairs, sets of cards with either antigens or antibodies and ask them to Prepare sets of suitable cards with ‘antigen A’, arrange them in the correct combinations to represent the four blood groups. ‘antigen B’ or ‘no antigen’ written on each card Tell students that the first blood transfusions were risky and many patients died. Ask them to in one set and ‘anti-A antibody’, ‘anti-B antibody’ pretend they are the nurse or doctor who has to select the correct bag of donor’s blood for a or ‘no antibodies’ written on each card in the patient. Ask them to complete a table showing which transfusions are compatible and which are other set. not compatible. Divide the class into teams and see who correctly completes the exercise first. Prepare a table of transfusions on OHT. This will not necessarily be the first team to finish. Enquiry skill 12A.3.4 Play a game with blood groups cards in which individuals requiring a transfusion must find others Use the same cards as described in the blood who can be a donor while potential donors must find individuals who could receive their blood. group task above.
4 hours Recall students’ understanding of transpiration covered in the earlier Unit 11AB.2 by having a Refer to Unit 11AB.2 on transpiration. quiz session. Factors affecting transpiration Ask students to suggest environmental factors that might affect the rate of transpiration. Investigate the influence of various environmental factors on the rate of transpiration by using a Explain how temperature, potometer. Organise students to work in pairs for the following activities. wind speed and humidity affect the rate of transpiration Temperature and how plants control their Raise the temperature by placing the plant progressively nearer to a heat source and take the Each pair of students will need a potometer with water loss by regulating temperature with a thermometer (e.g. move the plant closer to a radiator) and measure the a leafy shoot attached for each of these stomatal opening. plant’s rate of water uptake with the potometer. activities. Take care to avoid air bubbles in the Ask students to explain the results, which are expected to show that an increase in the stems by cutting the stems under water and temperature in the immediate vicinity of the leaves causes an increase in the rate of rapidly inserting them in the water-filled transpiration potometers. Explain the effect of temperature on the rate of transpiration by reference to the fact that the Enquiry skills 12A.1.1–12A.1.3, 12A.3.1– addition of heat causes an increase in the rate of movement of the water molecules in the water 12A.3.3, 12A.4.1, 12A.4.2 vapour around the leaf. Explain that water passes by the apoplast and symplast pathways to the mesophyll cells before evaporating into the sub-stomatal air spaces. Make sure students understand that the removal of water from the xylem in the veins of the leaf creates a pulling The cohesion-tension theory is referred to in force, which draws water up the plant’s stem by the cohesion-tension theory. Unit 11AB.2.
405 | Qatar science scheme of work | Grade 12 advanced | Unit 12AB.2 | Biology 2 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
Wind speed Change the wind speed by using an electric fan at a range of different speeds and/or different Enquiry skills 12A.1.1–12A.1.3, 12A.3.1– distances from the plant stem in the potometer. 12A.3.3, 12A.4.1, 12A.4.2 Ask students to explain the results, which are expected to show that an increase in the wind speed in the immediate vicinity of the leaves causes an increase in the rate of transpiration. Make sure students understand that the movement of air across the leaf surfaces causes an increase in the rate of movement of the water molecules in the water vapour in the boundary layer around the leaf. The humid air in the vicinity of the leaf is moved away more quickly as the wind speed is increased. Provide students with a partly completed explanation of the experiment; ask them to fill in the Prepare a partly completed explanation of the blank spaces with the appropriate words. experiment.
Humidity Change the humidity by placing a large polythene bag over the plant and measuring the plant’s Enquiry skills 12A.1.1–12A.1.3, 12A.3.1– rate of water uptake using the potometer. Compared the result with that from a control set of 12A.3.3, 12A.4.1, 12A.4.2 apparatus without the polythene bag. Ask students to explain the results, which are expected to show that an increase in the humidity in the immediate vicinity of the leaves causes a decrease in the rate of transpiration Make sure students understand that the boundary layer of water vapour around the leaf deepens. The humid air in the vicinity of the leaf is not moved away. Provide students with a partly completed explanation of the experiment; ask them to fill in the Prepare a partly completed explanation of the blank spaces with the appropriate words. experiment. Ask students to use their textbooks or the Internet to find out how the stomatal pores regulate ICT opportunity: Use of the Internet. the water loss from the leaves.
Make sure students understand that the specialised guard cells control the opening and closing of the stomatal pores. Explain that several factors influence the opening and closing of stomata. These include light, the availability of water and the supply of respiratory substrates. Stomata even display a diurnal rhythm in which they normally open by day and close at night. Ask students to use their textbooks or the Internet to help them explain the chemiosmotic mechanism of stomatal opening and closing. Make sure students understand that the chemiosmotic mechanism of stomatal opening and closing suggests that hydrogen ions are first removed from the guard cells by a proton pump. This develops an electrochemical gradient across the guard cell membrane causing potassium ions to diffuse in, accompanied by electronegative chloride ions. The increased solute concentration causes the water movement into the guard cell by osmosis. The guard cells become turgid and the stomatal pore opens. An exodus of potassium ions from the guard cells causes the stomatal closure. Ask students, working singly or in pairs, to use a microscope to study slides of the cross- Students will need: microscopes, prepared leaf sections of leaves with open and closed stomata. cross-sections, fresh dicotyledonous leaves, nail varnish, haemocytometers.
406 | Qatar science scheme of work | Grade 12 advanced | Unit 12AB.2 | Biology 2 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
Ask students, working singly or in pairs, to use a microscope to examine leaf impressions of Enquiry skills12A.3.1–12A.3.3, 12A.4.1 stomata in the epidermis of leaves. Paint a small area (e.g. 5 mm2) of the underside of a dicotyledonous leaf with a thin layer of nail varnish. Allow the varnish to dry and carefully remove it with forceps. Turn it over on the surface of a slide and examine it under the microscope. Compare different species and surfaces.
Ask students, working singly or in pairs, to count the number of stomata by mounting such a leaf impression on a haemocytometer grid and examine under high power of the microscope. Focusing simultaneously on the grid and impression, the number of stomata can be counted for a measured area.
1 hour Explain that xerophytes are plants adapted for arid conditions, such as those found in Qatar. Xerophytic adaptations Ask students to find out about the adaptations displayed by xerophytes, using their textbooks or ICT opportunity: Use of the Internet. the Internet. Explain some of the adaptations that help Ask students to make a photographic record of the xerophytic adaptations of the plants of Qatar A digital camera would be most useful for this xerophytic plants to conserve by visiting a suitable location (e.g. a park or garden). activity. water. Provide samples of common plants of Qatar, perhaps growing in plant pots, to allow students to Visit opportunity: Visit a park or garden. investigate leaf and stem structure in the laboratory. Grow plants or obtain them locally. Give students opportunities to study plants from different environments (e.g. desert or Make specimen plants available or arrange a seashore) and ask them to compare the leaf structures. site visit. Adaptations of the leaves and stems of xerophytes are the most readily observed features. Ask students questions to encourage them to explain their observations about the xerophytes in each case. For example, why do some xerophytes have: • small thick leaves or rolled leaves? (Water loss limited by reducing exposed surface area to volume.) • leaves reduced to spines? (Water loss limited from reduced surface area of leaves.) • a thick cuticle? (The wax is impermeable to water so reduces transpiration.) • stomata concentrated on lower leaf surface and recessed into depressions? (Water loss limited by being away from direct sunlight and diffusion gradients of water vapour are maintained to limit transpiration.) • leaves that are shed in driest months (some desert plants)? (Transpiration significantly reduced during the time when water is unavailable.) • leaves covered in hairs? (Water loss limited by the maintenance of the water vapour concentrations in the vicinity of the leaf surface, air movement is reduced so the rate of transpiration is reduced.) • fleshy stems? (Water stored in the rainy season can enable survival in the dry season. These modified stems are the photosynthetic organs of cacti; the leaves are spines). Ask students to use the Internet to find out about the adaptations of the succulent plants of the ICT opportunity: Use the Internet. Crassulaceae family. These plants, together with a few others, including pineapples, assimilate their carbon dioxide through a different metabolic pathway: the ‘crassulacean acid metabolism’ (they are known as CAM plants). These plants open their stomata at night and close them in the day when transpiration would normally be at its height.
407 | Qatar science scheme of work | Grade 12 advanced | Unit 12AB.2 | Biology 2 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
2 hours Recall the structure of the phloem by giving students a quiz. Alternatively, give students a task Recall unit11AB.2. Prepare a suitable phloem sheet containing a phloem diagram with incomplete labels and sentences, and ask them to fill in diagram and task sheet. Translocation hypotheses the missing words. Explain some of the Ask students to outline the main features of translocation. hypotheses being put forward to explain translocation. Explain that the phloem transports the organic products of photosynthesis, mainly sucrose, by a process called translocation. In contrast to the xylem’s one-way transport, the phloem sap Know how autoradiography travels in two directions. Introduce students to the evidence for phloem translocation using the and aphids have been used suggestions below. in the study of translocation. Evidence for phloem translocation Ask students to use the Internet to find out how autoradiography has been used in the study of ICT opportunity: Use of the Internet. translocation. Explain how the radioactive isotope carbon-14 (14C) has been used to investigate the pathway 14 of organic compounds from photosynthesis. Plants were exposed to C-labelled CO2 and some time later the plant organs (e.g. stem) were frozen, dehydrated and cut into thin sections. The sections were placed on a photographic film and developed. The position of any radioactively labelled substances would show up on the developed film. Provide students with a set of autoradiographs displaying the results of exposing plants to Source some photographs of autoradiographs 14 C-labelled CO2 and allowing them to photosynthesise for different time periods. Ask students from library or Internet. to work in pairs and discuss possible interpretations. Ask students to use the Internet to find out how aphids have been used in the study of ICT opportunity: Use of the Internet. translocation. Make sure students understand that aphids (e.g. greenfly) feed on plants by inserting their specialised mouthparts, called stylets, into the plant and probing until the tip of this structure penetrates a phloem sieve-tube member. Phloem sap flows into the aphid, force-feeding it as it swells to more than twice its size. While it is feeding the aphid can be anaesthetised and severed from its stylet so that the stylet continues to exude phloem sap for some hours, acting as a miniature tap. Ask students what the composition of phloem sap is. The phloem sap can be analysed to show its composition. The use of radioactive materials can also be combined with the aphid investigation to find out the rate of translocation of this material. Debate the ethics of using aphids in research on translocation.
408 | Qatar science scheme of work | Grade 12 advanced | Unit 12AB.2 | Biology 2 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
Explanations of translocation Ask students to use the Internet to find out what is meant by a source and a sink in ICT opportunity: Use of the Internet translocation. Make sure students understand that phloem sieve tubes carry sucrose from a sugar source (usually a leaf) to a sugar sink, an organ that either consumes sugar or stores it (e.g. growing roots, shoot tips and fruits). Ask students whether a particular organ can be both a source and a sink. Explain that, depending on the time of year, a storage organ, such as a tuber, bulb or tap root may act as either a source or a sink. Similarly, in spring a leaf can act as a sink during bud break (in woody perennials) or as a source (in herbaceous perennials). Ask students to use the Internet to find out what the competing explanations of translocation are ICT opportunity: Use of the Internet. and discuss the strength of the evidence for and against the claims. Make sure students understand that it is believed that the process of translocation occurs by a pressure flow or mass flow mechanism. This idea was first proposed by Ernst Munch in 1930. Exactly how this operates is subject to dispute. Make sure students understand that phloem sap transport has been measured at up to 1 m h–1 which is much too fast to be accounted for by either diffusion or cytoplasmic streaming alone. It has been calculated that the rate is about 10 000 times faster than it would be if substances were moving by diffusion rather than mass flow. Ask students to draw up a table comparing the different mechanisms of translocation. Ask students how loading and unloading of sucrose take place in the phloem. Make sure they understand that companion cells and phloem sieve elements work together. Sucrose is loaded into a companion cell by active transport at the source. This is usually a photosynthesising leaf. Some companion cells act as transfer cells. Energy as ATP is used to pump hydrogen ions out
of the companion cells before the hydrogen ions move back into the cell together with a sucrose molecule (co-transport) through the cell membrane, using a cell membrane carrier. This active process moves sucrose into the companion cell against the concentration gradient. The sucrose then moves through the plasmodesmata into the phloem sieve elements.
Make sure students understand that phloem loading results in a lowering of the water potential as the solute concentration is raised. Water flows into the phloem from the neighbouring xylem and other cells with a consequent rise in the pressure developed within the sieve tube. Sucrose is unloaded at the sink tissues that require sucrose, probably by diffusion. The removal of
sucrose results in a lowering of the water potential outside the sieve tubes as the solute
concentration is raised. Water flows out of the phloem and into the neighbouring xylem. Show students a diagram of Munch’s mass flow theory and ask them to explain the mass flow Prepare an OHT diagram of Munch’s mass flow of sucrose. theory.
Ask students to use the Internet to find out the limitations of the mass flow hypothesis and ICT opportunity: Use of the Internet. discover what alternative ideas have been put forward.
409 | Qatar science scheme of work | Grade 12 advanced | Unit 12AB.2 | Biology 2 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
In discussion with the class: • Point out that one as yet unanswered criticism of mass flow is that it cannot account for the observation that sugars and amino acids move at different rates in the phloem. • Say that a modified pressure flow or mass flow mechanism will probably be confirmed with more research discoveries. • Present students with an alternative theory – the electro-osmosis hypothesis, proposed in 1958 by Spanner. This is a modified mass flow theory involving the proposal that potassium ions are actively transported by companion cells across the sieve plate. This in turn draws the polarised water molecules across the plate. However, no consistent evidence for the existence of a potential difference across sieve plates has been demonstrated. • Make sure students understand the transcellular strand hypothesis suggested by Thaine in 1962. This proposed the presence of cytoplasmic strands passing through the sieve plates carrying out a form of cytoplasmic streaming. The active transport of solutes takes place within these strands. No consistent proof for the widespread presence of such strands has been demonstrated. Ask students to summarise their thoughts on translocation after reading all the evidence for the possible mechanisms. Discuss these with the class.
410 | Qatar science scheme of work | Grade 12 advanced | Unit 12AB.2 | Biology 2 © Education Institute 2005 Assessment Unit 12AB.2
Examples of assessment tasks and questions Notes School resources
Assessment Study the diagram of a capillary bed also including a lymphatic. Explain how tissue fluid is Provide students with a diagram of a capillary bed also including a lymphatic. Set up activities that allow formed and removed by reference to blood hydrostatic pressure and osmotic pressure. Also students to demonstrate what explain how lymph is produced. Compare the composition of the blood plasma, tissue fluid and they have learned in this unit. lymph. The activities can be provided Construct a pie chart to illustrate the composition of human blood. informally or formally during and at the end of the unit, or a. Explain the graph of the dissociation curve for haemoglobin. Provide students with a diagram of a
for homework. They can be b. Add a second curve to illustrate the dissociation that occurs at a higher carbon dioxide dissociation curve for haemoglobin. selected from the teaching concentration. Explain the shape you have drawn. activities or can be new
experiences. Choose tasks Complete the table to indicate which blood transfusions will be successful and which would and questions from the result in problems. Explain how the results apply to a patient of blood group A receiving a blood examples to incorporate in transfusion.
the activities. A B AB O
A
B
AB
O
Explain how wind speed affects the rate of transpiration of a leafy shoot.
Examine the photomicrograph of a cross-section of marram grass, Ammophilia arenaria, and Provide students with a photomicrograph of a identify and explain three xerophytic features that can be seen. cross-section of marram grass, Ammophilia arenaria.
Explain how the mass flow mechanism works by reference to the accompanying diagram. Provide students with a diagram of Munch’s mass flow theory.
Explain how aphids have helped provide evidence for the role of the phloem and the mechanism of translocation.
411 | Qatar science scheme of work | Grade 12 advanced | Unit 12AB.2 | Biology 2 © Education Institute 2005
412 | Qatar science scheme of work | Grade 12 advanced | Unit 12AB.2 | Biology 2 © Education Institute 2005 GRADE 12A: Biology 3 UNIT 12AB.3 18 hours Control, coordination and homeostasis
About this unit Previous learning Resources
This unit is the third of eight units on biology for To meet the expectations of this unit, students should already understand The main resources needed for this unit are: Grade 12 advanced. and be able to describe thermoregulation in humans and the roles of TRH • overhead projector (OHP) and various prepared transparencies (OHTs) The unit is designed to guide your planning and and TSH. They should be able to describe the similarities and differences • microscopes and slides of neurones and pancreas between nervous and hormonal control systems in mammals. They should teaching of biology lessons. It provides a link • models of brain, kidney and skin be able to explain the importance of homeostasis in mammals and describe between the standards for science and your • kidneys from butcher lesson plans. the process in terms of receptors, effectors and negative feedback. • video clips of nerve impulse action and temperature regulation The teaching and learning activities should help • tendon hammer you to plan the content and pace of lessons. Expectations • sets of various prepared cards (e.g. on temperature regulation, synapse Adapt the ideas to meet your students’ needs. events) For consolidation activities, look at the scheme of By the end of the unit, students know the structure of the mammalian • seeds of sunflowers and oats work for Grade 11A. kidney and its role in dealing with water and metabolic waste. They understand how the body controls water balance and the function of ADH. • temperature sensors, datalogger You can also supplement the activities with They know about thermoreceptors in the hypothalamus and understand • Internet access appropriate tasks and exercises from your body thermoregulation. They know the causes and effects of heatstroke. school’s textbooks and other resources. They know the structure and function of neurones and how nerve impulses Introduce the unit to students by summarising are transmitted. They know the main structures and functions of the brain. Key vocabulary and technical terms what they will learn and how this builds on earlier They know the main endocrine glands of the human body and their Students should understand, use and spell correctly: work. Review the unit at the end, drawing out the functions. They understand how human blood glucose levels are controlled. • homeostasis main learning points, links to other work and real They know the roles of plant auxins, gibberellins and abscisic acid. world applications. • osmoregulation, filtration, tubular reabsorption, tubular secretion • themoregulation, heatstroke • sensory, motor and intermediate neurones • simple and conditioned reflexes • action potential, resting potential, depolarisation, hyperpolarisation • saltatory conduction, synapse, neurotransmitters, summation • cerebrum, cerebellum, medulla oblongata, hypothalamus. • autonomic nervous system • glucose regulation, insulin, glucagon, diabetes mellitus • auxin, gibberellin, abscisic acid • oat coleoptile • synergist, antagonist
413 | Qatar science scheme of work | Grade 12 advanced | Unit 12AB.3 | Biology 3 © Education Institute 2005 Objectives for the unit Unit 12AB.3
SUPPORTING STANDARDS CORE STANDARDS EXTENSION STANDARDS 18 hours Grade 12 standards
3 hours 12A.9.1 Describe the gross external and internal structure of the kidney and the detailed structure of the nephron and associated blood vessels. The kidney, osmoregulation and waste control 12A.9.2 Using water potential terminology, explain the functioning of the kidney in osmoregulation and in controlling metabolic wastes. 2 hours 12A.9.3 Explain the role of the pituitary gland, ADH and aldosterone in osmoregulation.
Thermoregulation 11A.9.3 Describe thermoregulation in 12A.9.4 Explain the role of thermoreceptors in the hypothalamus in thermoregulation and and heatstroke humans and the roles of TRH and describe some physiological and behavioural responses of mammals to hot and TSH. cold conditions.
4 hours 12A.9.5 Describe the symptoms of heatstroke and explain why it occurs and how it can Neurones, the be avoided.
nerve impulse and 12A.9.6 Describe, compare and contrast the structure and function of sensory, motor synapses and intermediate neurones and know where they are found.
12A.9.7 Explain the function and importance of a reflex arc and differentiate between a 2 hours simple reflex and a conditioned reflex. Sensory receptors, 12A.9.8 Explain: the nature of a nerve impulse and the way it is transmitted; resting simple and potential; membrane depolarisation and action potential; refractory period; the conditioned passage of sodium and potassium ions. reflexes 12A.9.9 Explain the operation of sensory receptors as energy transducers. 2 hours 12A.9.10 Describe the roles of synapses in the nervous system in determining the direction of nerve impulse transmission and in allowing interconnections of nerve The human brain pathways.
11A.9.5 Describe the similarities and 12A.9.11 Describe the main structures of the human brain – cerebral hemispheres, 2 hours differences between nervous and cerebellum, medulla oblongata – and their functions. Know that the hypothalamus Endocrine glands hormonal control systems in mammals. is the link between the nervous and the endocrine control systems. and blood sugar 12A.9.12 Know the names, locations and functions of the main endocrine glands of humans. regulation 11A.9.2 Explain the importance of homeostasis 12A.9.13 Explain how insulin and glucagon control the blood glucose level and how failure 3 hours in mammals and describe the process of the system results in diabetes. in terms of receptors, effectors and The role of plant negative feedback. hormones 12A.10.1 Describe how auxins affect plant growth by cell extension, how abscisic acid prepares plants to withstand stress and how gibberellins cause effects such as internode extension, premature flowering and break dormancy.
414 | Qatar science scheme of work | Grade 12 advanced | Unit 12AB.3 | Biology 3 © Education Institute 2005 Activities Unit 12AB.3
Objectives Possible teaching activities Notes School resources
3 hours Reinforce previous knowledge on homeostasis with a quiz to focus on the kidney’s role in Recall Standard 11A.9.2 on homeostasis. Use this column to note the body. your own school’s The kidney, osmoregulation and resources, e.g. waste control Tell students to find out what role the kidney undertakes in homeostasis. They can find out ICT opportunity: Use of the Internet. from their textbook, library resources or the Internet. textbooks, worksheets. Describe the gross external and In this section you will need: a model kidney;
internal structure of the kidney and Introduce the anatomy of the kidney by showing students a model kidney. an OHT kidney diagram and copies for the detailed structure of the nephron Provide students with a kidney diagram showing its gross anatomy and ask them to label: labeling; animal kidneys from the butcher for and associated blood vessels. cortex, medulla, pyramid, pelvis, ureter, renal artery, renal vein. Show an OHT copy for dissection; an OHT diagram of a kidney and a Using water potential terminology, confirmation. nephron and copies for labeling; microscopes explain the functioning of the kidney Provide each pair of students with a real kidney obtained from the butcher. Ask them to and slides of kidney nephrons. in osmoregulation and in controlling examine it and then carefully dissect it by cutting a longitudinal section. Tell them to draw a Use OHT diagrams throughout the unit to metabolic wastes. diagram of the kidney and label the parts (e.g. cortex, medulla, pelvis). illustrate your explanations. Explain the role of the pituitary gland, Provide students with a kidney nephron diagram showing details of its structure. Ask them ADH and aldosterone in to label the diagram. Show an OHT and label such features as the Bowman’s capsule, osmoregulation. glomerulus, afferent arteriole and efferent arteriole blood vessels, proximal convoluted tubule, loop of Henle, peritubular capillary network, distal convoluted tubule and collecting duct. Allow students to examine microscope slides of the kidney nephrons to identify the various components. Ask students to make a presentation to the class to explain how the kidney osmoregulates ICT opportunity: Use of the Internet. and also how it gets rid of metabolic waste products. Explain the three main stages of kidney functioning to students: • glomerular filtration; • tubular reabsorption; • tubular secretion.
Examine each in turn.
Glomerular filtration Provide students with a series of statements about glomerular filtration that are deliberately Students should understand that this stage in the wrong sequence. Get students to arrange them in the correct order. For example: enables the body to recover those molecules • Small molecules and ions are filtered out into filtrate, and ions it cannot afford to lose. • Special cells on inside of the capsule, called podocytes • including nutrients such as glucose as well as waste such as urea. • allow filtering of blood at a rapid rate, • the wider afferent arteriole and narrower efferent arteriole • to prevent loss of plasma proteins from blood. • produces high blood pressure • The basement membrane acts, • create a high blood pressure in the glomerulus.
415 | Qatar science scheme of work | Grade 12 advanced | Unit 12AB.3 | Biology 3 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
Tubular reabsorption Provide students with a series of statements about tubular reabsorption that are Emphasise that the water molecules are deliberately in the wrong sequence. Get the students to arrange them in the correct order. reabsorbed passively by osmotic gradients For example: created by the active uptake and reabsorption of sodium ions. • The water potential of the fluid surrounding the tubule falls as the solute concentration rises • This stage allows the body to recover those molecules and ions it cannot afford to lose • Most of the water lost by filtration is reabsorbed here. • Selective reabsorption occurs • down the water potential gradient from the tubule • Sodium ions, Na+, are absorbed actively • In additional, the nutrients, such as glucose, amino acids and vitamins, are reabsorbed here • Water molecules are absorbed • Waste products remain in the tubule fluid and are not reabsorbed. • first in the proximal convoluted tubule, which causes chloride ions to be reabsorbed for maintaining electroneutrality.
Tubular secretion Provide students with a series of statements about tubular secretion that are deliberately in Students should understand that the the wrong sequence. Get the students to arrange them in the correct order. peritubular capillaries secrete certain For example: substances into the tubule fluid from the blood. • Nitrogenous waste products, such as ammonia, urea, uric acid and creatinine, are • Drugs that have been through the body are • Hydrogen ions are • secreted from the blood to the tubular fluid. • secreted to help maintain the blood pH. • actively secreted from the blood in the distal convoluted tubule.
416 | Qatar science scheme of work | Grade 12 advanced | Unit 12AB.3 | Biology 3 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
Give students a worksheet on osmoregulation to complete by filling in blank spaces. For example: ‘The majority of the water reabsorption takes place in the ______convoluted tubule; the regulation of the remaining water takes place in the loop of Henle and the ______duct. Tubular fluid leaving the proximal convoluted tubule is ______to the body fluids. The kidney has the ability to produce a strongly ______urine. The loop of Henle descends through an increasing ______gradient created by two solutes: salt (NaCl) and ______. The ascending limb of the loop loses Na+ and Cl– ions: ______at its base but ______from the upper portion of the loop. Urea ______out of the ______duct in the lower ______region, adding to the osmolality and ______the water ______of the tissue fluid at the inner medulla. Water is lost from the descending loop of the tubule down the water ______gradient. Fluid entering the ______convoluted tubule is still ______to the body fluids, since both ______and ______have been reabsorbed. It is when the fluid flows down through the ______duct that the remaining ______can be reabsorbed. As the fluid passes down the collecting duct through the ______it encounters the same increasing ______gradient as the descending loop. Water ______out of the collecting duct and into the renal medulla fluid, leaving the remaining tubular fluid becoming progressively ______to the blood plasma.’ Use a flow chart to develop students’ understanding of how ADH regulates the water balance of the body. Explain that water reabsorption is regulated by the combined activities of the hypothalamus, the pituitary gland, the antidiuretic hormone (ADH) and aldosterone. Make sure students understand the process of negative feedback regulation by ADH and aldosterone. After explaining the process, ask a few students to explain it again to the rest of the class. Make a set of cards showing the stages of the process of regulation by ADH and aldosterone. Mix up the cards and get students to rearrange them in the correct order.
Alternatively, make the ‘cards’ from pieces of OHT and invite a student to complete the exercise on the OHP in front of the class.
Show students a table comparing the composition of plasma and urine. Invite students to compare the values of the components (e.g. water, protein, glucose, urea, uric acid, ammonia, sodium ions, potassium ions, phosphate ions) and use the data to explain how the kidney contributes to homeostasis. Provide students with a diagram of the body and ask them to identify the location of the Provide a suitable diagram with the endocrine pituitary gland and other endocrine glands. positions to be identified.
417 | Qatar science scheme of work | Grade 12 advanced | Unit 12AB.3 | Biology 3 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
2 hours Devise experiments to investigate heat exchange in the human body, simulating the body Remind students of their work in physics on as a simple tin can. You can do these as a demonstration or ask students to carry them out the mechanisms of heat transfer if appropriate. Thermoregulation and heatstroke in pairs or groups. For example: This is a good cross-curricular activity. Explain the role of thermoreceptors • Fill a white can and a black can with cool water. Take their temperatures. Shine a strong These experiments could be used as project in the hypothalamus in light onto the cans. Take the temperature again and at regular intervals. Discuss the material to help students devise their own thermoregulation and describe some observations with students. experiments (e.g. using different coloured physiological and behavioural • Fill a white can and a black can with warm water. Take their temperatures. Take the ‘clothing’ on a can). responses of mammals to hot and temperature again and at regular intervals. Discuss the observations with students cold conditions. ICT opportunity: These heat exchange • Repeat the first experiment but add an ‘umbrella’/canopy (to simulate shade), either experiments (and others) could be conducted Describe the symptoms of white or black, between the light source and the cans. using temperature sensors and a datalogger heatstroke and explain why it occurs • Simulate the effects of tight and loose clothing by wrapping cloth tightly round one can to feed information into a computer for real- and how it can be avoided. and loosely round another identical can. Shine a bright light on each can and observe time on-line display and analysis.
any temperature changes. Discuss the observations with students. Discuss the four physical processes by which an organism exchanges heat with its environment: • conduction; • convection; • radiation; • evaporation. Provide a large diagram of a section of the skin and ask students to label features such as Prepare a suitable diagram and show students epidermis, dermis, capillaries, arteriole, vein, sweat pore, sweat duct, heat receptor, cold a model of the skin. receptor, hair, hair follicle, sebaceous gland, erector muscle. Use the diagram to help explain how the processes of heat exchange (conduction, convection, radiation and evaporation) are affected by the skin’s responses to: • over-heating; • over-cooling. Provide details of the ingenious experiment conducted by Benzinger on the role of the hypothalamus in temperature regulation. (Simultaneous measurements were made of the skin, the hypothalamus and the amount of heat lost. The subject lay in a large calorimeter at a temperature higher than body temperature and was asked to take iced drinks at regular intervals. The result showed that there was a perfect correlation between the temperature of the hypothalamus and the decrease in the rate of sweating.) Ask students to use their textbook to write an account of how the hypothalamus is involved in thermoregulation. Provide pairs of students with a set of cards, each with the name of one of the structures or Prepare suitable sets of cards. the stages of the control process for thermoregulation. Include the following: hypothalamus, thermoreceptors, heat gain centre, heat loss centre, increased sympathetic output, decreased sympathetic output, vasoconstriction, vasodilation. Ask students to organise the cards into a logical sequence on the desk to explain the actions of the hypothalamus in response to the body either over-heating or over-cooling. Prepare a similar set of thermoregulation control statements on OHT ‘cards’ and use them to demonstrate and consolidate the results from the class.
418 | Qatar science scheme of work | Grade 12 advanced | Unit 12AB.3 | Biology 3 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
Consolidate the students’ understanding of thermoregulation by asking them to explain the following phenomena.
• A swim on a hot day will cool the body. (The conduction of heat by water is up to 100
times that by air.)
• Wearing many layers of clothing is more likely to maintain body temperature than a single layer of the same thickness. (More air is trapped close to the skin and insulates the body.) • Loose-fitting garments are more comfortable than fitted garments outside in a warm climate like Qatar’s. (Air is a poor conductor of heat, so the air between the clothes and
the body prevents the body heating up as quickly from the heat of the Sun as it would without the air present.) • Hot humid climates are uncomfortable working conditions. (The high humidity reduces the evaporation of sweat and so cooling is less efficient.) • Moving into the shade where there is a light breeze and taking a cold drink cools the body. (Radiant heat energy is reduced, convection is increased by the breeze and heat
is conducted from the body to water in the intestinal tract – these all act to cool the body.) • Getting out of the sea on a cold day a swimmer shivers uncontrollably. (The involuntary contractions of muscle fibres generate heat quickly after the body’s hypothalamus has stimulated the voluntary nervous system to make the muscles contract in response to cooling of the blood.)
• A dog pants in warm conditions. (Dogs have no sweat glands on their hairy skin. Sweat glands are confined to pads on paws. Panting cools the dog by evaporation). • Although elephants are very large, they are able to keep cool. (Large ears act like radiators when the elephant is over-heated; behaviour includes bathing in a river and finding shade.) • Camels survive for days without water and are active in the full heat of the sun. (The
camel‘s tissues are extremely tolerant of dehydration. However, the camel also saves water by not sweating, at least until its body temperature reaches 40 °C. The camel’s body then loses an abnormal amount of heat at night, falling to around 34 °C. The following day the camel’s temperature climbs but doesn’t reach the upper lethal point because it starts from such a low point.)
• Mammals such as seals, whales and polar bears survive in very cold conditions. (Their bodies have adaptations to the cold, including extra insulation with adipose tissue and/or a thick fur coat with hairs raised.) Get students to record observations of domestic animals and keep a diary of how their behaviour changes in response to the weather conditions during a day and from day to day. Watch and discuss a video illustrating responses of mammals to hot and cold conditions. Give students the task of using the Internet to find out the symptoms of heatstroke and also ICT opportunity: Use of the Internet. establish why heatstroke occurs if someone stays out in the sun too long. Explain that the body can regulate its temperature between the upper and lower critical temperatures by physical mechanisms. However, above the upper critical temperature the body’s physical cooling mechanisms fail to keep the body’s temperature constant. The
419 | Qatar science scheme of work | Grade 12 advanced | Unit 12AB.3 | Biology 3 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
body‘s metabolic rate rises in response to the increased body temperature and, as a consequence, generates more heat. This results in a further rise in the metabolic rate, and so the body has entered an extremely dangerous cycle fuelled by positive feedback. This is where the change causes more change in the same direction. Prolonged exposure to excessively high environmental temperatures can result in the condition known as heatstroke. Discuss with the students why people acclimatised to living in high environmental temperatures frequently have a higher upper critical temperature.
Identify the symptoms affecting the brain, such as mental confusion, headaches, delirium, convulsions and unconsciousness, leading to death. In addition, body temperature is raised and the skin is hot and dry as a result of the sweating mechanism failing. Get students to produce a flow chart recording the stages in the development of heatstroke Enquiry skill 12A.3.4 and the symptoms of this medical emergency. Organise students into small groups to make a tourist guide to avoiding heatstroke.
4 hours Show students large unlabelled diagrams of sensory, motor and intermediate neurones. Prepare suitable diagrams. Get them to label, describe, compare and contrast the structure and function of these Neurones, the nerve impulse and neurones, using their textbook where necessary. synapses Organise students into pairs to produce posters with drawings of different neurones, using ICT opportunity: Use of the Internet. Describe, compare and contrast the library resources or the Internet. structure and function of sensory, motor and intermediate neurones Demonstrate neurone structure by using the microscope with a video camera attached. and know where they are found. Give students prepared microscope slides of neurones to examine. Students will need microscopes and prepared Explain the function and importance Provide a diagram of a cross-section of the spinal cord and get students to add the appropriate neurone slides. of a reflex arc and differentiate neurones for a reflex action (e.g. withdrawal reflex when touching a hot object with the hand). between a simple reflex and a Get students to find an appropriate passage in their textbook to read and then discuss to conditioned reflex. differentiate between a simple spinal reflex and a conditioned reflex. Explain: the nature of a nerve Get students to find, read and then discuss an appropriate passage in their textbook about impulse and the way it is transmitted; classical conditioning, as first demonstrated by the Russian physiologist Pavlov, who resting potential; membrane studied the production of saliva by dogs in response to food. depolarisation and action potential; Explain the nature of a nerve impulse and the way it is transmitted. Include details of Show an OHT of a nerve axon with the refractory period; the passage of resting potential, membrane depolarisation and action potential, refractory period, and the position of Na+ and K+ marked and use it to sodium and potassium ions. passage of sodium and potassium ions. illustrate stages of the explanation. Explain the operation of sensory Invite students, in turn, to describe one stage of a nerve impulse / action potential. Show an OHT of action potential to illustrate receptors as energy transducers. Ask all students to produce a flow chart of the generation and transmission of a nerve stages of the nerve impulse. Describe the roles of synapses in the impulse. nervous system in determining the direction of nerve impulse Watch and discuss a video on the transmission of nerve impulses. transmission and in allowing Provide pairs of students with a set of cards containing a series of statements about the Prepare suitable sets of cards. interconnections of nerve pathways. nature of a nerve impulse and the way it is transmitted, including: resting potential; membrane depolarisation and action potential; refractory period; the passage of sodium and potassium ions. Challenge students to arrange the cards in the correct order. This could be carried out as a competition for the quickest correct answer.
420 | Qatar science scheme of work | Grade 12 advanced | Unit 12AB.3 | Biology 3 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
Ask students to use their textbook find out about nerve impulses so that they can explain: • how the addition of myelin accelerates the transmission speed of the nerve impulse (explain saltatory conduction); • how the diameter of the axon affects speed of transmission of the nerve impulse.
Let students research the Internet to find out about and explain the operation of sensory ICT opportunity: Use of the Internet. receptors as energy transducers. (Specialised receptors are capable of transducing stimulus energy existing as electromagnetic (light), mechanical (sound, touch, pressure,
gravity), thermal (temperature change) and chemical (smell, taste) energy.) Ask students to make a chart of the sensory receptors in humans, including their location and the senses they detect. Let students investigate the interaction of different senses (e.g. taste, smell, sight and sound). Prepare a selection of mashed or evenly Working in small groups, get students to take it in turns to close their eyes and be given textured food samples. different food samples to taste and guess what they are eating. Alternatively, get students to pinch their nose and try to guess the particular flavour of a crisp they are given to taste. Provide samples of crisps of different flavours Ask students to use their textbook to find out the roles of synapses in the nervous system in determining the direction of nerve impulse transmission and in allowing interconnections of nerve pathways. Ensure students understand the role of synapses as follows: • Their primary role is to transmit information between neurones. • They pass impulses in one direction. Chemical neurotransmitter substance can only be released from one side of the synapse. This fact ensures that synapses act as one-way ‘gates’ in the nervous system, allowing impulses to pass in only one direction. • They act as junctions for a number of different neurones. Several synapses firing simultaneously may release sufficient neurotransmitter to stimulate the next neurone: this is spatial summation. Two or more impulses arriving in quick succession, called temporal summation, causes facilitation and stimulates the post-synaptic neurone. • Synapses can inhibit postsynaptic neurones. Inhibitory synapses release neurotransmitter substances which cause hyperpolarisation of the membrane, making it more difficult for an action potential to be generated. (Summation, as described above, from more excitatory synapses may overcome the effect of the inhibition.) Ask students to draw a diagram of a synapse and explain the mechanism of synaptic transmission in an excitatory synapse. Present students with a set of cards containing the steps of the mechanism of transmission Prepare a set of suitable cards. of a synapse in a random order so that, working in pairs, they can arrange them in the correct sequence. Arrange students in pairs or small groups to investigate the knee-jerk reflex. This simple Safety: Use a small tendon hammer and tap reflex demonstrates the response of the leg muscle to stretching the muscle spindle by the tendon lightly tapping the tendon lightly at a specific location. Get students to use their textbook to draw a diagram of the nervous pathways responsible for the knee-jerk reflex and explain the passage of the impulse from stimulus to response.
421 | Qatar science scheme of work | Grade 12 advanced | Unit 12AB.3 | Biology 3 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
2 hours Show students a model of the brain and the location of the main structures You will need a model of the brain, and an OHT of a suitable brain diagram, plus copies The human brain Provide a diagram of the brain and ask students to label the location of the main structures – cerebral hemispheres, cerebellum, medulla oblongata, hypothalamus. for students. Describe the main structures of the
human brain – cerebral Now get them to make a chart of the brain structures and their functions. hemispheres, cerebellum, medulla Present students with a set of cards containing details of the structures and functions of the Prepare suitable sets of cards. oblongata – and their functions. main parts of the human brain in a random order. Ask students, in pairs, to match them so Know that the hypothalamus is the the correct functions are with each structure. link between the nervous and the Get students write an account of the structure and function of the cerebral hemispheres, ICT opportunity: Use of the Internet. endocrine control systems. using the Internet, their textbook or library resources.
Make sure, in a later class discussion, that students have included and appreciate the following:
• The significance of the large size of the human cerebrum in relation to that of other
animals, and of the folds, or convolutions, that further increase its surface area. • The human cerebral cortex is composed of grey matter – the cell bodies of the neurones – and accounts for over 80% of the total brain mass. • The functions of the cerebrum are associated with the cerebral cortex: the outermost 3–5 mm layer. • Complex mental activities involved in intelligence, learning, thinking, sense of responsibility, reasoning and memory are associated with the cerebrum. • Sensory perception from many receptors in various locations of the body is fed to specific locations in the cerebral cortex. • The cerebral cortex is bilaterally symmetrical and is joined by the corpus callosum. • The surface of the cerebral cortex contains both sensory and motor areas involved in processing information. • Since the nerve fibres cross over in the medulla, the information to and from one side of the body is coordinated by the opposite side of the cerebral cortex. This means that the motor area of the right hemisphere of the cortex controls voluntary muscle movement on the left side of the body, and vice versa. • The size of the areas of the cortex representing different parts of the body is proportional to the extent of sensory innervation or complexity of movement. The hand, foot, tongue and lips are represented by large cortical areas. • Association areas in the cortex are, however, located in different hemispheres (e.g. speech, language and calculation are centred in the left hemisphere, while the right hemisphere controls artistic ability and spatial perception).
422 | Qatar science scheme of work | Grade 12 advanced | Unit 12AB.3 | Biology 3 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
Ask students to produce a map of the location of the major regions of the cerebral cortex and their functions. Tell them to write an account of the structure and function of the cerebellum. Make sure that in their account that they have included the following: • The cerebellum is part of the hindbrain, it is highly convoluted and it forms an outgrowth behind and beneath the cerebrum. • The primary function of the cerebellum is coordination of voluntary muscular movement, posture and balance. If one part of the body is moved, the cerebellum will coordinate other parts to ensure smooth action and balance. • The cerebellum appears to be involved in learning tasks, such as riding a bike or playing a musical instrument. Set students the task of using their textbook or library resources to write an account of the structure and function of the medulla oblongata. Check in discussion later that they have included the following: • The medulla oblongata controls breathing, heart rate and blood pressure. • Different groups of neurones are involved in the medulla for each of these functions. • Control of these functions is effected by impulses through the autonomic nervous system to the diaphragm, intercostal muscles, heart, and small arteries and arterioles. • The medulla contains sensory receptors for excess carbon dioxide. Set students the task of using their textbook or library resources to write an account of the function of the hypothalamus. Confirm that the following points have been addressed: • The hypothalamus is situated immediately above the pituitary gland. • The hypothalamus is linked directly to the posterior lobe of the pituitary by nerve fibres and to the anterior lobe by a complex of blood vessels. • Through these connections, the hypothalamus controls the output of hormones from both pituitary lobes. • The hypothalamus is the link between the nervous and the endocrine control systems. • In addition, the hypothalamus is involved in the control of: the autonomic nervous system, appetite, thirst and water balance, body temperature, emotional reactions (e.g. pleasure, rage and fear), sexual behaviour (including mating and child rearing), biological clocks (e.g. sleeping and waking), body temperature and secretion of some hormones.
423 | Qatar science scheme of work | Grade 12 advanced | Unit 12AB.3 | Biology 3 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
2 hours Provide each student with a large outline of the body and ask them to mark the locations of the main endocrine glands and the hormones they produce. Endocrine glands and blood sugar regulation Make sets of cards with the names of glands, the names of hormones and the functions of Prepare suitable sets of cards. hormones. Mix them up and ask students, working in pairs, to match them correctly. Know the names, locations and functions of the main endocrine Let students examine microscope slides of the pancreas displaying the islets of Students will need microscopes and prepared glands of humans. Langerhans. Use the microscope and video camera attachment to demonstrate the slides’ pancreas slides. details to students. Explain how insulin and glucagon control the blood glucose level and Tell students to use information from their textbook to explain how insulin and glucagon how failure of the system results in control the blood glucose level. diabetes. Show students a prepared OHT scheme of the control process and discuss. Prepare a suitable OHT. Ensure students appreciate that the conversion of glucose to glycogen inside cells is a way of storing carbohydrate without affecting the osmotic equilibrium. Also clarify that the glucose stored in the liver can later be taken out of the liver when blood sugar falls. However, the
glucose stored as glycogen in the skeletal muscles is not affected by glucagons.
Ask students to construct a flow chart diagram to illustrate the control of blood sugar levels.
Tell students to use information from their textbook or the library to explain what happens in diabetes mellitus. If someone in the class or school is diabetic, ask them (in confidence) if they would be willing to describe how the condition is controlled. Alternatively, ask someone who is diabetic to visit and talk to the class.
3 hours Explain to students how auxins affect plant growth by cell extension. Consolidate their knowledge of auxins by inviting individuals to explain the action of auxin to the rest of the The role of plant hormones class. Describe how auxins affect plant Use sunflower seedlings, about 10 cm tall, in investigations with exogenously applied auxin. Grow sunflower seedlings for 7–10 days in growth by cell extension, how Sunflowers are useful because they germinate and grow very quickly – from seed to 10 cm advance. abscisic acid prepares plants to seedling within 10 days. Let students work in pairs and devise their own experiments along withstand stress and how Warm (40 °C) lanolin spreads more easily. the following lines. Selected plants could either be left intact or have their stem tips gibberellins cause effects such as Enquiry skills 12A.1.2, 12A.1.3, 12A.1.5, removed before adding auxin (IAA) in lanolin to one side of the stem or all round. They internode extension, premature 12A.3.1–12A.3.3 should measure the degree of bending and growth of the stem and compare treated plants flowering and break dormancy. with intact control plants. They should also replicate the treatments. Discuss the results in class later. Grow oat seedlings and get students, in pairs, to use the coleoptiles to repeat the classic Grow oat seedlings for 4–7 days in advance. experiment by Went. Decapitate several coleoptiles, place them for an hour on an agar gel. Enquiry skills 12A.1.2, 12A.1.3, 12A.3.1– Cut a small piece of the gel. Decapitate a fresh coleoptile. Place a small cube of the gel on 12A.3.3 the tip eccentrically. Decapitate a second coleoptile and leave it untreated as a control. Show an OHT of the experimental results from Boysen-Jensen’s and Went’s classic Source details of Boysen-Jensen’s and Went’s phototropism experiments. Discuss the observations with students. classic phototropism experiments and prepare Invite individual students to explain to the class Boysen-Jensen’s and Went’s classic an OHT. phototropism experiments showing the effect of unilateral light on the distribution of auxin in a coleoptile. Ensure students appreciate that the growth response is caused by the stimulation of growth on the side furthest from the light by the redistributed auxin.
424 | Qatar science scheme of work | Grade 12 advanced | Unit 12AB.3 | Biology 3 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
Show students a graph of the effect of auxin concentration on the growth responses of Source a graph of the effect of auxin roots and shoots and discuss it with them. Make sure students understand that relatively concentration on the growth responses of
low auxin concentrations stimulate root growth and higher concentrations are required to roots and shoots. stimulate shoot growth; the concentrations that stimulate shoot growth inhibit root growth. Students can use their textbook, library resources or the Internet to find out about the ICT opportunity: Use of the Internet. commercial applications of auxins. They should discover references to: helping fruit set, promoting the rooting of cuttings as rooting hormones, and acting as selective weedkillers. Get students to use their textbook, library resources or the Internet to find out how Plant hormone or growth regulator effects are gibberellins cause effects such as internode extension, premature flowering and break not clearly understood and many of the effects dormancy. Discuss their findings in class. are due to several growth regulators Establish that: interacting. Growth regulators act both as synergists and antagonists in plants. • gibberellin needs auxin to cause effects on stem elongation; • auxin and gibberellin work synergistically to produce a greater effect together; • dwarf varieties (e.g. peas) can grow to normal height if treated with gibberellins; • a surge of gibberellin causes the plant to switch to reproductive growth and causes rapid elongation of stems in bolting (the growth of a floral stalk); • fruit development is promoted when both auxin and gibberellin work together; • seeds often contain high concentrations of gibberellins and, when seeds imbibe water, gibberellins are released from the seed embryo to break dormancy and promote germination; • gibberellin also functions to break dormancy in the resumption of growth by apical buds in spring; • in both seed dormancy and bud dormancy, gibberellin acts antagonistically to another hormone, abscisic acid, which generally inhibits plant growth. Tell students to use information from their textbook and the library to describe how abscisic acid affects plant growth. Discuss their findings in class. Ensure that the following points about abscisic acid are covered in students’ descriptions or during the class discussion: • it tends to slow down growth and to promote the dormant state (i.e. it is often antagonistic to auxin action); • it acts as a growth inhibitor and helps prepare the plant for winter by suspending both primary and secondary growth, and is also associated with maintaining dormancy of seeds; • it enables plants to cope with adverse conditions, acting as a ‘stress’ hormone (e.g. abscisic acid accumulates in leaves when they wilt and causes stomata to close, reducing transpiration and further wilting). For extension work, suggest to students that they investigate the effect of ethylene, another plant hormone. Ethylene is unique as a hormone because it is gaseous. It is associated with fruit ripening and also ageing or senescence, including leaf abscission (with auxin).
425 | Qatar science scheme of work | Grade 12 advanced | Unit 12AB.3 | Biology 3 © Education Institute 2005 Assessment Unit 12AB.3
Examples of assessment tasks and questions Notes School resources
Assessment Study the accompanying table, which shows and compares the composition of urine and Provide a table comparing the composition of urine with plasma. Set up activities that allow plasma. Identify, with your reasons, at least three functions of the kidney that are indicated by students to demonstrate what the data in the table. they have learned in this unit. a. Explain how the skin helps to regulate the body temperature during vigorous physical activity. The activities can be provided b. Explain how the skin is controlled in the responses described in (a) above. informally or formally during and at the end of the unit, or Draw a diagram of the nervous pathways responsible for the knee-jerk reflex and to explain the for homework. They can be passage of the impulse from stimulus to response. selected from the teaching
activities or can be new Explain how human blood sugar is regulated. experiences. Choose tasks Describe the passage of a nerve impulse across a synapse. and questions from the examples to incorporate in Explain why and how a plant shows a phototropic response to a unidirectional light source. the activities.
426 | Qatar science scheme of work | Grade 12 advanced | Unit 12AB.3 | Biology 3 © Education Institute 2005 GRADE 12A: Biology 4 UNIT 12AB.4 12 hours Human immune system
About this unit Previous learning Resources
This unit is the fourth of seven units on biology To meet the expectations of this unit, students should already understand The main resources needed for this unit are: for Grade 12 advanced. and know that the body produces antibodies against antigens, and • overhead projector (OHP) The unit is designed to guide your planning and understand the causes and transmission of HIV/AIDS, its global significance • push-fit beads and problems of control. teaching of biology lessons. It provides a link • sterile nutrient agar plates, cultures of bacteria (e.g. E. coli)
between the standards for science and your • antibiotic discs lesson plans. Expectations • set of cards containing details of diseases The teaching and learning activities should help • Internet access By the end of the unit, students understand the production of antibodies you to plan the content and pace of lessons. by the body and their mechanism of action against antigens. They Adapt the ideas to meet your students’ needs. For consolidation activities, look at the scheme of distinguish between active and passive immunity and relate this to Key vocabulary and technical terms work for Grade 11A. vaccination. They know the significance of stem cells and monoclonal antibodies. They know the role of the immune system in an allergic Students should understand, use and spell correctly: You can also supplement the activities with response. They understand the action of antibiotics and why resistance • antibodies, antigens, antigen–antibody complex appropriate tasks and exercises from your develops. They know the causes of cholera, influenza, malaria and TB, and • competent B lymphocytes, competent T lymphocytes school’s textbooks and other resources. explain their transmission, control and significance. They outline the • cytotoxic cells, memory cells Introduce the unit to students by summarising mechanism of gene therapy. • pluripotent stem cells what they will learn and how this builds on earlier Students who progress further understand the action of the HIV virus in • monoclonal antibodies, hybridoma, ‘magic bullets’ work. Review the unit at the end, drawing out the more detail and its effect on the body’s immune system, including why AIDS main learning points, links to other work and real • allergies, active immunity, passive immunity develops. They will be able to follow future biotechnological developments in world applications. • vaccination, antibiotics the use of stem cells, monoclonal antibodies and gene therapy in the diagnosis, treatment and cure of human diseases such as cancer. • cholera, influenza, malaria, tuberculosis (TB) • gene therapy, cystic fibrosis (CF), severe combined immunodeficiency syndrome (SCID)
427 | Qatar science scheme of work | Grade 12 advanced | Unit 12AB.4 | Biology 4 © Education Institute 2005 Objectives for the unit Unit 12AB.4
SUPPORTING STANDARDS CORE STANDARDS EXTENSION STANDARDS 12 hours Grade 12 standards
2 hours 11A.12.2 Explain the action of antibodies 12A.11.1 Explain the production and action of human antibodies against antigens against antigens in the human and distinguish between the actions of B lymphocytes and T lymphocytes. Specific immune system. immunity: B lymphocytes and 12A.11.2 Explain the function of memory cells in long-term immunity. T lymphocytes 12A.11.3 Relate the molecular structure of antibodies to their function.
12A.11.4 Explain the importance to health care of the pluripotency of stem cells and 2 hours the culturing of monoclonal antibodies.
Stem cells and 12A.11.5 Describe the role of the immune system in allergies such as hay fever. monoclonal 12A.11.6 Distinguish between the actions of active and passive immunity and antibodies explain the role of vaccination in combating disease.
12A.11.7 Explain the role of antibiotics in health care and understand how 1 hour pathogenic bacteria can become resistant to a particular antibiotic that was Allergies once effective.
11A.12.1 Explain the causes and transmission 12A.11.8 Explain the causes, transmission, control and global significance of 2 hours mechanisms of HIV/AIDS, how its cholera, influenza, malaria and tuberculosis (TB). spread may be controlled and the Active and significance of the pandemic. passive immunity 12A.11.9 Explain gene therapy, with reference to examples such as cystic fibrosis, 2 hours and understand the possible benefits and hazards of such treatments. Antibiotics and bacterial resistance
2 hours Cholera, influenza, malaria and tuberculosis (TB)
1 hour Gene therapy
428 | Qatar science scheme of work | Grade 12 advanced | Unit 12AB.4 | Biology 4 © Education Institute 2005 Activities Unit 12AB.4
Objectives Possible teaching activities Notes School resources
2 hours Reinforce previous knowledge by giving students a quiz about the body’s immune system. Produce OHTs of the responses of Use this column to note B lymphocytes and T lymphocytes. your own school’s Specific immunity: B Draw one OHT diagram to show the stages that B lymphocytes progress through in response to resources, e.g. lymphocytes and T contact with a specific antigen. Explain the sequence of stages to students. Then ask students to write a report to explain the action of B lymphocytes in the body. textbooks, worksheets. lymphocytes Ensure students appreciate that only competent B lymphocytes progress to produce a clone Explain the production and action of human antibodies and plasma cells. Plasma cells produce the specific antibodies to the antigen. This response is referred to as antibody-mediated immunity (or humoral immunity). against antigens and distinguish between the Draw another OHT diagram to show the stages that T lymphocytes progress through in actions of B lymphocytes and response to contact with a specific antigen. Explain the stages to students. Then ask students T lymphocytes. to write a report to explain the action of T lymphocytes in the body. Explain the function of Ensure students appreciate that competent T lymphocytes also produce a clone and, through memory cells in long-term T helper cells, assist the B lymphocytes in the production of plasma cells. Other T lymphocytes, immunity. including cytotoxic T cells, leave the lymph nodes to directly attack pathogens and body cells that have been invaded by viruses, for example, and destroy the infected cell. This response is Relate the molecular structure of antibodies to their therefore referred to as cell-mediated immunity. function. Ask students to explain the role of lymphocytes in the processes of antibody-mediated immunity ICT opportunity: Use of the Internet. and cell-mediated immunity using information from their textbooks, the library, or the Internet.
Ask students, individually, to produce a poster displaying the action of lymphocytes in immunity. Enquiry skill 12A.3.4 Ask students, individually, to produce a table comparing the activity of B and T lymphocytes. Make a list of statements about immunity and then ask students to indicate whether the statement applies to either B or T lymphocytes or to both. Ask students to explain why people normally only suffer once from some diseases ICT opportunity: Use of the Internet. (e.g. measles or mumps), yet they may suffer from many colds and several bouts of influenza in their lifetime. Let them find the answer from their textbooks, the library or the Internet. Get students to write, individually, a short article for a science magazine explaining the function of memory cells. Ask students to use the Internet to locate scientists who have done research on memory cells and find out about their contribution to our understanding. Show students an OHT diagram of an antibody and explain the structure of the components Enquiry skill 12A.3.4 that form the molecule. Show students a diagram of a 3D model antibody downloaded from the Internet. Produce a sheet with the antibody components separated and a list of the labels (heavy chains, light chains, constant region, variable chain, disulfide bonds, binding sites). Get students to cut out the components and stick them together to make an antibody and colour the parts appropriately. Tell students to write a report on the structure of the antibody molecule.
429 | Qatar science scheme of work | Grade 12 advanced | Unit 12AB.4 | Biology 4 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
Produce a sheet with a number of different antibody molecules (possibly four different-shaped Enquiry skills 12A.3.4 antigens and six of each type of antigen). Also, on the same sheet, show three copies of one specific antigen that will fit one of the antibodies only. Get students to cut out the shapes of the antibodies and antigens and use them to produce the antigen–antibody complex. Ensure students understand why antibodies are Y-shaped. They can then stick them on another sheet in the finished positions and colour them. Then tell students to write an explanation of their antibody reaction Ask students to build their own antibody molecule using push-fit beads of different colours. Provide push-fit beads of different colours. Recall the ABO blood group system and get students to explain which blood transfusions would be successful and which would not be successful. Ask students to use their textbooks, the library or the Internet to find out (and then write an ICT opportunity: Use of the Internet. explanation of) why transplanted organs are often rejected by their recipients.
2 hours Some time before studying this topic, get students to collect newspaper cuttings about stem cells. Discuss the contents of the cuttings. Stem cells and monoclonal antibodies Discuss the ethics of stem cell research with students. For example, it is a possibility that Enquiry skill 12A.2.2 individuals could soon produce clones of themselves. Reference to Aldous Huxley’s Brave New Explain the importance to World and eugenics could lead to a lively debate. health care of the pluripotency of stem cells and Ask students to produce a flow chart to show the potential of pluripotent stem cells in producing ICT opportunity: Use of the Internet. the culturing of monoclonal different body tissues. This may involve an Internet search. antibodies. Ask students to produce a magazine article about stem cells. Ask students to produce an article about the work of Georges Köhler and César Milstein on ICT opportunity: Use of the Internet and monoclonal antibodies. PowerPoint. Ask students to use the Internet to find out about the potential of monoclonal antibodies in the Enquiry skill 12A.3.4 diagnosis and in the treatment of diseases such as cancer. Discuss their findings in class. Get students to write a report or prepare a PowerPoint presentation on the role and future potential of monoclonal antibodies. Ask students why monoclonal antibodies have been called ‘magic bullets’. Ask students to produce a poster displaying the production of hybridomas and the action of monoclonal antibodies.
1 hour Conduct a class survey to find out how many students have allergies, what symptoms they display and how they are treated. Allergies Use large labelled diagrams on the board or OHP to explain the sequence of events that results Describe the role of the in the symptoms of an allergy such as hay fever. immune system in allergies such as hay fever. Ask students to produce a flow chart to explain the sequence of events that results in the symptoms of an allergy such as hay fever.
430 | Qatar science scheme of work | Grade 12 advanced | Unit 12AB.4 | Biology 4 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
2 hours As a revision exercise (see above) ask the students to explain why: • they normally only suffer once from a particular disease such as measles or mumps? Active and passive • they may suffer from many colds or from several bouts of influenza in their lifetime ? immunity ICT opportunity: Use of the Internet. Ask students to find out from their textbooks or the library why breastfeeding newborn babies is Distinguish between the an advantage to the baby’s survival in the first few weeks of life. actions of active and passive immunity and explain the role Ask students to find out from their textbooks, the library or the Internet why Edward Jenner is Enquiry skills 12A.2.1, 12A.2.5 of vaccination in combating such an important historical figure in immunity. Discuss his discovery of vaccination. disease. Conduct a class survey to find out whether any students have suffered from any specific The question of infectious diseases must be infectious diseases, and also which students have been vaccinated. Collate the data to produce handled sensitively if such matters are a class profile on immunity. confidential. Get students to find out which bacterial and viral diseases we can be immunised against by vaccination. Then draw up a table to display, in columns, the disease, the bacteria or virus name, the type of vaccine used (one from: killed pathogens, attenuated strain (of pathogens), or chemically modified toxins (toxoids)). New vaccines are also now being produced from genetically engineered microbes and monoclonal antibodies. Discuss why some people are not in favour of vaccinating their children. Enquiry skill 12A.2.2 Provide students with a graph showing the level of antibody in the blood after repeated injections with the same antigen. Ask them to explain the graph. Ask students to find out from their textbooks, the library or the Internet how it was possible for ICT opportunity: Use of the Internet. the World Health Organisation (WHO) to declare, in 1977, the eradication of smallpox. Act out a scenario in which a (pretend) venomous snake (e.g. a king cobra) comes into the Enquiry skill 12A.3.4 room and bites somebody. What can students do to save the person? (If not treated with anti- venom serum, they would die in less than two hours!) Get students to explain the sequence of events in the process of saving the patient. Discuss why passive immunity is so called, and why it confers only short-lived immunity. Ensure students appreciate that passive immunity involves using ‘borrowed’ antibodies, which, being proteins not produced by the individual, will be attacked as antigens by the body’s own antibodies.
431 | Qatar science scheme of work | Grade 12 advanced | Unit 12AB.4 | Biology 4 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
2 hours Ask students, in pairs, to investigate the effect of different antibiotics on the growth of a specific Safety: Ensure safe cultures of bacteria are bacteria using the following procedure. Heat a prepared tube of sterile nutrient agar until it melts sourced from educational suppliers. Make sure Antibiotics and bacterial and allow it to cool to hand hot. Inoculate the agar with a loop of E. coli and then pour it into a students operate the aseptic technique at all resistance sterile Petri plate. Allow the agar to solidify and then position small discs of filter paper times. Explain the role of antibiotics impregnated with antibiotic on the surface of the agar. Seal the dishes with two pieces of tape in health care and understand and incubate at 30 °C. Observe after 24 h to see if there are zones of inhibition of growth. Enquiry skill 12A.1.3 how pathogenic bacteria can Discuss the results as a class activity. See if the bacteria are unaffected by certain antibiotics become resistant to a and show different responses to other antibiotics. particular antibiotic that was Get students work in pairs, and ask each one to write a letter to a friend explaining one of: Enquiry skill 12A.3.4 once effective. • why an antibiotic once active against an illness-causing bacteria is no longer effective; • why the friend must take the complete course of prescribed antibiotics for an infection. Let them discuss their completed letters with their partners. Ask students to make a list of common antibiotics and the bacteria and illnesses they are effective against. Ask students to find out from the library why antibiotics are ineffective against viruses. Invite a hospital spokesperson to visit the class to discuss the problem of resistant bacteria in the health service. Tell students to write a report on this visit.
2 hours Arrange students into pairs and tell them to research two diseases each from cholera, influenza, ICT opportunity: Use of the Internet. malaria and tuberculosis (TB). Tell them each to write a report on their chosen disease, Cholera, influenza, malaria explaining its causes, transmission, control and global significance, and then to spend and tuberculosis (TB) 10 minutes peer-teaching one another. They should give their partner a copy of their report. Explain the causes, Get students to simulate the design of an experiment to test a new drug to protect against Enquiry skill 12A.1.3 transmission, control and malaria. global significance of cholera, influenza, malaria and Ask each student to produce a poster or information leaflet on one of the four illnesses: cholera, Enquiry skill 12A.3.4 tuberculosis (TB). influenza, malaria and tuberculosis (TB). Ask students to make a table comparing causes, transmission, control and global significance of the four illnesses. Provide pairs of students with a set of cards providing facts about cholera, influenza, malaria Provide each pair of students with a set of cards and tuberculosis (TB). Randomly shuffle the cards and then invite students to arrange the cards providing facts about cholera, influenza, malaria with the correct illness. This activity could be timed. and tuberculosis (TB). Provide WHO data about malaria and get students to use the data to draw maps of the Enquiry skills 12A.1.8, 12A.3.2 incidence of the disease. Provide students with WHO annual statistics on the incidence of cholera. Ask them to work as a Enquiry skill 12A.1.4 class to identify areas of the world with the greatest incidences and to try to account for peaks and troughs. Get students to write a leaflet for travellers giving advice on the avoidance of malaria. Enquiry skill 12A.3.4
432 | Qatar science scheme of work | Grade 12 advanced | Unit 12AB.4 | Biology 4 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
1 hour In advance of studying this topic, collect newspaper and magazine articles about gene therapy. Gene therapy Discuss the process of gene therapy using the collected newspaper articles. Explain the process using large labelled diagrams on the OHP. Explain gene therapy, with reference to examples such Arrange students into pairs, and tell each member of the pair to use the Internet to research a ICT opportunity: Use of Internet. as cystic fibrosis, and different example of gene therapy (e.g. cystic fibrosis (CF) and the much rarer severe combined Enquiry skills 12A.3.4 understand the possible immune deficiency (SCID)). Tell them each to write a report explaining the possible benefits and benefits and hazards of such hazards of such treatments, and then to spend 10 minutes peer-teaching one another. They treatments should give their partner a copy of their report. Ask students to draw a flow chart of the process of gene therapy for CF using viruses to insert Enquiry skills 12A.3.4 genes and using liposomes to insert genes. Ask each student to write a letter to an imaginary friend who suffers from CF to explain how the process works, and its possible benefits and hazards. Ask each student to produce a poster displaying gene therapy. Enquiry skills 12A.3.4
433 | Qatar science scheme of work | Grade 12 advanced | Unit 12AB.4 | Biology 4 © Education Institute 2005 Assessment Unit 12AB.4
Examples of assessment tasks and questions Notes School resources
Assessment Explain and compare the action of a B cell and a T cytotoxic cell on its respective target. Set up activities that allow students to demonstrate what Explain how long-term immunity is produced naturally by the body. they have learned in this unit. The activities can be provided informally or formally during Explain how a vaccination against an infectious disease confers immunity on an individual.
and at the end of the unit, or for homework. They can be Explain the difference between passive and active immunity. selected from the teaching activities or can be new experiences. Choose tasks Explain why monoclonal antibodies have been called ‘magic bullets’. and questions from the examples to incorporate in
the activities. Explain how the use of antibiotics has led to the phenomenon of bacterial resistance.
434 | Qatar science scheme of work | Grade 12 advanced | Unit 12AB.4 | Biology 4 © Education Institute 2005 GRADE 12A: Biology 5 UNIT 12AB.5 9 hours Genetic inheritance
About this unit Previous learning Resources
This unit is the fifth of seven units on biology for To meet the expectations of this unit, students should already understand The main resources needed for this unit are: Grade 12 advanced. that changes in DNA bases cause variation. They should know some • overhead projector (OHP) or whiteboard The unit is designed to guide your planning and causes of mutation. They should understand that a mutation causes a • corn (Zea mays) cobs change in DNA and that this can reduce the efficiency of, or block, an teaching of biology lessons. It provides a link • coloured beads enzyme. They should know the difference between genes and alleles and between the standards for science and your • chi-squared statistical tables lesson plans. that they are sections of DNA. They should understand how genetic variation occurs through the segregation of alleles and chromosome cross- • DNA autoradiograph from a genetic fingerprint The teaching and learning activities should help overs. They should understand how sex is determined in humans and the • Internet access you to plan the content and pace of lessons. mechanism of sex linkage. They should understand the difference between Adapt the ideas to meet your students’ needs. dominant and recessive alleles and be able to calculate genotype and For consolidation activities, look at the scheme of Key vocabulary and technical terms phenotype frequencies in monohybrid crosses. work for Grades 10A and 11A. Students should understand, use and spell correctly: You can also supplement the activities with • incomplete dominance, co-dominance appropriate tasks and exercises from your Expectations • dihybrid cross, Punnett square school’s textbooks and other resources. By the end of the unit, students calculate the frequency of different • chi-squared test Introduce the unit to students by summarising progeny from a cross with incomplete dominant alleles, from back crosses • Human Genome Project what they will learn and how this builds on earlier and from dihybrid crosses. They understand co-dominance and the • genetic fingerprinting, polymerase chain reaction (PCR) work. Review the unit at the end, drawing out the inheritance of phenotypic traits through multiple alleles. They use the chi- • genetic screening, amniocentesis, chorionic villus sampling main learning points, links to other work and real squared test to determine the significance of results of genetic crosses. world applications. They know about the Human Genome Project, genetic fingerprinting and • genetic counselling genetic screening and counselling. Students who progress further are able to follow and understand the principles of the technological advances and applications of the Human Genome Project, genetic fingerprinting and genetic screening and counselling.
435 | Qatar science scheme of work | Grade 12 advanced | Unit 12AB.5 | Biology 5 © Education Institute 2005 Objectives for the unit Unit 12AB.5
SUPPORTING STANDARDS CORE STANDARDS EXTENSION STANDARDS 9 hours Grade 12 standards
2 hours 11A.14.3 Explain the terms gene, allele, 12A.12.1 Calculate the ratios of the genotypes and phenotypes in the progeny of phenotype, genotype, dominant, incomplete dominant monohybrid crosses, dihybrid crosses (9:3:3:1 ratio) Calculating ratios recessive and co-dominant. and back crosses. of phenotypes and genotypes 11A.14.4 Use genetic diagrams to solve genetic problems involving monohybrid crosses. 1 hour 11A.14.5 Explain how variation occurs through Co-dominance segregation of alleles during gamete and multiple formation and through the crossing alleles over of chromosome segments during meiosis 1 hour 11A.14.6 Know how X and Y chromosomes 12A.12.2 Explain co-dominance and the inheritance of phenotypic traits such as determine sex in humans and the blood grouping through multiple alleles. Using the chi- inheritance pattern of sex-linked squared test characteristics.
12A.12.3 Use the chi-squared test to determine the significance of observed and 1 hour expected frequencies of different progeny in genetic crosses. The Human 12A.12.4 Know the purpose of the Human Genome Project. Genome Project
12A.12.5 Explain the basis of genetic fingerprinting and understand its advantages 2 hours and potential dangers.
Genetic 12A.12.6 Explain the basis of genetic screening for alleles of disadvantaging fingerprinting inherited conditions; understand the advantages and potential dangers of such screening and the need for genetic counselling. 2 hours Genetic screening
436 | Qatar science scheme of work | Grade 12 advanced | Unit 12AB.5 | Biology 5 © Education Institute 2005 Activities Unit 12AB.5
Objectives Possible teaching activities Notes School resources
2 hours Reinforce previous knowledge by giving students a quiz on genes, chromosomes, monohybrid Use this column to note crosses, genetic variation and sex-linked characteristics (from Unit 11AB.5). your own school’s Calculating ratios of resources, e.g. phenotypes and Tell students to use the library to read about, and make notes on, the work of Mendel and his Enquiry skill 12A.2.1 recording of experiments conducted on the garden pea. These experiments included textbooks, worksheets. genotypes monohybrid crosses, dihybrid crosses and back crosses. Calculate the ratios of the genotypes and phenotypes in Use large diagrams on the board or OHP to display examples of the phenotypes of pea plants involved in a variety of crosses. the progeny of incomplete dominant monohybrid Introduce an example of incomplete dominance (which Mendel did not meet). Show students crosses, dihybrid crosses large diagrams on the board or OHP to illustrate the typical cross between red and white
(9:3:3:1 ratio) and back snapdragon (Antirrhinum ) flowers. The F1 offspring are all pink. Ask students to explain this
crosses. observation. Ask them to predict what will happen in the F2 when the F1 plants are selfed. Confirm that when the pink plants are selfed, then a ratio of 1 red : 2 pink : 1 white is produced in Enquiry skill 12A.3.3 the F2. Ask students to explain the results using a Punnett square. Make sure students appreciate that the alleles remain discrete and that they do not blend together. Get students to predict the outcome of a back cross on the pink plants. Provide students with an example of a dihybrid cross. Use large diagrams on the board or OHP
showing the phenotypes of the parents and offspring for both F1 and F2. For example, use one of Mendel’s crosses in which he crossed plants with tall purple flowers Enquiry skill 12A.3.3
with plants with short white flowers, and produced all F1 tall purple flowers. These were selfed
and he finally obtained the following F2 plants: 96 tall purple, 31 tall white, 34 short purple and 11 short white flowers. Get students to explain the results using a Punnett square and work out the dihybrid ratio of 9:3:3:1. Provide students with a number of cobs of maize (Zea mays). Maize kernels display a number of easily recognisable characteristics, such as colour and shape. Ask to students to examine the kernels and make deductions about the genotypes of the parent plants. Use a computer simulation to investigate genetic crosses. ICT opportunity: Use of computer simulation. Get students to predict the outcomes of dihybrid crosses and compare their predictions with Enquiry skill 12A.1.2 collected data Simulate a dihybrid cross. Provide four bags, each containing the same number of a different colour of bead (e.g. 50 red beads in one bag, 50 blue in the second, 50 green in the third and 50 blue in the fourth). Arrange students in pairs and get each student to take two bags of the beads, pour them into one bag and mix thoroughly. Tell students to decide which colour will be the ‘dominant’ and which the ‘recessive’ allele. Each student then takes two beads out of their
bag and puts them together to represent the first of the dihybrid’s F2 progeny. This should be repeated at least 16 times and the ‘genotypes’ of the progeny identified. Ask students to compare their ratios with those of other pairs of students and discuss the results together.
437 | Qatar science scheme of work | Grade 12 advanced | Unit 12AB.5 | Biology 5 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
1 hour Distinguish co-dominance from incomplete dominance by asking students to find out, using the library, what the difference is between these genetic features. Co-dominance and multiple alleles Ensure students understand that, in co-dominance, both of the alleles are expressed in the phenotype, whereas, in incomplete dominance, the phenotype has an expression of a feature Explain co-dominance and some way between the phenotypes of the two parental varieties. the inheritance of phenotypic traits such as blood grouping A human example of co-dominance is in blood grouping. The three blood groups M, N and MN through multiple alleles. display the genotypes MM, NN, and MN, respectively. Note that MN is not intermediate between the M and N phenotypes, since both these factors are expressed on the membrane of a red blood cell. Explain multiple alleles by using the other example of human blood groups: the ABO system. Use the OHP or whiteboard to set up the examples and ask students to show the possible outcomes of parents with different blood groups producing children. Get a student to come to
the front of the class and explain their answer, by adding the details such as a Punnett square.
For example, ask them to explain how parents, one of blood group A and one of blood group B, can produce children with blood group A, B, AB or O.
1 hour Explain the purpose of the chi-squared test to students. It is a basic statistical test of experimental data that is used to indicate whether the observed data is significantly different Using the chi-squared test from the expected values. If a difference has been established, then the probability of this Use the chi-squared test to occurring by chance can be determined from statistical tables. determine the significance of Work through an example with students, using data from phenotypes resulting from a dihybrid observed and expected cross. Show them how to interpret the equation to calculate the chi-squared value. frequencies of different progeny in genetic crosses. Provide students with a worksheet containing results from a dihybrid cross displaying the Prepare worksheets on the appropriate dihybrid numbers of the progeny. Ask them to work out the chi-squared value to see if the difference crosses. between the observed and expected data is significant. They will need access to chi-squared Students will need access to chi-squared tables. tables. Enquiry skills 12A.3.3 Using other examples, get students to calculate the probability of obtaining the progeny of genetic crosses by chance.
1 hour Get students to visit the Human Genome Project website to gather information and to find out ICT opportunity: Use of the Internet. the purpose of this ambitious research project. The Human Genome Project The project is producing evidence of the sequence of the bases of the DNA in the entire human genome. Ask students how this knowledge will help people. Ensure they understand the huge Know the purpose of the potential benefits, for example: Human Genome Project. • health care – identification and mapping of the genes responsible for genetic diseases will help in the diagnosis, treatment and prevention of those conditions; • science – knowledge of the genome will give insight into the control of gene expression, cellular growth and differentiation; • evolutionary biology – enabling clarification of genetic relationships between species. Show students a video of the Human Genome Project. Get students to write an article for a magazine about the Human Genome Project.
438 | Qatar science scheme of work | Grade 12 advanced | Unit 12AB.5 | Biology 5 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
2 hours Before beginning this topic, get students to collect newspaper and magazine articles (e.g. New ICT opportunity: Newspaper and magazine Scientist) on genetic fingerprinting. Get them to use these and the Internet to find out about the articles can be obtained from the Internet. Genetic fingerprinting development of genetic fingerprinting by Alec Jeffreys and colleagues at the University of Enquiry skills 12A.2.1 Explain the basis of genetic Leicester, and to explain the principles of the procedure of genetic fingerprinting. Ask them to fingerprinting and understand produce a poster showing the main stages of genetic fingerprinting and its applications. its advantages and potential Examples of applications include: dangers. • settling paternity disputes; • settling disputes in hospitals where newborn babies have been accidentally switched; • revolutionising forensic work (using DNA extracted from cells in traces of blood, saliva, hair roots or, in rape cases, semen); • animal identification (e.g. establishing the variation of the whale population). Ask students to find out about the dangers or shortcomings of genetic fingerprinting, for example: • discovering that a child may not be the natural child of a parent may create problems for family relationships; • relatives show many similarities in their genetic fingerprints, so if more than one family member is a suspect of a crime, it may be difficult to be certain who is the culprit; • the use of the polymerase chain reaction (PCR) to amplify the amount of DNA for forensic work means the technique is now extremely sensitive to contamination; anyone who has shed dandruff or sneezed at the scene of a crime may become a suspect! Show students autoradiographs of genetic fingerprints of individuals from a murder case and ask them to select the possible suspect. Get students to write an article for a magazine about genetic fingerprints.
2 hours Ask students what they understand by the term genetic screening. Explain that everyone probably carries several genetic defects, and detecting the mutant genes in an individual is Genetic screening known as genetic screening. Explain the basis of genetic Ask students to find out from the library the situations in which genetic screening is particularly screening for alleles of relevant. These include: prenatal diagnosis, carrier diagnosis (e.g. CF, sickle cell), and disadvantaging inherited predictive diagnosis (e.g. Huntington’s disease). conditions; understand the advantages and potential Ask students to investigate and compare the advantages and dangers of prenatal diagnosis by Enquiry skills 12A.2.2 dangers of such screening amniocentesis and chorionic villus sampling. and the need for genetic Debate the ethics of genetic screening with students. Should the mother be able to choose to counselling. abort her foetus? Which genetic disorders should result in a foetus being aborted? Where do
you draw the line? Will we be able to breed genetic abnormalities out of the human race in the future? Ask students what they understand to be the role of a genetic counsellor. Ask students to find out whether their local hospital has a genetic counselling department and why only certain people may need to visit a genetic counsellor. Discuss the nature of a conversation that a counsellor might have with a husband and wife, one of whom thinks they are carrying an allele for a disadvantaging condition.
439 | Qatar science scheme of work | Grade 12 advanced | Unit 12AB.5 | Biology 5 © Education Institute 2005 Assessment Unit 12AB.5
Examples of assessment tasks and questions Notes School resources
Assessment Examine the kernels of cobs of maize (Zea mays). Make deductions about the genotypes of the Provide suitable cobs of maize for this question. Set up activities that allow parent plants. Justify and support your deductions by drawing diagrams to show the parental students to demonstrate what cross and a Punnett square to show the offspring. they have learned in this unit. Distinguish co-dominance from incomplete dominance by using examples. The activities can be provided informally or formally during Examine the worksheet containing results from a dihybrid cross and displaying the numbers of Provide a suitable worksheet and chi-squared
and at the end of the unit, or the progeny. Work out the chi-squared value to see if the difference between the observed and tables. for homework. They can be expected data is significant. selected from the teaching Write an article for a magazine about the Human Genome Project. activities or can be new experiences. Choose tasks Explain the principles of the procedure of genetic fingerprinting. and questions from the
examples to incorporate in Explain the advantages and dangers of genetic screening by prenatal diagnosis by the activities. amniocentesis and chorionic villus sampling.
440 | Qatar science scheme of work | Grade 12 advanced | Unit 12AB.5 | Biology 5 © Education Institute 2005 GRADE 12A: Biology 6 UNIT 12AB.6 13 hours Ecological relationships
About this unit Previous learning Resources
This unit is the sixth of seven units on biology for To meet the expectations of this unit, students should already understand The main resources needed for this unit are: Grade 12 advanced. that ecosystems are dynamic and subject to change, and that human • overhead projector(OHP) or whiteboard The unit is designed to guide your planning and activities can have an impact on the environment. • various sets of cards on the environment
teaching of biology lessons. It provides a link • datalogger/computer with sensors between the standards for science and your Expectations • haemocytometer lesson plans. • colorimeter By the end of the unit, students know how some organisms are The teaching and learning activities should help • fermenter, yeast culture you to plan the content and pace of lessons. structurally and physiologically adapted to their environment and distinguish between acclimatisation and adaptation. They understand the carrying • microscopes, video camera, still camera, monitor Adapt the ideas to meet your students’ needs. • video that illustrates biological control For consolidation activities, look at the scheme of capacity of a habitat and can use population curves. They understand work for Grade 11A. ecological colonisation and succession. They know examples of biological • Internet access control of unwanted organisms. They distinguish between environmental You can also supplement the activities with preservation and conservation and understand the conflicts between nature appropriate tasks and exercises from your conservation and production. Key vocabulary and technical terms school’s textbooks and other resources. Students who progress further will be able to follow and take part in future Students should understand, use and spell correctly: Introduce the unit to students by summarising debates on environmental issues such as nature conservation and food • environmental resistance, biotic factors, abiotic factors what they will learn and how this builds on earlier production. • biotic potential, carrying capacity work. Review the unit at the end, drawing out the main learning points, links to other work and real • ecological succession, primary colonisation, climax community world applications. • pioneer species, xerophyte, hydrophyte, mesophyte • sere, xerosere, hydrosere, zonation • biological control • environmental preservation, environmental conservation
441 | Qatar science scheme of work | Grade 12 advanced | Unit 12AB.6 | Biology 6 © Education Institute 2005 Objectives for the unit Unit 12AB.6
SUPPORTING STANDARDS CORE STANDARDS EXTENSION STANDARDS 13 hours Grade 12 standards
3 hours 12A.13.1 Explain examples of structural and physiological adaptations of animals to their environment. Animal adaptations and 12A.13.2 Distinguish between the permanent adaptation of an organism to its normal acclimatisation environment and the temporary acclimatisation of a visitor. 11A.16.1 Explain examples of a predator–prey 12A.14.1 Explain and give examples to illustrate the carrying capacity of an 2 hours relationship and the possible effects environment. on the population size of both the Dynamics of predator and the prey. population 11A.16.2 Explain examples of inter- and intra- growth specific competition for food and
space and the effects on the 2 hours distribution and size of the Ecological populations of organisms. succession 11A.16.3 Explain how disease affects the size 12A.14.2 Know how to construct and interpret population curves for different of population of organisms and the organisms; identify the stages in population growth and decline. significance of limiting factors in 2 hours determining the ultimate size of a Biological population. control 11A.16.4 Explain how the diversity and
numbers of organisms and the 2 hours environmental factors in an Comparing ecosystem form a dynamic preservation and relationship that is open to disruption. conservation 11A.16.5 Explain examples of short- and long- 12A.14.3 Describe the progression of the development of an ecological community term human impact on a variety of from primary colonisation to climax community. environments. 2 hours 12A.15.1 Explain examples of biological control of population growth in natural and Food production commercial settings. and conservation 12A.15.2 Assess the advantages and disadvantages of biological pest control.
12A.16.1 Explain the similarities and differences between environmental preservation and conservation; understand that conservation is a dynamic process involving management and reclamation.
12A.16.2 Explain how a wish to use an environment for food production can conflict with a wish for its conservation.
442 | Qatar science scheme of work | Grade 12 advanced | Unit 12AB.6 | Biology 6 © Education Institute 2005 Activities Unit 12AB.6
Objectives Possible teaching activities Notes School resources
3 hours Get students to do some card-matching activities. First provide a set of cards (set A) naming Prepare sets of appropriate cards. Use this column to note specific environments (e.g. ocean, polar, mountain, temperate, tropical savannah, desert, your own school’s Animal adaptations and steppe), and another set of cards (set B) describing the characteristics of the environments resources, e.g. acclimatisation (e.g. large expanse of grassland, large numbers of deciduous trees). Arrange students in pairs, textbooks, worksheets. Explain examples of mix up the cards and ask students to organise the cards into their matched groups. structural and physiological Next introduce a set of cards naming specific animals (set C), and another set of cards (set D) adaptations of animals to describing the adaptations of the animals (e.g. has layer of thick blubber, has extremely well- their environment. developed sense of smell / hearing / eyesight). Arrange students in pairs, mix up the cards and Distinguish between the ask students to organise the cards into their matched groups. permanent adaptation of an Alternatively, use these sets of cards for a class interactive activity. For example, issue each of Enquiry skill 12A.1.4 organism to its normal students several cards from set D and then ask another student to select an unseen card from set environment and the C. Ask the class to indicate who has got the specific animal adaptations on any of their cards. temporary acclimatisation of a visitor. Get students to work as a team to produce a booklet on the animals of Qatar. Give students lettered / numbered lists of animals, environments and adaptations in three columns Prepare suitable lists. and ask them to match the animal to the most appropriate components in the other columns. Give each student the name of a different animal, or ask them to name a species of their own ICT opportunity: Use of the Internet. choice, and then ask them to use the library or the Internet to find out how that animal is Enquiry skills 12A.1.6, 12A.1.8 adapted to its environment. Ask them each to write a short report on their animal and then make a brief presentation to the other students. Alternatively, ask each student to make a poster on the animal’s adaptations to its environment. Then hold a class poster conference in which students view each other’s work and ask each other questions. Take students on a field trip to a local ecosystem for study. For example, go to a local pond, a Visit opportunity: Visit a local ecosystem. rocky shore or an area of desert, and make observations of the plants and animals found there. Enquiry skills 12A.1.4, 12A.1.7 Ask students to make notes about how the organisms are adapted to the specific environment. Ensure students take appropriate measures to limit disturbance to wildlife and habitats when engaged in field work. Ask students to make a photographic record of the xerophytic adaptations of plants. ICT opportunity: Use of a digital camera. Distinguish between the permanent adaptation of an organism to its normal environment and the temporary acclimatisation of a visitor. Use the example of people who live permanently at altitude, such as the natives of Peru, compared with temporary visitors to the Andes. Show students graphs of the red blood cell counts of the two categories of people: those living permanently at altitude compared with visitors before, during and after their visit. Ask students to interpret the graphs using their textbook or the library. Ask students to find out from the library or the Internet the difficulties experienced by athletes at ICT opportunity: Use of the Internet. the Olympic Games and the football World Cup when they were held in Mexico. Enquiry skill 12A.1.8
443 | Qatar science scheme of work | Grade 12 advanced | Unit 12AB.6 | Biology 6 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
2 hours Reinforce previous knowledge of populations by quizzing students on inter- and intra-specific competition, disease and predator–prey relationships. Dynamics of population growth Get students to use computer models to explore population growth and decline. For example, ICT opportunity: Use of computer models. show how a change in an environmental factor, such as the introduction of a new predator, Explain and give examples to changes the carrying capacity of the population. illustrate the carrying capacity of an environment. Introduce the rapid growth rates of micro-organisms. Ask students to work out the potential numbers of micro-organisms produced from a bacteria with a doubling time of 20 minutes over Know how to construct and a period of 6, 12, 18 and 24 hours. Discuss the figures with the class. interpret population curves for different organisms; identify Provide students with a table of data for producing a growth curve for bacteria. Get them to plot Provide a suitable table of data. the stages in population a graph and to examine and explain shape obtained. Use this example to ask students to growth and decline. explain what the limits to growth are, and what an organism’s carrying capacity is. Ensure students appreciate that an organism growing in a limited environment experiences environmental resistance due to one or more limiting factors during growth. This means that biotic potential is not realised because of environmental changes (resistance), and the organism reaches its carrying capacity for a particular set of environmental factors. Either carry out the following activity as a demonstration or get students to work in pairs and You will need: fermenter, nutrient broth, yeast carry out these investigations, record the data and analyse it, and write a report. culture, datalogger, sensors, haemocytometer, Determine the growth pattern of a population of yeast cells by inoculating a liquid media, a colorimeter, video camera attached to a broth, in a laboratory fermenter, and follow the progress of growth. Use a datalogger and sensors microscope and monitor. to monitor the temperature, pH and oxygen level during the growth period. Remove unit samples ICT opportunity: Use of datalogger and at regular intervals. Several different methods can be used to follow the growth, including: sensors. • use a haemocytometer – the haemocytometer was originally used for counting blood cells, Details of the procedures can be found in but can be equally useful in counting yeast, bacteria or algae cells in liquid medium; P. Freeland, Micro-organisms in Action, Hodder & • use a colorimeter – a colorimeter can be used in a photometric method for estimating density Stoughton, 1991 (ISBN 0-340-53268-8). by recording the optical density of the sample. Demonstrate the use of the haemocytometer as a counting chamber for yeast cells by using a video camera attached to the microscope and displayed on a monitor. Get students to draw a diagram of the biotic factors (e.g. high reproductive rate, adequate food supply) and abiotic factors (e.g. light, temperature, oxygen supply) that influence a population’s carrying capacity. Ask students to suggest an example in the wild where the organism itself causes a reduction in its carrying capacity. Discuss their answers in class. One example is the African elephant, which has to be culled occasionally in game parks when its numbers exceed the carrying capacity, which causes the elephants to overgraze and destroy many of their food trees. Show students a graph of the change in the human population over time (or get them to Enquiry skill 12A.1.8 construct their own graph from census data) and some graphs showing how carrying capacity varies; debate which model may apply to the human population. Show students a growth curve of bacteria, yeast or a unicellular algae on an OHT. Ask them to explain the growth stages: the lag phase, the exponential or logarithmic phase, the stationary or plateau phase and the final decline or death phase.
444 | Qatar science scheme of work | Grade 12 advanced | Unit 12AB.6 | Biology 6 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
2 hours Discuss with students whether ecosystems are stable systems or whether they are changing dynamic systems. Ecological succession Introduce the concept of succession. Ensure students appreciate that populations of plants and Describe the progression of animals change over time through a succession of changes, or seres, to reach a relatively the development of an stable climax community. ecological community from primary colonisation to climax Take students to a suitable site displaying succession to carry out a field work investigation. For Visit opportunity: Visit a local site displaying community. example, visit an area that shows succession from open water to reed swamp to marsh land succession. and finally to dry land. Use a transect to follow the hydrosere from water to land. Alternatively, take students to follow a xerosere from the sand dunes at the shore back to woodland, if possible. A rocky shore tends to show zonation of seaweeds in the inter-tidal region rather than succession. However, small-scale succession can be seen by comparing different sites at different stages of development. In particular, when pieces of rock flake off, or boulders fall from cliffs or become overturned by stormy seas, these sites can be colonised by a succession of organisms and are suitable for study. Alternatively, a small area of rock can be scraped clear to investigate succession. Get students to use the library or the Internet to find information that helps them to draw a ICT opportunity: Use of the Internet. diagram of a primary succession. Ensure they include references to the following: pioneer Enquiry skill 12A.1.8 species, xerophytes, hydrophytes, xerosere, hydrosere, mesophytes, climax community.
Ask students to explain the process of primary succession: • for a xerosere; • for a hydrosere. Ask students to trace the development of a biological community through a photographic ICT opportunity: Use of a digital camera. record. Enquiry skill 12A.3.4
2 hours Discuss biological control with students. What is it? What is its aim? Biological control Ensure students appreciate that it involves humans exploiting a natural predator–prey relationship that exists between other species. A beneficial organism (the predator) is deployed Explain examples of against an undesirable one (the pest). The aim is not to eradicate the pest, but to reduce it to a biological control of level where it has little detrimental effect. population growth in natural and commercial settings. Show students a video that illustrates biological control. Assess the advantages and Ask students to use the library or the Internet to find examples of biological control in the natural ICT opportunity: Use of the Internet. disadvantages of biological environment and in the greenhouse. Examples they discover might include the following: pest control. • In the natural environment. There are two pests that lay their eggs on cattle dung in Australia: the bush fly and the buffalo fly. In addition, the dung carries the eggs of worms that parasitise the cattle. The indigenous dung beetles cannot deal with the soft cattle dung. The introduction of an African species of dung beetle, which buries the dung within 48 hours, has resulted in the control of the population of these pests. • In the greenhouse environment. Greenhouse whitefly are controlled by introducing a parasitic wasp into the greenhouse.
445 | Qatar science scheme of work | Grade 12 advanced | Unit 12AB.6 | Biology 6 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
Get students to match lists of examples of organisms involved in biological control. For example, have one list of the target organisms (the pests) and another list of the control agents (the predators). Additional lists could include harmful effects of the pest and method of action for the controlling agent. Carry out case studies of biological control, for example: • The cane toad. Ask students to use the library or the Internet to find out about the cane toad, ICT opportunity: Use of the Internet. which was introduced to Australia to control a sugar cane pest. The cane toad, a very large
amphibian, is now a cause of concern itself as it is eating its way through the local unique fauna. In addition, its skin is poisonous, so it is a danger to pets and potential predators. • The rabbit. Ask students to use the library or the Internet to find out about the control of the rabbit population in the UK. The controlling agent, a virus called myxomatosis, devastated the rabbit population, which had reached pest levels. Carry out a role-play exercise in which one student acts as an advocate for biological pest Enquiry skill 12A.3.4 control and another student acts as a protester against it.
2 hours Get students to make two lists – conservation and preservation – and ask them to write underneath the similarities and differences between these processes. Comparing preservation and conservation Alternatively, provide a list of statements referring to either conservation or preservation, or to Provide a suitable list. both, and get students to sort them into the appropriate categories. Explain the similarities and differences between Get students to contact environmental groups in Qatar and determine their policies regarding environmental preservation conservation and preservation. and conservation; understand Ask students to find out about National Parks and how they are managed. that conservation is a Carry out a simulation exercise. Divide the class into two and hold a debate. Get one side to Enquiry skill 12A.2.3 dynamic process involving present the case for a development and get the other side to present the case opposing it. For management and example: reclamation. • the proposed development of a new marina on an important wildlife site; • a proposed new highway development through an important nature reserve. Get students, in pairs, to use the library or the Internet to examine and compare old and new ICT opportunity: Use of the Internet. maps of an area of Qatar to see how land use has changed. Ask them what conclusions can be Enquiry skill 12A.2.3 drawn about the areas of nature reserves or wildlife sites over the last 30 years, for example.
Get students to find out which plant and animal species are in danger of extinction in the world and what measures, if any, are being taken to halt their decline.
446 | Qatar science scheme of work | Grade 12 advanced | Unit 12AB.6 | Biology 6 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
2 hours Debate the issue of growing genetically modified (GM) crops. Divide the class into two and ask ICT opportunity: Use of the Internet. one group to present the case for GM crops and the other group to present the case against, Food production and Enquiry skill 12A.2.3 citing the argument for conservation. Get them to use the library or Internet to find their conservation information. Explain how a wish to use an Ask students, individually, to review the evidence that science has provided the knowledge environment for food needed to breed plants and animals that could feed the world, and to consider why people production can conflict with a starve. wish for its conservation. Debate the issue of the deforestation that takes place to allow farmers to grow food crops. Divide the class into two groups and ask one group to support the policy and the other group to argue against the policy. Get them to use the library or Internet to find their information. Make sure students refer to the forest community as being essential to conserve the biodiversity of the planet and its genetic potential, and to the fact that it is an important potential source of new drugs, medicines and unknown, undiscovered chemicals. Debate the desirability of restricting fishing to conserve fish stocks. For example, use the case study of the cod. The NW Atlantic cod stocks were over-fished off the coast of Newfoundland by off-shore trawlers until the cod had virtually disappeared by 1992.They show little signs of any recovery and the fishermen are out of work. Conversely, the Norwegian government controlled fishing in the North Sea and the cod stocks are now recovering slowly. Introducing fishing quotas is not the best answer either. Many EU nations have fish quotas, but the fishermen just catch more fish than allowed in their quota, retain the higher value fish and throw back the rest (around a third of their catch) dead.
447 | Qatar science scheme of work | Grade 12 advanced | Unit 12AB.6 | Biology 6 © Education Institute 2005 Assessment Unit 12AB.6
Examples of assessment tasks and questions Notes School resources
Assessment a. Draw a population curve from the data provided for the growth of the micro-organism. Provide data for the growth of a micro-organism. Set up activities that allow b. Explain the four phases of growth identified. students to demonstrate what Explain, with examples, the relationship between an organism’s biotic potential, the they have learned in this unit. environment’s carrying capacity and the process of environmental resistance. The activities can be provided informally or formally during Describe the progression of the development of an ecological community from primary
and at the end of the unit, or colonisation to climax community. for homework. They can be selected from the teaching Explain, with examples, the advantages and disadvantages of biological pest control. activities or can be new Explain the similarities and differences between environmental preservation and conservation. experiences. Choose tasks and questions from the Explain the structural and physiological adaptations displayed by a named animal to its examples to incorporate in environment. the activities.
448 | Qatar science scheme of work | Grade 12 advanced | Unit 12AB.6 | Biology 6 © Education Institute 2005 GRADE 12A: Biology 7 UNIT 12AB.7 8 hours Biotechnology
About this unit Previous learning Resources
This unit is the seventh of seven units on biology To meet the expectations of this unit, students should already understand The main resources needed for this unit are: for Grade 12 advanced. and know how human blood glucose levels are controlled. They should • overhead projector (OHP), whiteboard The unit is designed to guide your planning and understand how micro-organisms and cells can be cultured. They should • video on human insulin manufacture understand the basic principles of genetic engineering. They should know teaching of biology lessons. It provides a link • glucose, glucose test strips between the standards for science and your the significance of stem cells and monoclonal antibodies. • lactase, catalase lesson plans. • Internet access The teaching and learning activities should help Expectations you to plan the content and pace of lessons. By the end of the unit, students understand how biosensors are used to Adapt the ideas to meet your students’ needs. Key vocabulary and technical terms monitor blood glucose levels in diabetes and how diabetes can be treated For consolidation activities, look at the scheme of Students should understand, use and spell correctly: work for Grade11A. with genetically produced insulin. They know some applications of monoclonal antibodies and immobilised enzymes. • biosensor, sensory agent, glucose oxidase You can also supplement the activities with • monoclonal antibodies, human chorionic gonadotrophin (HCG) appropriate tasks and exercises from your Students who progress further will be able to follow future developments • immobilised enzyme, catalase school’s textbooks and other resources. in the applications of biotechnology. In particular, they will be able to understand future developments in the applications of genetically • sodium alginate, carboxymethylcellulose Introduce the unit to students by summarising engineered organisms, biosensors, monoclonal antibodies and immobilised what they will learn and how this builds on earlier enzymes. work. Review the unit at the end, drawing out the main learning points, links to other work and real world applications.
449 | Qatar science scheme of work | Grade 12 advanced | Unit 12AB.7 | Biology 7 © Education Institute 2005 Objectives for the unit Unit 12AB.7
SUPPORTING STANDARDS CORE STANDARDS EXTENSION STANDARDS 8 hours Grade 12 standards
2 hours 11A.17.2 Know methods for the laboratory and 12A.17.1 Explain how genetically engineered human insulin was developed and is bulk culture of micro-organisms and now manufactured for use by diabetics. Genetic cell lines. engineering and insulin 11A.17.3 Explain the principles of gene cloning and the roles of restriction enzymes, recombinant DNA, plasmids and 2 hours bacteriophages. Biosensors and 12A.9.13 Explain how insulin and glucagon 12A.17.2 Explain what is meant by a biosensor. Know about the use of glucose diabetics control the blood glucose level and oxidase as a bio-recognition substance in biosensors used for monitoring
how failure of the system results in the blood glucose levels of diabetics. 2 hours diabetes.
Monoclonal 12A.11.3 Relate the molecular structure of 12A.17.3 Explain some biomedical uses of monoclonal antibodies in procedures antibodies in antibodies to their function. such as pregnancy testing. biomedicine 12A.11.4 Explain the importance to health care
of the pluripotency of stem cells and 2 hours the culturing of monoclonal Enzyme antibodies. immobilisation 12A.17.4 Explain the technique of enzyme immobilisation, understand the action advantages and disadvantages of the use of immobilised enzymes and describe some commercial applications.
450 | Qatar science scheme of work | Grade 12 advanced | Unit 12AB.7 | Biology 7 © Education Institute 2005 Activities Unit 12AB.7
Objectives Possible teaching activities Notes School resources
2 hours Reinforce previous knowledge by giving students a quiz on the principles of genetic Use this column to note engineering and also on the control of human blood glucose levels. your own school’s Genetic engineering and resources, e.g. insulin Ask students to use the library or the Internet to find out about, and write a report on, how ICT opportunity: Use of the Internet. genetically engineered human insulin was developed and is now manufactured for use by textbooks, worksheets. Explain how genetically diabetics. engineered human insulin was developed and is now Get students to identify the advantages of genetically engineered human insulin compared with manufactured for use by the traditional sources (traditional sources were animals and cadavers, where the problems of diabetics. supply, purity, immune response and disease, such as CJD, were risk factors). Get students to draw a flow chart to depict the commercial production of human insulin. Enquiry skill 12A.3.4 Show students a video on how genetically engineered human insulin was developed and is now manufactured for use by diabetics. Ask students to find out the number of diabetics in Qatar and the amount of insulin they require in a year. The Qatar National Health Authority may be able to supply this information. Get students to produce a poster displaying the production of human insulin using genetically Enquiry skill 12A.3.4 engineered E. coli.
2 hours Introduce the principle of a biosensor. Provide the class with three beakers of liquid: one Provide test strips for determination of glucose containing pure water, the others with a 1% and 2% solution of glucose, respectively, and ask in blood and urine for diabetics. Biosensors and diabetics students how they could tell which ones had glucose in solution. Testing with Benedict’s Explain what is meant by a solution may be suggested. Demonstrate the use of the dip-stick / test strip for glucose. Discuss biosensor. Know about the use the colour changes. See if students suggest the possibility of the involvement of an enzyme. of glucose oxidase as a bio- Ask students to find out how the glucose test strip works by using the library or the Internet. ICT opportunity: Use of the Internet. recognition substance in biosensors used for monitoring Ask students to share the information they found from the previous activity. Make sure they the blood glucose levels of appreciate that there are more complex biosensors that are capable of providing a continuous diabetics. read out of the quantitative levels of glucose. Ask students to find more details about these
biosensors. In particular, get them to find out the key components of a biosensor:
• artificial membrane (allows substrate through); • sensory agent (the immobilised enzyme glucose oxidase); • transducer (produces an electrical signal); • amplifier (increases size of signal); • display readout. Ask students to write and illustrate an account explaining the principle of how this biosensor works. They could produce a poster to accomplish this task. Invite a health professional (nurse or doctor) and/or a diabetic patient to come and talk to Opportunity for a health professional or students and answer questions about biosensors in the treatment of diabetes. diabetic patient visitor.
451 | Qatar science scheme of work | Grade 12 advanced | Unit 12AB.7 | Biology 7 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
Ask students to find out who makes biosensors. Organise members of the class to contact ICT opportunity: Use of the Internet. different organisations, or visit their websites, and ask for information about the operation of biosensors. Encourage students to find out about the other applications of biosensors, and to produce a table showing the different applications and what they use as the sensory agent and substrates. Alternatively, get students to match lists of biosensors and what they use as the sensory agent and substrates.
2 hours Reinforce previous knowledge on the production, action and structure of antibodies, the antibody–antigen complex formation and the culturing of monoclonal antibodies by giving Monoclonal antibodies in students a quiz. biomedicine Get students to use the Internet to determine the role of monoclonal antibodies in diagnostic ICT opportunity: Use of the Internet. Explain some biomedical uses of procedures such as pregnancy testing. monoclonal antibodies in procedures such as pregnancy Ask students to produce a flow chart of the role of monoclonal antibodies in pregnancy testing. Enquiry skill 12A.3.4 testing. Make sure they include the detection of human chorionic gonadotrophin (HCG) by the antibodies as the basis of the positive test.
Get students to use the Internet to investigate the wide application of monoclonal antibodies ICT opportunity: Use of the Internet. today and possible future uses. Uses in medical diagnosis and treatment include: • the diagnosis of cancer by identifying ‘tumour markers’; • the possibility of treatment using monoclonal antibodies as ‘magic bullets’ carrying drugs to specific cells; • blood typing; • detection of the rabies virus; • the possible production of a new vaccine against malaria; • kits to detect the presence of drugs in the urine of athletes.
2 hours Give students a worksheet describing a practical investigation involving the immobilised Prepare suitable worksheets for students. enzyme lactase and ask them to carry out the work in pairs. The enzyme is immobilised by Enzyme immobilisation action Details of the lactase experiment, along with entrapment in beads made of sodium alginate. The beads are packed into a column inside a information about other publications, can be Explain the technique of enzyme syringe barrel, and milk containing lactose is trickled through the column. Glucose and found on the National Centre for immobilisation, understand the galactose leave the column. Glucose is detected with a glucose test strip. Biotechnology Education website: advantages and disadvantages Give students a worksheet describing a practical investigation into the effect of the bead www.ncbe.reading.ac.uk of the use of immobilised diameter on the activity of the immobilised enzyme catalase and ask them to carry out the work enzymes and describe some Details of the catalase experiment can be in pairs. The size of the sodium alginate beads can be simply adjusted by changing the flow found in M. Roberts, T. King and M. Reiss, commercial applications. rate of the alginate / enzyme mixture into the calcium chloride solution. The rate of the reaction Practical Biology for Advanced Level, Nelson, by which the substrate hydrogen peroxide is broken down by catalase to release oxygen is 1994 (ISBN 0-17-448225-6). determined by the volume of oxygen collected over water. Enquiry skills 12A.1.1–12A.1.3 These enzyme investigations could be adapted and used for student projects.
452 | Qatar science scheme of work | Grade 12 advanced | Unit 12AB.7 | Biology 7 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
Ask students to explain the technique of enzyme immobilisation. Make sure they identify the three principal methods of immobilisation: • adsorption or physical binding (e.g. to glass beads); • entrapment (e.g. within a gelatinous polymer matrix of sodium alginate); • covalent bonding to carboxymethylcellulose. Encourage students to use the library or the Internet to find out about (and make lists of) the ICT opportunity: Use of the Internet. advantages and disadvantages of the use of immobilised enzymes. Get students to match lists of enzymes with the reactions catalysed and the commercial Prepare suitable lists of enzymes, the applications of the enzymes. reactions catalysed and the commercial Allocate an enzyme to each student and ask them to find out more details of its commercial applications. application. Tell each student to write a brief report on their enzyme and to present it to the class.
453 | Qatar science scheme of work | Grade 12 advanced | Unit 12AB.7 | Biology 7 © Education Institute 2005 Assessment Unit 12AB.7
Examples of assessment tasks and questions Notes School resources
Assessment Draw a flow chart to depict the commercial production of human insulin.
Set up activities that allow Explain the advantages of using genetically engineered human insulin compared with using the students to demonstrate what more traditional sources of insulin. they have learned in this unit. The activities can be provided a. Explain what is meant by a biosensor.
informally or formally during b. Explain the use of biosensors for diabetics. and at the end of the unit, or
for homework. They can be a. Explain the use of monoclonal antibodies in pregnancy testing. selected from the teaching b. Give five other examples of the use of monoclonal antibodies in the medical field. activities or can be new experiences. Choose tasks Provide a list of the reasons why immobilised enzymes are an advantage to a commercial and questions from the producer when compared with free enzymes in solutions. examples to incorporate in the activities.
454 | Qatar science scheme of work | Grade 12 advanced | Unit 12AB.7 | Biology 7 © Education Institute 2005 GRADE 12A: Chemistry 1 UNIT 12AC.1 17 hours The periodic table
About this unit Previous learning Resources This unit is the first of eight units on chemistry for The main resources needed for this unit are: To meet the expectations of this unit, students should already be able to Grade 12 advanced. recognise periodicity in the properties of elements and their compounds, • data and hint cards (for details see notes section in the activities) The unit is designed to guide your planning and with particular reference to elements of groups I, II, VII and VIII and the first • cards listing element symbols and electronegativity values teaching of chemistry lessons. It provides a link transition series. They should know a variety of processes by which useful • group I and II elements, pneumatic trough, pH paper between the standards for science and your substances are made from raw materials, including useful metals. They • video clips of caesium and rubidium reacting with water lesson plans. should know the properties of the common compounds of silicon and the • group I and II nitrates, carbonates and hydroxides The teaching and learning activities should help characteristic properties of the first-row transition elements. They should • class sets of equipment to heat solids and collect the gas evolved by you to plan the content and pace of lessons. know that transition metals are important redox reagents because they bubbling through limewater Adapt the ideas to meet your students’ needs. exhibit multiple oxidation states. • aqueous solutions of halogens, aqueous solutions of potassium (or
For consolidation activities, look at the scheme of sodium) halides, cyclohexane work for Grade 11A. Expectations • HCl, HBr, HI, gas jars You can also supplement the activities with By the end of the unit, students recognise the periodic variation in • solutions of potassium chloride, potassium bromide, potassium iodide, silver appropriate tasks and exercises from your ionisation energies, electron affinity and electronegativity, and predict nitrate solution, aqueous ammonia solution, halide solutions labelled A–E school’s textbooks and other resources. properties of elements from their position in the periodic table. They know • aqueous aluminium sulfate, dilute hydrochloric acid, dilute sodium hydroxide Introduce the unit to students by summarising the trends in the general properties of the s-, p- and d-block elements and • Internet access what they will learn and how this builds on earlier the specific properties and structures of some of their compounds. • strips of aluminium, copper(II) chloride , mercury(II) chloride work. Review the unit at the end, drawing out the Students who progress further recognise and understand the periodic • class sets of equipment to carry out electrolysis, aluminium strips, sulfuric main learning points, links to other work and real variation in ionisation energies, electron affinity and electronegativity, and acid, alizarin red (or other suitable dye) world applications. predict a vide variety properties of elements from their position in the • spreadsheet package periodic table. They know and understand the trends in the general • molecular models of diamond and silicon properties of the s-, p- and d-block elements and many specific properties • tin, lead, nitric acid, hydrochloric acid (dilute and concentrated), and structures of a wide range of their compounds. concentrated sodium hydroxide solution, potassium iodide • ammonium vanadate(V), zinc granules, acidified potassium manganate(VII), iron(II) ammonium sulfate, potassium iodide, sodium thiosulfate, sodium sulfite • mode-building kit • nickel(II) chloride, concentrated hydrochloric acid, sodium hydroxide
solution, Na2H2edta
Key vocabulary and technical terms Students should understand, use and spell correctly: • ionisation energy, electron affinity, electronegativity • thermal stability • amphiprotic, anodise • orbitals, redox, oxidising agents, reducing agents • ligand, complex, ligand exchange, coordinate bond, coordination number
455 | Qatar science scheme of work | Grade 12 advanced | Unit 12AC.1 | Chemistry 1 © Education Institute 2005 Standards for the unit Unit 12AC.1
SUPPORTING STANDARDS CORE STANDARDS EXTENSION STANDARDS 17 hours Grade 12 standards
3 hours 12A.19.1 Understand and use the term ionisation energy. Explain the factors influencing the ionisation energies of elements and the trends in Periodicity in ionisation energies across a period and down a group of the periodic properties table.
12A.19.2 Understand the terms electron affinity and electronegativity and recognise 4 hours and explain their periodic variation. s-block elements 10A.19.4 Describe trends in the physical and 12A.19.3 Know the general chemistry of the s-block elements, including:
chemical properties of the elements, • trends in the physical properties of the elements; 6 hours and their simple compounds, within • trends in the chemical properties of the elements; groups I, II, VII and VIII, and account p-block elements • general common properties of the compounds of the elements, for these trends in terms of electronic including the solubility, colour and thermal stability of the nitrates, structure. carbonates and hydroxides; 4 hours • the occurrence and extraction of the elements. d-block elements 12A.19.4 Outline and explain qualitatively the trends in the thermal stability of group II nitrates and carbonates and the variation in solubility of group II sulfates.
12A.19.5 Outline and explain trends in a number of properties down group VII: • physical properties; • the reactivity of the elements as oxidising agents; • the thermal stability of the hydride; • the reaction of the halide ions with silver nitrate followed by aqueous ammonia. 10.18.5 Explain, including the electrode 12A.19.6 Know how aluminium occurs and how it is extracted. Describe the main reactions, industrial electrolytic properties of aluminium, including: processes such as: … • the amphiprotic nature of the ion in its salts and solution; • the extraction of aluminium from • the suppression of the natural reactivity of the metal; molten aluminium oxide in • anodising. cryolite; … 12A.19.7 Explain how the small size and high charge of the aluminium ion leads to partial covalent bonding and its amphiprotic properties.
11.21.15 Compare and contrast the physical 12A.19.8 Outline and explain, in terms of structure and bonding, trends in a number and (inorganic) chemical properties of properties down group IV: of the group IV elements carbon and • melting point and electrical conductivity of the elements; silicon and their properties • the increased stability of the lower oxidation state; • the bonding, acid–base nature and thermal stability of the oxides; • the bonding in the chlorides, their volatility and their reaction with water.
456 | Qatar science scheme of work | Grade 12 advanced | Unit 12AC.1 | Chemistry 1 © Education Institute 2005 SUPPORTING STANDARDS CORE STANDARDS EXTENSION STANDARDS 17 hours Grade 12 standards
11.22.2 Know the electronic configurations 12A.19.9 Know that in transition metals, d-electrons can be involved in bonding as and the typical properties of the well as the outer s-electrons, resulting in multiple oxidation states. Predict first-row transition elements from its electronic configuration, the likely oxidation states of a transition element.
11.22.4 Know that transition metals can form one or more stable ions through the involvement of electrons from the inner (d) orbitals and know that this results in multiple oxidation states. . 12A.19.10 Explain how the variable oxidation states can result in transition metal ions acting as oxidising and reducing agents. Give examples of transition metal redox systems.
12A.19.11 Know that transition elements combine with ligands through dative bonding to form complexes and that these are often coloured. Give examples of ligand exchange reactions.
12A.19.12 Know that ligands in transition metal complexes may be neutral or anionic, and that the complexes usually exhibit four-fold (planar or tetrahedral) or six-fold (octahedral) coordination.
12A.19.13 Explain the formation of complexes in terms of coordinate bonds and the splitting of d-electron energy levels and know how this explains the colour of many transition metals’ complex ions.
11.22.3 State some common uses of some 12A.19.14 Know the biochemical importance of cobalt and iron. transition elements, including examples of catalysis by transition metals, and relate these uses to their properties
457 | Qatar science scheme of work | Grade 12 advanced | Unit 12AC.1 | Chemistry 1 © Education Institute 2005 Activities Unit 12AC.1
Objectives Possible teaching activities Notes School resources
3 hours Introduce the definition of ionisation energy to students and ask them to work individually to Use this column to note produce an equation of the type your own school’s Periodicity in properties M (g) → M+ + e– resources, e.g. Understand and use the term textbooks, worksheets. ionisation energy. Explain the Then give small groups of students data for the ionisation energies of a given period, group 1or Prepare sets of suitable data.
factors influencing the group 7. Ask each group to prepare a short presentation explaining the data they have been ionisation energies of given. Each group then pairs up with another group with a different set of data and peer teach elements and the trends in their interpretations. This process is repeated with a third group so all the data has been ionisation energies across a covered. period and down a group of Introduce the definition of electron affinity and electronegativity to students. Ask them, in small Prepare cards listing element symbols and the periodic table. groups, to list factors that will affect the electronegativity of an element. Give each group a set of electronegativity values. Understand the terms cards in two halves. One half has the symbols of elements and the other set has electron affinity and electronegativity values. Tell them to match the element to its electronegativity, giving reasons electronegativity and in each case. recognise and explain their Provide each group with a periodic table and ask them to predict the trends in electronegativity periodic variation. across a period. Ask them then to predict the periodic variation in electronegativities. Provide them with the appropriate data to check to see if their predictions are correct.
4 hours Allow students to view samples of lithium, sodium and potassium so that they can compare the Safety: Students should not handle sodium or s-block elements elements’ physical appearances at room temperature. Then ask them to research the Internet potassium. for data on other physical properties (e.g. melting points, boiling points, atomic radius, electron Know the general chemistry ICT opportunity: Use of the Internet. structure, principal oxidation number, electrical conductivity) in order to draw up a chart to of the s-block elements, compare and contrast the properties. including: Get students to repeat the process for the group II elements magnesium and calcium. • trends in the physical properties of the elements; Encourage students to use the data they have collected to draw comparisons between the two • trends in the chemical groups and find common patterns in the properties across the two groups. properties of the elements; Demonstrate the reactions of sodium and potassium with cold water in a pneumatic trough and Safety: Students should not handle sodium or • general common check the pH of the resultant solution. Allow students to react lithium, calcium and magnesium potassium. The reactions should be properties of the with cold water themselves and check the pH of the resultant solutions. Show video clips of the demonstrated using a pneumatic trough. compounds of the reactions of more reactive s-block metals with water. Show video clips of caesium and rubidium elements, including the Ask students to place samples of magnesium oxide, calcium oxide and barium oxide in water reacting with water. solubility, colour and and check the pH of the resultant solutions. Students will need pH paper. thermal stability of the Then ask them, in pairs, to produce a visual representation of any trends in reactivities. nitrates, carbonates and Enquiry skill 12.3.4 hydroxides; Provide samples of group I and II nitrates, carbonates and hydroxides for visual inspection. Tell Students will need appropriate equipment to students to record the visual features of these compounds. • the occurrence and heat solids and collect the gas evolved by extraction of the elements. bubbling through limewater. [continued]
458 | Qatar science scheme of work | Grade 12 advanced | Unit 12AC.1 | Chemistry 1 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
[continued] Ask students to heat samples of magnesium carbonate, calcium carbonate and barium Enquiry skill 12.4.1 Outline and explain carbonate, passing any gas evolved through limewater to test for carbon dioxide. From their qualitatively the trends in the observations they will be able to construct equations for the reactions and determine any trends thermal stability of group II in the thermal stability of the metal carbonates. nitrates and carbonates and Ask students to design a simple experiment to determine the relative solubilities of group I and II the variation in solubility of nitrates, carbonates and hydroxides then carry out their experiment. From this they can draw group II sulfates. out trends in solubilities. Give students data for the solubility of the group II sulfates at a given temperature. Ask them to Prepare hint cards. work in small groups to try to interpret why the solubility decreases on going down the group. Enquiry skills 12.1.1–12.1.4 You may like to produce ‘hint cards’ (e.g. one card might read ‘In order for a substance to dissolve, what are the energy changes involved?’) On completion of the task, ask groups to feed back their ideas to the whole group for class discussion.
Having established a trend of increasing thermal stability of the carbonates on going down Prepare hint cards. group II, ask students to work in small groups to discuss the findings and to explain why they occur. You may like to produce a series of ‘hint cards’ to help students who are struggling (e.g. one card might read ‘What is the charge density on a group II metal ion? What effect will this have on a negative ion near it?’). Once students have understood what is happening, ask them to predict (with reasons) what they think is the relative stability of group II nitrates. On completion of the task, ask groups to feed back their ideas to the whole group for class discussion. Give each student at random, the name of one of the group I or II elements. Then tell them to ICT opportunity: Use of the Internet. team up with anyone else in the class who has the same element and together use the Internet Enquiry skill 12.3.4 to research the occurrence and extraction of the element. Tell them to produce a summary sheet of notes for the rest of the class.
6 hours Allow students to view samples of chlorine, bromine and iodine so that they can compare the Safety: Chlorine must be kept in a sealed gas elements’ physical appearances at room temperature. Then ask them to research the Internet jar and bromine in a sealed container. Both p-block elements for data on other physical properties (e.g. melting points, boiling points, atomic radius, electron should be kept in a fume cupboard and only Outline and explain trends in structure, principal oxidation number, electrical conductivity) in order to draw up a chart to handled by a teacher. a number of properties down compare and contrast the properties. ICT opportunity: Use of the Internet. group VII: • physical properties; Show students the colours that form when aqueous solutions of chlorine, bromine and iodine are added to cyclohexane. • the reactivity of the elements as oxidising Provide students with aqueous solutions of chlorine, bromine and iodine, and solutions of Enquiry skills 12.3.1, 12.3.3 agents; potassium halides. Ask students to produce all the combinations of solutions of halogen • the thermal stability of the elements with solutions of halide salts and record their observations. In order to improve clarity, hydride; students may wish to add a few drops of cyclohexane to each mixture and record any colour changes to the organic layer. Tell students to use their observations to deduce a balanced • the reaction of the halide ions formula equation for each reaction occurring. They can then work in small discussion groups to with silver nitrate followed by produce ion equations for each reaction. Explain why these are redox reactions and encourage aqueous ammonia. students to deduce an order for the relative oxidising power of the halogens. [continued]
459 | Qatar science scheme of work | Grade 12 advanced | Unit 12AC.1 | Chemistry 1 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
[continued] Demonstrate what happens on heating hydrogen halides: no decomposition of HCl on heating; Safety: Carry out the demonstration in a fume Know how aluminium occurs brown fumes on heating HBr; copious violet fumes on plunging a heated glass rod into a gas jar cupboard. and how it is extracted. of HI. Ask students to research the bond lengths and bond enthalpies of the hydrogen halides Describe the main properties and plot these against atomic number. Then tell them to interpret the data and relate it to the of aluminium, including: observations of the practical demonstration. • the amphiprotic nature of Allow students to add silver nitrate solution to aqueous solutions of potassium chloride, the ion in its salts and potassium bromide and potassium iodide, and tell them to record the colours of the precipitates solution; formed. Then tell them to add aqueous ammonia solution to each precipitate and record their • the suppression of the observations. Students should be able to produce balanced equations for each reaction and natural reactivity of the write a method to test for the presence of chloride, bromide and iodide, respectively. Give the metal; class unknown samples of halide solutions labelled A–E and ask them to use the tests they • anodising. have just developed to determine which halide ion (if any) is present in each solution. Explain how the small size Use a revision quiz to remind students about the occurrence and extraction of aluminium from Prepare a suitable revision quiz. and high charge of the molten aluminium oxide in cryolite. aluminium ion leads to partial Encourage students to find out the meaning of amphiprotic. Ask them, individually, to measure Students will need an aqueous solution of covalent bonding and its the pH of an aqueous solution of aluminium sulfate. Then tell them to add alkali a drop at a time aluminium sulfate, dilute sodium hydroxide and amphiprotic properties. until a precipitate forms and then redissolves. They can then reverse the process by adding dilute hydrochloric acid. Outline and explain, in terms dilute acid a drop at a time. Provide students with a series of cards, each of which has a Enquiry skill 12.4.1 of structure and bonding, reactant, a product or arrows drawn on it. Tell students, in pairs, to arrange the cards to trends in a number of represent the reactions that have occurred. Once they have done this, they will be able to properties down group IV: identify how the aluminium salt in solution has behaved in an amphiprotic way. A class • melting point and electrical discussion can lead to an understanding of how the high charge density on the small aluminium conductivity of the ion leads to these reactions occurring. elements; Allow students to research the Internet for the uses for aluminium. Provide them with the ICT opportunity: Use of the Internet. • the increased stability of standard electrode potentials for aluminium and iron in order to pose the dilemma that Safety: Mercury(II) chloride is highly toxic by the lower oxidation state; aluminium reacts easily, yet for the uses it is put, to aluminium needs to have minimal corrosion. ingestion and skin absorption, so it must only be • the bonding, acid–base Ask students to observe and record what happens to strips of aluminium when they are: used by a teacher. nature and thermal stability (a) immersed in dilute sodium hydroxide solution; (b) immersed in dilute hydrochloric acid;
of the oxides; (c) left exposed to the air. Then tell students to treat aluminium strips with copper(II) chloride • the bonding in the solution and repeat the practical above. If you wish, you could, as a demonstration, treat chlorides, their volatility aluminium strips with mercury(II) chloride and repeat the practical. Both these treatments will and their reaction with allow students to see the difference in reactivity of clean aluminium compared with oxidised water. aluminium. Ask small groups of students to anodise aluminium (in the fume cupboard). The electrolyte used Students will need equipment to carry out can be 1 mol dm–3 sulfuric acid. After electrolysis, tell students to test the conductivity of the electrolysis, aluminium strips, sulfuric acid and anode and cathode. They could also try dyeing the anode and cathode with a solution of alizarin alizarin red (or other suitable dye). red, or some other suitable dye. Encourage them to discuss the advantages and applications of Enquiry skill 12.4.1 anodised aluminium.
460 | Qatar science scheme of work | Grade 12 advanced | Unit 12AC.1 | Chemistry 1 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
Ask students to investigate the trend from non-metallic to metallic on going down group IV of ICT opportunity: Use of the Internet and the periodic table. Ask them to research and plot graphs of the melting points, boiling points and suitable spreadsheet software to enter data in electrical conductivity of the group IV elements. Let them download images of the structures of order to plot graphs of melting points, boiling these elements and give them models of the giant structures of diamond and silicon to examine. points and electrical conductivity. Then ask them to work in small groups to explain how the properties they have researched are accounted for in terms of structure and bonding, and to present their ideas orally to the rest of the class. Give students a list of typical compounds of the group IV elements. This allows them to see the Students will need data relating to ionisation relative increase in frequency of the +2 oxidation state (as opposed to +4) on going down the energies and bond enthalpy data. group. Provide students with data relating to 1st, 2nd, 3rd and 4th ionisation energies for the group IV elements. Divide the class in half. Ask one half to draw a bar chart of 1st + 2nd IE values for each element and the other half to draw a bar chart of the 1st + 2nd + 3rd + 4th IE values for each element. This can lead to a whole class discussion on how the relative increase in the total energy needed to form Pb+4 compared with Sn+4 is so much greater than the relative increase in the total energy needed to form Pb+2 compared with Sn+2 To help students understand why carbon normally forms four covalent bonds, give them bond enthalpy data for Pb–Cl and C–Cl bonds and ask them to decide, on their own, what needs to happen to outer electrons in order for four bonds to be formed. Ask them to use the data you have provided to explain why it is energetically favourable for this to occur in carbon compounds but much less likely in lead compounds. Provide students with data referring to the melting points, boiling points and solubility in water ICT opportunity: Use of the Internet and Java for carbon dioxide, silicon(IV) oxide and lead(II) oxide. Then let them download 3D animations applets. (Java applets) of the structures of these compounds and use these to explain the differences in Safety: Concentrated acids and alkalis are properties. Encourage them to research the reactions of group IV oxides with acids and bases corrosive. The vapours are harmful to lungs, in order to establish that they become more basic in character on going down the group. eyes and skin. Concentrated nitric acid is an Ask students to prepare tin(IV) oxide and lead(IV) oxide by the action of concentrated nitric acid oxidising agent. Students must wear eye on each metal. Then tell them to heat the oxides they have synthesised and observe their protection, gloves and protective clothing, and reactions with dilute hydrochloric acid, concentrated hydrochloric acid, concentrated sodium carry out the activities in a fume cupboard. hydroxide and acidified potassium iodide. Ask them to write equations for what is occurring. Students will need: tin, lead, nitric acid, Ask students to research the thermal stability of the oxides and interpret any trends in terms of hydrochloric acid (dilute and concentrated), structure. concentrated sodium hydroxide solution, potassium iodide. Enquiry skills 12.4.1, 12.4.2
All group IV elements form chlorides of the formula type XCl4. Encourage students to build Students will need model-building kits. models of these compounds in order to explain their low boiling points. Tell them to look up the ICT opportunity: Use of the Internet. reactions of the chlorides with water and work in small discussion groups to explain why CCl4 Enquiry skill 12.3.4 does not react with water, yet SiCl4 is readily hydrolysed. They also need to consider why PbCl2 does not react with water. Ask them to make a poster display of their findings.
461 | Qatar science scheme of work | Grade 12 advanced | Unit 12AC.1 | Chemistry 1 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
4 hours Revisit the work done in Grade 11 relating to the fact that transition metals can form one or Students will need: data relating to standard more stable ions through the involvement of electrons from the inner (d) orbitals and that this electrode potentials, ammonium vanadate(V), d-block elements results in multiple oxidation states. Ask students to write out the electronic configurations for zinc granules, acidified potassium Know that in transition each of the first row transition metals. Taking into account the s3d and 4s electrons, ask them to manganate(VII), iron(II) ammonium sulfate, metals, d-electrons can be predict which ions they think would occur most readily and to check the literature to support this. potassium iodide, sodium thiosulfate, sodium involved in bonding as well as Provide students with standard electrode potential values for the reactions to follow. Ask them sulfite. the outer s-electrons, to reduce a solution of ammonium vanadate(V) to vanadium(II) using zinc granules, then Enquiry skill 12.3.4 resulting in multiple oxidation oxidise the vanadium(II) to vanadium(V) using acidified potassium manganate(VII), then work states. Predict from its out, using the electrode potential values. what reactions have occurred.. electronic configuration, the likely oxidation states of a Depending on time available and abilities of students, ask students to predict what they will transition element. observe when: + 2+ + - Explain how the variable • VO2 reacts with Fe , VO2 reacts with I (followed by the addition of thiosulfate); + oxidation states can result in • VO2 reacts with SO2 then has vanadium(II) added. transition metal ions acting as Then let them carry out these reactions, compare them with their predictions and complete half oxidising and reducing equations for the reactions occurring. agents. Give examples of Give students a series of diagrams and models of transition metal complexes. Ask them to Students will need diagrams and models of a transition metal redox make a list of the features that constitute a complex. You may wish to guide them in their wide range of complexes. systems. observations (e.g. ‘What do they all have in common?’, ‘What overall charge does the complex Know that transition elements carry?’, ‘What type of bonding is present?’, ‘What shape has the complex adopted?’). combine with ligands through Develop the terminology needed for this topic through class discussion of these ideas. dative bonding to form complexes and that these are Give students solid nickel(II) chloride and get them to make up an aqueous solution, add a few Students will need nickel(II) chloride, often coloured. Give drops of concentrated hydrochloric acid, dilute with water, add sodium hydroxide solution and concentrated hydrochloric acid, sodium examples of ligand exchange then add Na2H2edta. Tell them to record any colour change and write balanced equations for hydroxide solution, Na2H2edta. reactions. the reactions at each stage. Students might also investigate the formation of complexes Enquiry skills 12.4.1, 12.4.2 between a number of transition metal ions and the ligands ammonia and edta4–. Know that ligands in transition metal complexes Their findings will help them develop an understanding of ligand exchange. may be neutral or anionic, Divide the class into two and ask one half of students (working individually) to prepare a 5- ICT opportunity: Use of PowerPoint or similar and that the complexes minute lesson to explain the formation of complexes in terms of coordinate bonds and the package. usually exhibit four-fold splitting of d-electron energy levels. Ask the other half of the class (also working individually) to Enquiry skill 12.3.4. (planar or tetrahedral) or six- prepare a 5-minute lesson to explain how this brings about the colour of many transition metals’ fold (octahedral) coordination. complex ions. Tell all students to prepare some consolidation exercises on the topic Explain the formation of (e.g. crosswords, card-matching activities). When they have completed this, ask students to pair complexes in terms of up with someone in the opposite half of the class. Then tell each student to present their lesson, coordinate bonds and the possibly using PowerPoint or other presentation software, and ask their ‘pupil’ to complete the splitting of d-electron energy consolidation exercise. The roles are then reversed. levels and know how this Ask students to prepare a poster presentation for the class on the biochemical importance of ICT opportunity: Use of the Internet. explains the colour of many cobalt and iron. Enquiry skill 12.3.4 transition metals’ complex ions.
Know the biochemical importance of cobalt and iron.
462 | Qatar science scheme of work | Grade 12 advanced | Unit 12AC.1 | Chemistry 1 © Education Institute 2005 Assessment Unit 12AC.1
Examples of assessment tasks and questions Notes School resources
Assessment The halogens form a well-defined group of elements. Set up activities that allow Explain how the following support this statement: students to demonstrate what a. electron structure; they have learned in this unit. b. redox behaviour; The activities can be provided informally or formally during c. physical properties of the elements; and at the end of the unit, or d. thermal stability of the hydride. for homework. They can be
selected from the teaching Explain, giving examples why the elements in group IV become more metallic on going down activities or can be new the group. experiences. Choose tasks Complexes formed by edta4– involve pairs of electrons on nitrogen and oxygen atoms in the and questions from the same way as complexes formed by NH3 and H2O. Explain why stability constants of edta examples to incorporate in complexes in aqueous solution are generally so much larger than those of corresponding the activities. complexes with NH3 and H2O. From G. Burton, 2000, Salters Advanced Chemistry, Chemical Ideas, 2nd edn, Heinemann, p.273
Describe and account for the trends in thermal stabilities of the group II carbonates.
463 | Qatar science scheme of work | Grade 12 advanced | Unit 12AC.1 | Chemistry 1 © Education Institute 2005
464 | Qatar science scheme of work | Grade 12 advanced | Unit 12AC.1 | Chemistry 1 © Education Institute 2005 GRADE 12A: Chemistry 2 UNIT 12AC.2 10 hours Rates of reaction
About this unit Previous learning Resources
This unit is the second of eight units on To meet the expectations of this unit, students should already know the The main resources needed for this unit are: chemistry for Grade 12 advanced. factors that affect reaction rate and explain them in terms of the particle • numerical and graphical data (see ‘Notes’ column for details) The unit is designed to guide your planning and model. They should understand the concept of dynamic equilibrium. • potassium chromate(VI) solution 0.1 mol dm–3, dilute sulfuric acid
teaching of chemistry lessons. It provides a link 1.0 mol dm–3, sodium hydroxide solution 2.0 mol dm–3, potassium –3 –3 between the standards for science and your Expectations thyocyanate solution 0.5 mol dm , iron(III) chloride solution 0.5 mol dm , lesson plans. solid ammonium chloride –3 The teaching and learning activities should help By the end of the unit, students explain reaction rates in terms of particle • burettes, potassium iodide solution 1.00 mol dm , potassium –3 you to plan the content and pace of lessons. collisions and energy, and distinguish between first- and second-order peroxodisulfate(VI) solution 0.0400 mol dm , sodium thiosulfate solution reactions. They calculate the half-life of first-order reactions and understand –3 Adapt the ideas to meet your students’ needs. 0.0100 mol dm , freshly prepared starch solution, stopclocks For consolidation activities, look at the scheme of the relationship between rate constant and temperature. They deduce • water baths pre-set to a range of temperatures, sodium thiosulfate work for Grade 10A. mathematical expressions for equilibrium constants and use them in gas solution, hydrochloric acid, conical flasks, accurate thermometers, and solution reactions. You can also supplement the activities with waterproof crosses on card appropriate tasks and exercises from your Students who progress further explain reaction rates in terms of particle • Internet access school’s textbooks and other resources. collisions and energy, and distinguish between first- and second-order reactions with a mathematical appreciation of what is occurring. They Introduce the unit to students by summarising calculate the half-life of first-order reactions and understand mathematically Key vocabulary and technical terms what they will learn and how this builds on earlier the relationship between rate constant and temperature. They deduce work. Review the unit at the end, drawing out the Students should understand, use and spell correctly: mathematical expressions for complex equilibrium constants and use them main learning points, links to other work and real • rate of reaction, rate expression, rate constant, order of reaction, half-life in gas and solution reactions. world applications. • Arrhenius equation, activation energy, Boltzmann distribution • equilibrium, equilibrium constant, concentration, partial pressure, position of equilibrium
465 | Qatar science scheme of work | Grade 12 advanced | Unit 12AC.2 | Chemistry 2 © Education Institute 2005 Standards for the unit Unit 12AC.2
SUPPORTING STANDARDS CORE STANDARDS EXTENSION STANDARDS 10 hours Grade 12 standards
5 hours 10A.23.2 Know and measure the effect on 12A.20.1 Recognise that different reactions proceed at different rates and explain reaction rates of concentration, reaction rate in terms of particle collisions and particle energy. Order of reaction temperature and particle size, and
explain the effect in terms of a kinetic 3 hours particle model. Reaction rate and 10A.23.1 Know that reaction rates vary 12A.20.2 Derive and use rate expressions of the form rate = k[A]m[B]n from data and temperature considerably and be able to produce, draw and analyse graphical representations for zero, first- and second- and analyse graphically, data from order reactions in a specified reactant. rate experiments. 2 hours 10A.23.5 Know that many reactions occur in Equilibrium multiple steps and that only one constants determines the reaction rate.
10A.23.6 Explain a bimolecular reaction in 12A.20.3 Calculate the half-life of first-order reactions and show an understanding of terms of particle collisions and why it is concentration independent. recognise that the chance of a reaction depends on particle concentration and particle energy. 12A.20.4 Describe qualitatively the relationship between the rate constant and temperature. 12A.20.5 Use the Arrhenius equation to determine the energy of activation given values of the rate constant for different temperatures. 12A.20.6 Understand the Boltzmann distribution and demonstrate its importance in reaction kinetics, with particular reference to activation energy. 10A.23.7 Understand, in terms of rates of the 12A.20.7 Deduce expressions for forward and backward rate constants for a simple forward and reverse reactions, what bimolecular reaction and hence deduce expressions for equilibrium
is meant by a reversible reaction and constants in terms of concentrations (Kc) and partial pressures (Kp). dynamic equilibrium. 12A.20.8 Calculate the values of equilibrium constants in terms of concentrations or partial pressures from appropriate data, and calculate the quantities present at equilibrium, given appropriate data.
12A.20.9 Understand and use the term position of equilibrium as applied to a reversible reaction and know that the size of an equilibrium constant is an indication of the extent to which a reaction nears completion.
466 | Qatar science scheme of work | Grade 12 advanced | Unit 12AC.2 | Chemistry 2 © Education Institute 2005 Activities Unit 12AC.2
Objectives Possible teaching activities Notes School resources
5 hours Ask students to list as many everyday chemical reactions as they can and then place them in Use this column to note order of rate of reaction (e.g. dynamite exploding, iron bar rusting). Ask them to consider work your own school’s Order of reaction done in Grade 10 on reaction rates and use these ideas to relate the reaction rate to rate of resources, e.g. Recognise that different particle collision and particle energy. textbooks, worksheets. reactions proceed at different rates and explain reaction Provide students with numerical and graphical data for reactions that are zero, first and second Provide a range of data here. Class sets of equipment rate in terms of particle order with respect to particular reactants. Ask them, in small groups, to classify the data into Reagents needed: potassium iodide solution collisions and particle energy. zero, first and second order and use group discussion to decide what the characteristics of each 1.00 mol dm–3, potassium peroxodisulfate(VI) are. Go through the theory of rate equations and then ask students to derive the rate equations –3 Derive and use rate solution 0.0400 mol dm , sodium thiosulfate for each of the examples they have been provided with. Ask students to use a reaction (e.g. the solution 0.0100 mol dm–3, freshly prepared expressions of the form – 2– iodine clock reaction for the reaction of iodide ions (I ) with peroxodisulfate(VI) (S2O8 ) ions) to rate = k[A]m[B]n from data starch solution. design an investigation. Tell them to record how the rate of reaction varies as the concentration and draw and analyse Enquiry skills 12A.1.1, 12A.1.3–12A.1.5, of each reactant in is varied. From this they will be able to determine the rate equation and graphical representations for 12A.3.1–12A.3.3 derive the rate constant (including units). zero, first- and second-order reactions in a specified reactant. Provide numerical and graphical data of concentration versus time for first-order reactions. Ask Provide suitable numerical and graphical data. Calculate the half-life of first- every student in the class to calculate a value for t1/2 and share these with the class. This will order reactions and show an clearly demonstrate that this value does not vary with changing concentration. understanding of why it is concentration independent.
3 hours Ask students, in pairs, to carry out the reaction of sodium thiosulfate with dilute hydrochloric Students will need: water baths pre-set to a acid (stopping the reaction when a cross on a piece of paper under the reaction flask becomes range of temperatures, sodium thiosulfate Rate of reaction and obscured from view). Tell them that they need to keep the concentrations the same and vary solution 0.5 mol dm–3, hydrochloric acid temperature –3 the temperature at which the reaction occurs. Tell them to calculate k for each reaction and then 1 mol dm , conical flasks, accurate
Describe qualitatively the plot lnk versus 1/T (T is in K). The gradient (–EA/RT) will allow EA, the activation enthalpy, to be thermometers, waterproof crosses on card. relationship between the rate calculated. Enquiry skills 12A.3.1–12A.3.3, 12A.4.1, constant and temperature. 12A.4.2 Use the Arrhenius equation to Ask students to research the Boltzmann distribution on the Internet and to discuss, in small ICT opportunity: Use of the Internet. determine the energy of groups, the importance of this to reaction kinetics. Then tell them to use what they have activation given values of the discovered about the Boltzmann distribution to relate their findings about reaction rate and rate constant for different temperature to particle energy and activation energy. temperatures. Understand the Boltzmann distribution and demonstrate its importance in reaction kinetics, with particular reference to activation energy.
467 | Qatar science scheme of work | Grade 12 advanced | Unit 12AC.2 | Chemistry 2 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
2 hours Instruct students on how to derive the equilibrium constant in terms of concentration (Kc) for the Provide appropriate numerical data. Equilibrium constants reaction aA + bB → cC +dD Deduce expressions for forward and backward rate Give them a series of balanced equations and ask them to derive equations for Kc. Provide Enquiry skill 12A.1.8 constants for a simple students with some numerical data for reactions at equilibrium and ask them to calculate values bimolecular reaction and (and units) for the different Kc values. hence deduce expressions for equilibrium constants in Introduce students to the idea that the concentration of a gas in a gaseous mixture is Provide suitable examples of gaseous reactions proportional to its partial pressure. Allow them to practise calculating partial pressures. Ask and data to use to calculate Kp. terms of concentrations (Kc) them to consider how expressions for Kc are derived and use these ideas to develop the idea of and partial pressures (Kp). Kp. Take them through one example of how to derive and determine the value for Kp under Calculate the values of given conditions. Give students balanced equations for gaseous reactions and ask them to equilibrium constants in terms derive expressions for Kp. Provide them with a variety of data that allow them to develop their of concentrations or partial understanding of how to use data to derive partial pressures and numerical values for Kp. Ask pressures from appropriate students to form small groups and take it in turns to explain how they completed each example. data, and calculate the It may be appropriate to differentiate the examples given to each group. quantities present at equilibrium, given appropriate Ask students to carry out the following reversible reactions to demonstrate to them the idea of Reagents needed: potassium chromate(VI) –3 data. position of equilibrium. solution 0.1 mol dm , dilute sulfuric –3 (i) Fe3+ +SCN– ⇋ [FeSCN]2+ acid 1.0 mol dm , sodium hydroxide solution Understand and use the term 2.0 mol dm–3, potassium thyocyanate position of equilibrium as Using test-tube reactions allows students to observe how the addition of each reactant and the solution 0.5 mol dm–3, iron(III) chloride solution applied to a reversible product shifts the position of equilibrium –3 2– + 2– 0.5 mol dm , solid ammonium chloride reaction and know that the (ii) 2CrO4 +2H ⇋ Cr2O7 +H2O Enquiry skills 12A.4.1, 12A.4.2 size of an equilibrium Using test-tube reactions allows students observe how the addition of acid and alkali shifts the constant is an indication of position of equilibrium. the extent to which a reaction Provide students with actual values of K values for given reactions at different temperatures. nears completion. c Ask them to work in small groups to decide what this means in terms of the extent to which the
reaction has progressed (i.e the larger the value of Kc the greater the extent of the reaction).
468 | Qatar science scheme of work | Grade 12 advanced | Unit 12AC.2 | Chemistry 2 © Education Institute 2005 Assessment Unit 12AC.2
Examples of assessment tasks and questions Notes School resources
Assessment The results of practical work used to study the reaction below are given in the table (all results
Set up activities that allow are for a temperature of 973 K):
students to demonstrate what 2H2(g) + 2NO(g) → 2H20(g) + N2(g) they have learned in this unit. –2 –3 –2 –3 –6 –3 –1 The activities can be provided [H2] / 10 mol dm [NO] / 10 mol dm rate /10 mol dm s informally or formally during 2.0 2.50 4.8 and at the end of the unit, or for homework. They can be 2.0 1.25 1.2 selected from the teaching 2.0 5.00 19.2 activities or can be new experiences. Choose tasks 1.0 1.25 0.6 and questions from the 4.0 2.50 9.6 examples to incorporate in the activities. a. What is the order of reaction with respect to: i. hydrogen; ii nitrogen monoxide? b. Write a rate expression for the reaction. c. Calculate the rate constant for this reaction at 973 K.
From G. Burton, 2000, Salters Advanced Chemistry, Chemical Ideas, 2nd edn, Heinemann, p.239
Prepare a presentation for a group of Grade 11 students to explain why the rate of a chemical reaction increases with temperature.
Design an investigation to determine the equilibrium constant for the reaction between ethyl ethanoate and water at 298 K. (Note: The reaction is very slow and mixtures will need 48 hours to equilibrate. 2 mol dm–3 hydrochloric acid may be used as a catalyst for the reaction.)
469 | Qatar science scheme of work | Grade 12 advanced | Unit 12AC.2 | Chemistry 2 © Education Institute 2005
470 | Qatar science scheme of work | Grade 12 advanced | Unit 12AC.2 | Chemistry 2 © Education Institute 2005 GRADE 12A: Chemistry 3 UNIT 12AC.3 7 hours Acids and K values
About this unit Previous learning Resources
This unit is the third of eight units on chemistry To meet the expectations of this unit, students should already be able to The main resources needed for this unit are: for Grade 12 advanced. distinguish between strong and weak acids and alkalis, perform • strong acids at different concentrations The unit is designed to guide your planning and neutralisation titrations, make salts and know the mechanism by which the • range of weak acids and salts (e.g. ethanoic acid and sodium ethanoate) pH of buffer solutions remains stable. teaching of chemistry lessons. It provides a link • titration graphs (pH versus volume)
between the standards for science and your • range of data (see ‘Notes’ column for details) lesson plans. Expectations • Internet access The teaching and learning activities should help you to plan the content and pace of lessons. By the end of the unit, students address mathematically problems related to acid–base reactions, buffer solutions and solutions of sparingly soluble Adapt the ideas to meet your students’ needs. Key vocabulary and technical terms salts. For consolidation activities, look at the scheme of Students should understand, use and spell correctly: work for Grade 10. Students who progress further address mathematically problems related • strong and weak acids, pH, K , pK , K , indicator, buffer to acid–base reactions, buffer solutions and solutions of sparingly soluble a a w You can also supplement the activities with • solubility product Ksp appropriate tasks and exercises from your salts with a full mathematical appreciation of even complex examples.
school’s textbooks and other resources. Introduce the unit to students by summarising what they will learn and how this builds on earlier work. Review the unit at the end, drawing out the main learning points, links to other work and real world applications.
471 | Qatar science scheme of work | Grade 12 advanced | Unit 12AC.3 | Chemistry 3 © Education Institute 2005 Standards for the unit Unit 12AC.3
SUPPORTING STANDARDS CORE STANDARDS EXTENSION STANDARDS 7 hours Grade 12 standards
2 hours 10A.21.7 Understand and use the Brønsted– 12A.20.10 Show an understanding of the Brønsted–Lowry theory of acidity. Derive Lowry theory of acids and bases. and explain the terms pH, K , pK and K , and use these concepts in pH a a w calculations such as the calculation of the pH of solutions of weak acids
and bases. 2 hours 10A.21.3 Explain the changes in pH during 12A.20.11 Know that indicators are weak acids and explain the choice of suitable Indicators neutralisation and justify the choice indicators in acid–base titrations, in terms of the dissociation constant of of indicator. the indicator.
– 2 hours 10A.21.5 Know the mechanism by which the 12A.20.12 Understand how buffer solutions control pH (including the role of HCO3 in Buffers pH of buffer solutions remains stable, controlling blood pH) and calculate the pH of buffer solutions, given give examples and state their appropriate data.
composition. 1 hour 12A.20.13 Apply quantitatively the concept of dynamic equilibrium to the solubility of Solubility ionic compounds by calculating the solubility product Ksp from products concentrations, and vice versa, and demonstrate an understanding of the common ion effect.
472 | Qatar science scheme of work | Grade 12 advanced | Unit 12AC.3 | Chemistry 3 © Education Institute 2005 Activities Unit 12AC.3
Objectives Possible teaching activities Notes School resources
pH Revise the notion that acids are proton donors. Ask students to research the definitions of pH, Supply reference data on the pH of a range of Use this column to note K , pK and K and present their findings to the rest of the group. strong acids. your own school’s 2 hours a a w Then ask them to carry out calculations to determine the pH for a range of strong acids of given Students will need a range of strong acids at resources, e.g. Show an understanding of concentration using pH = –log [H+(aq)].They can then actually measure the pH of those different concentrations. textbooks, worksheets. the Brønsted–Lowry theory of solutions. acidity. Derive and explain Enquiry skills 12A.3.1, 12A.3.3
the terms pH, Ka, pKa and Kw, Guide students in through the assumptions made in order to derive the term Ka for a weak acid. and use these concepts in Then get them to work through a range of calculations using this term. Let them mark each calculations such as the other’s work and give each other feedback. Then ask them to consider the use of pKa and do calculation of the pH of worked examples interconverting Ka and pKa. solutions of weak acids and Raise the case of water for students to consider and introduce data that will allow them to bases. calculate the pH of water at 298 K to be 7. They can then use Kw to calculate the pH of bases.
Indicators Give students titration graphs of pH versus volume of acid added to alkali for a range of strong Students will need titration graphs for strong and and weak acid combinations. From this data they will be able to determine the pH range over weak acid combinations and data on indicators. 2 hours which a colour change is required for a certain acid–base combination. Also give them Ka values Enquiry skills 12A.4.1, 12A.4.2 Know that indicators are for a range of common indicators. They can use this information to determine the pH at which a weak acids and explain the given indicator changes colour and match the correct indicator to the correct acid–base titration. choice of suitable indicators If there is enough time, ask them to carry out an acid–base titration using different indicators to in acid–base titrations, in check their calculations were correct. terms of the dissociation constant of the indicator.
Buffers Ask small groups of students to make short presentations on Grade 10 work explaining the mechanism by which weak acid/salt systems function as buffering systems. Lead them through 2 hours + the assumptions needed to derive the expression Ka = [H ] × [salt]/[acid]. Understand how buffer Provide data that lets students consider how different acid/salt systems allow solutions of Provide suitable data on buffer systems. solutions control pH – different areas of the pH scale to be made up and how altering the ratio of salt to acid in a given (including the role of HCO3 in buffer system can alter the pH exactly to the desired pH. controlling blood pH) and calculate the pH of buffer Ask students to design a buffer system for a given pH, calculate its composition, make it up and Students will need a selection of weak acids and solutions, given appropriate measure the actual pH of the system. their salts. data. Ask students to use the Internet or other sources to research the control of pH in the blood and ICT opportunity: Use of the Internet. make poster presentations of their findings. Enquiry skill 12A.3.4
473 | Qatar science scheme of work | Grade 12 advanced | Unit 12AC.3 | Chemistry 3 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
Solubility products Once students have considered the idea that even seemingly ‘insoluble’ salts are sparingly Provide a range of calculations and data. soluble, introduce the definition of K . Allow them to practise calculations to determine the 1 hour sp solubility product Ksp from concentrations, and vice versa. Ask them to calculate whether a Apply quantitatively the precipitate will form when two solutions are mixed together by calculating whether Ksp has been concept of dynamic exceeded. The data you provide for the latter type of problems should include examples of equilibrium to the solubility of common ions (e.g. how the solubility of silver chloride varies with water as a solute as opposed ionic compounds by to 1 mol dm–3 hydrochloric acid as the solute). calculating the solubility
product Ksp from concentrations, and vice versa, and demonstrate an understanding of the common ion effect
474 | Qatar science scheme of work | Grade 12 advanced | Unit 12AC.3 | Chemistry 3 © Education Institute 2005 Assessment Unit 12AC.3
Examples of assessment tasks and questions Notes School resources
Assessment Calculate the pH of the following solutions: –3 –5 –3 Set up activities that allow i. 0.125 mol dm ethanoic acid (Ka = 1.7 x 10 mol dm ); –3 students to demonstrate what ii. 2.0 mol dm H2SO4; they have learned in this unit. –3 iii. 0.1 mol dm NaOH. The activities can be provided informally or formally during What would be the colour of cresol red in a solution of: and at the end of the unit, or i. 0.1 mol dm–3 sodium hydroxide; for homework. They can be ii. 0.1 mol dm–3 hydrochloric acid; selected from the teaching activities or can be new pKa cresol red = 8.2 / pH range = 7.2–8.8 / colour range yellow to red. experiences. Choose tasks Justify your answer in detail. and questions from the Enquiry skill 12A.1.8 examples to incorporate in Research and write a 1000-word account of the importance of buffers in living systems. the activities. –5 2 –6 3 Ksp for silver bromate(V) AgBrO3 is 6.0 × 10 mol dm at 298 K. 100 cm of 0.01 M silver nitrate solution is added to 200 cm3 of 0.01 M potassium bromate(V) solution. Calculate whether a precipitate would form. Show all workings.
475 | Qatar science scheme of work | Grade 12 advanced | Unit 12AC.3 | Chemistry 3 © Education Institute 2005
476 | Qatar science scheme of work | Grade 12 advanced | Unit 12AC.3 | Chemistry 3 © Education Institute 2005 GRADE 12A: Chemistry 4 UNIT 12AC.4 16 hours Energy and entropy
About this unit Previous learning Resources
This unit is the fourth of eight units on chemistry To meet the expectations of this unit, students should already know and be The main resources needed for this unit are: for Grade 12 advanced. able to use the concepts of enthalpy of reaction and activation energy and • cards with names, symbols and definitions of enthalpy changes The unit is designed to guide your planning and associate endothermic and exothermic changes with bond breaking and • ammonium chloride, polystyrene cups, thermometers making. teaching of chemistry lessons. It provides a link • assortment of liquid fuels (e.g. pentane), spirit burners, copper
between the standards for science and your calorimeters, balances lesson plans. Expectations • 1 mol dm–3 HCl, 1 mol dm–3 NaOH The teaching and learning activities should help • small whiteboards (class set) By the end of the unit, students use mathematically the concepts of you to plan the content and pace of lessons. • potassium hydrogen carbonate, potassium carbonate enthalpy change and relate them to energy cycles. They understand the Adapt the ideas to meet your students’ needs. • cards with names, symbols and definitions of terms used in Born–Haber For consolidation activities, look at the scheme of application of the second law of thermodynamics to chemical systems and cycles work for Grade 10A. can use the concepts of entropy and free energy in relation to the spontaneity of a reaction. • animation of a Born–Haber cycle and suitable data You can also supplement the activities with 2 • square cards (3 cm ) in two different colours six of each) and two dice, per appropriate tasks and exercises from your Students who progress further use mathematically the concepts of pair of students school’s textbooks and other resources. enthalpy change and relate them to more complex energy cycles. They understand the application of the second law of thermodynamics to more • selection of standard molar entropy values and enthalpy changes of Introduce the unit to students by summarising complex chemical systems and can use the concepts of entropy and free reaction values what they will learn and how this builds on earlier energy in relation to the spontaneity of a reaction at different temperatures. • video clips of the reaction of aluminium with iodine, and of sodium with work. Review the unit at the end, drawing out the chlorine main learning points, links to other work and real world applications. Key vocabulary and technical terms
Students should understand, use and spell correctly: • standard enthalpy change (∆H) of combustion, formation, solution and neutralisation • Hess’s law, energy cycle • Born–Haber cycle, standard enthalpy change of atomisation, ionisation, electron affinity, lattice energy θ θ θ • entropy, entropy change, ∆S total, ∆S system, ∆S surroundings • Gibbs free energy (∆G)
477 | Qatar science scheme of work | Grade 12 advanced | Unit 12AC.4 | Chemistry 4 © Education Institute 2005 Standards for the unit Unit 12AC.4
SUPPORTING STANDARDS CORE STANDARDS EXTENSION STANDARDS 16 hours Grade 12 standards
8 hours 10A.24.1 Know that chemical reactions are 12A.21.1 Explain and use the concept of standard enthalpy change (∆H), with accompanied by energy changes, particular reference to combustion, formation, solution and neutralisation. Enthalpy change usually in the form of heat energy, Calculate enthalpy changes from experimental results. and cycles and that the energy changes can be exothermic or endothermic. 4 hours 10A.24.4 Explain and use the concept of Entropy standard enthalpy change (∆H), with particular reference to combustion, formation, solution and 4 hours neutralisation, and calculate enthalpy Free energy changes from experimental results
10A.24.5 Recognise that bond breaking is associated with endothermic changes and bond formation is associated with exothermic changes
12A.21.2 Use Hess’s law to construct simple energy cycles and determine enthalpy changes that cannot be found by direct experiment, such as enthalpies of formation and of ionisation.
12A.21.3 Understand the concept of the Born–Haber cycle and use it to determine unknowns such as electron affinity and ionisation energy.
12A.21.4 Understand how the natural tendencies in the Universe towards minimum potential energy and maximum disorder are reconciled in the second law of thermodynamics, and understand how these tendencies are applied to chemical systems.
12A.21.5 State and explain the factors that lead to an increase in the entropy (disorder) of a chemical system.
12A.21.6 Calculate the standard entropy change for a reaction using absolute entropy values and recognise and explain the impact of changes of state on this value.
12A.21.7 Calculate standard free energy changes for reactions from enthalpy and entropy changes and use this to predict the spontaneity of a reaction at a particular temperature.
478 | Qatar science scheme of work | Grade 12 advanced | Unit 12AC.4 | Chemistry 4 © Education Institute 2005 Activities Unit 12AC.4
Objectives Possible teaching activities Notes School resources
θ θ θ θ 8 hours Students should be familiar with the terms ∆H c, ∆H f, ∆H soln, ∆H neutralisation and standard Prepare suitable sets of cards. Use this column to note conditions from Grade 10 work. In order to consolidate their knowledge, ask students to work in your own school’s Enthalpy change and θ pairs on a card-matching activity. Each card has either a symbol (e.g. ∆H c), a name of a term resources, e.g. cycles (e.g. standard enthalpy of combustion) or an equation representing the term textbooks, worksheets.
Explain and use the concept (e.g. C(s) O2 → CO2(g)). Students need to make a trio of cards that link together. of standard enthalpy change Allocate (depending on the abilities of the students) a practical experiment to determine the Enquiry skills 12A.1.1–12A.1.5, 12A.3.1– (∆H), with particular reference enthalpy change of a given reaction. Alternatively, ask students, in groups, to plan and carry out 12A.3.4, 12A.4.1 to combustion, formation, their own practical investigation and then analyse and evaluate their results. solution and neutralisation. Calculate enthalpy changes Possible experiments include: θ from experimental results. • Determine ∆H soln for dissolving ammonium chloride in water (dissolve a known mass of Use Hess’s law to construct ammonium chloride in a known volume of water in an insulated vessel and record any simple energy cycles and temperature changes). θ determine enthalpy changes • Determine ∆H c for the combustion of different liquid fuels using a spirit burner to heat up a that cannot be found by direct known volume of water in a copper calorimeter. Record any changes in temperature. θ –3 experiment, such as • Determine ∆H neutralisation by mixing known volumes of 1 mol dm HCl with known volumes of enthalpies of formation and of 1 mol dm–3 NaOH in an insulated vessel and record any changes in temperature. ionisation. Students can then calculate the enthalpy change for their given reaction. Tell them to prepare a Understand the concept of short presentation for the rest of the class describing the planning, implementation, analysis and the Born–Haber cycle and evaluations they have carried out. They should also provide a handout sheet summarising the use it to determine unknowns practical work and the calculations involved. such as electron affinity and Lead a whole-class discussion to help students appreciate that it is not always easy to ionisation energy. determine the enthalpy change for some reactions, so they need to be determined indirectly. After explaining Hess’s law, go through two examples of enthalpy cycles, one to show how enthalpies of formation can be calculated using given data and a second to show how ionisation enthalpies can be calculated using given data. At each stage take care to reinforce definitions of all the terms used (e.g. by asking questions and asking students to write their answers on small whiteboards which they hold up so you can check their understanding easily and quickly). Ask students to work in pairs to determine practically the enthalpy change for the reaction of potassium hydrogen carbonate with hydrochloric acid and the reaction of potassium carbonate with hydrochloric acid. Then tell them to construct an enthalpy cycle and use their data to determine the enthalpy change for the thermal decomposition of potassium hydrogen carbonate.
θ Ask students, in pairs, to carry out a card-sort activity matching cards with terms on (e.g. ∆H LE), Prepare suitable sets of cards. to cards with the appropriate definition of terms. These will cover the terms needed in order to Enquiry skills 12A.3.1, 12A.3.2 be able to construct Born–Haber cycles. Lead a session to help students appreciate how to use Born–Haber cycles. It would be useful to have a PowerPoint (or similar) presentation that slowly builds up each stage of the process. Then give students data so that they can construct their own cycles in order to calculate θ θ θ different ∆H LE, ∆H EA and ∆H i values.
479 | Qatar science scheme of work | Grade 12 advanced | Unit 12AC.4 | Chemistry 4 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
4 hours This activity simulates the idea of molecular mixing. Ask students to work in pairs and give each Prepare suitable sets of cards. pair two sets of cards of different colours (each set numbered 1 to 6) and two dice. Tell students Entropy to take one set of cards and a die each and to lay out the cards on a sheet of paper, with all the Understand how the natural cards of the first colour close to each other and all the cards of the second colour close to each tendencies in the Universe other. This represents two pure unmixed liquids. Then ask each student to roll their die. The towards minimum potential numbers that come up tell them which of their cards to move (e.g. if one student (red cards) rolls energy and maximum a 6 and the other (blue cards) rolls a 2, then red card 6 swaps places with blue card 2). This disorder are reconciled in the represents the random movements of particles. Tell them to continue for 10 rolls of the dice and second law of then discuss in their pairs what would happen if they rolled 100 times, 1000 times and 10 000 thermodynamics, and times. What is the chance that the arrangement would ever return to that at the start of the understand how these activity? Draw out, through class discussion, how this activity accounts for diffusion and the tendencies are applied to mixing of liquids by imagining what the situation would be with millions of particles. Draw out the chemical systems. idea that there are many more ways of mixing particles than of separating them. Entropy is a State and explain the factors measure of the number of ways something can be arranged. that lead to an increase in the Give students a list of standard entropy values for a range of solids, liquids and gases and ask entropy (disorder) of a them to look for any patterns in the data. chemical system. Ask students to come up with as many examples as they can of a tendency towards disorder in Calculate the standard their everyday lives (e.g. what happens to an uninhabited house over a number of years). entropy change for a reaction Show the whole class a video clip of the reaction of aluminium powder with iodine (an using absolute entropy values exothermic reaction in which clouds of iodine vapour are released). Ask them to consider what and recognise and explain energy transfers are taking place. Now view the film backwards and point out that this does not the impact of changes of happen and ask why. Use this as a model for class discussion to draw out the idea that ‘energy state on this value. seems to spread out’ and there is a tendency towards disorder or chaos called entropy. Introduce the term quanta of energy and ask students to consider how different numbers of quanta of energy can be distributed between two molecules. Ask students to consider the types of energy present in a molecule and what will happen to the number of quanta of energy if a substance is heated. Introduce the second law of thermodynamics, which states that: No process is possible in which there is an overall decrease in the entropy of the Universe. Give students standard molar entropy values for the reaction of the conversion of ozone to Enquiry skills 12A.3.1, 12A.3.2 oxygen and show the whole class how to calculate the standard entropy change for the reaction. Give them a number of examples to practise, all giving increases in entropy. Once the students are happy with these calculations, give them values that allow them to calculate the entropy change for the formation of sodium chloride from sodium and chlorine. This gives a negative value, so students should predict that the reaction will not occur. Show them a video clip of sodium reacting violently with chlorine gas and ask why this occurs spontaneously. Introduce the idea of total entropy change being the sum of the entropy change of the system added to the entropy change of the surroundings. Explain that students have so far only θ θ calculated ∆S sys. Introduce the relationship ∆S surroundings = –∆H ⁄ T. Allow students to practise θ calculating examples individually. Now give them data so they are able to calculate ∆S total for the formation of sodium chloride (as above). Allow them to practise a variety of examples.
480 | Qatar science scheme of work | Grade 12 advanced | Unit 12AC.4 | Chemistry 4 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
4 hours Derive the equation –T∆Stotal (∆G) = ∆H – T∆Ssys. Enquiry skills 12A.3.1, 12A.3.2
Free energy In class discussion, draw out the idea that, since ∆Stotal must be positive for a spontaneous reaction, then ∆G must be negative. Calculate standard free energy changes for reactions Ask students to break into four groups. Their task is to use the relationship ∆G = ∆H – T∆Ssys from enthalpy and entropy for one of the four scenarios below to decide whether a reaction will be spontaneous or not. Ask changes and use this to each group to report their findings to the whole class. The scenarios are: predict the spontaneity of a • exothermic reactions accompanied by an increase in entropy; reaction at a particular • exothermic reactions accompanied by a decrease in entropy; temperature. • endothermic reactions accompanied by an increase in entropy; • endothermic reactions accompanied by a decrease in entropy. Give students data for the decomposition of calcium carbonate at different temperatures and ask them to calculate whether the reaction will be spontaneous or not. Ask them to calculate the lowest temperature at which the reaction will become spontaneous.
481 | Qatar science scheme of work | Grade 12 advanced | Unit 12AC.4 | Chemistry 4 © Education Institute 2005 Assessment Unit 12AC.4
Examples of assessment tasks and questions Notes School resources
Assessment Draw an enthalpy cycle to show the relationship between the combustion of ethanal Set up activities that allow (CH3CHO(l)) and the formation of ethanal, carbon dioxide and water to form carbon, hydrogen students to demonstrate what and oxygen. Use this cycle to calculate the standard enthalpy change of combustion of ethanal. θ –1 θ –1 θ –1 they have learned in this unit. ∆H f (CH3CHO) = –192 kJ mol ; ∆H f (CO2) = –393 kJ mol ; ∆H f (H2O) = –286 kJ mol The activities can be provided Adapted from G. Burton, 2000, Salters Advanced Chemistry, Chemical Ideas, 2nd edn, informally or formally during Heinemann, p.63 and at the end of the unit, or for homework. They can be Draw a Born–Haber cycle for calcium chloride in the form of an enthalpy level diagram. selected from the teaching Use the following data to explain why water freezes at 0 °C at atmospheric pressure activities or can be new θ –1 –1 experiences. Choose tasks ∆S sys = –22.0 kJ mol , ∆H = –60.1 kJ mol
and questions from the θ –1 The enthalpy change of vapourisation ∆H vap of trichloromethane is +29.7 kJ mol . The change examples to incorporate in CH Cl(l) → CH Cl(g) the activities. 3 3 –1 –1 has ∆Ssys = +88.7 J mol K . At what temperature will the trichloromethane boil? Adapted from A. Fullick and P. Fullick, 2000, Heinemann Advanced Science: Chemistry, 2nd edn, Heinemann Educational, p.354
482 | Qatar science scheme of work | Grade 12 advanced | Unit 12AC.4 | Chemistry 4 © Education Institute 2005 GRADE 12A: Chemistry 5 UNIT 12AC.5 11 hours Organic reaction mechanisms
About this unit Previous learning Resources
This unit is the fifth of eight units on chemistry for To meet the expectations of this unit, students should already know the The main resources needed for this unit are: Grade 12 advanced. significance of s, p, d and f orbitals and hybrids in bonding and molecular • long thin balloons, Peel models, computer animations of molecular The unit is designed to guide your planning and shape, and distinguish between σ and π bonds. They should have an structures teaching of chemistry lessons. It provides a link understanding of the general chemistry of alkanes, alkenes, • L-carvone, D-carvone, tin foil, caraway seeds, spearmint (or spearmint between the standards for science and your halogenoalkanes, aldhehydes, ketones, acyl chlorides, amines and amides. chewing gum)
lesson plans. The teaching and learning activities should help Expectations Key vocabulary and technical terms you to plan the content and pace of lessons. By the end of the unit, students understand the mechanisms of Adapt the ideas to meet the needs of your class. Students should understand, use and spell correctly: electrophilic addition and substitution, nucleophilic substitution and For consolidation activities, look at the scheme of • aliphatic, orbitals, electron-pair repulsion elimination reactions. work for Grade 11A. • chiral centre, optical isomerism, enantiomer Students who progress further show an understanding of the Lewis You can also supplement the activities with • reaction mechanism theory of acids and bases and relate it to nucleophilic reactions in organic appropriate tasks and exercises from your • Lewis acid chemistry. school’s textbooks and other resources. • hydrolysis, acylation, acylating agent Introduce the unit to students by summarising • phenylamine, butylamine, ammonia solution, dilute hydrochloric acid what they will learn and how this will build on earlier work. Review the unit at the end, drawing out the main learning points, links to other work and real world applications.
483 | Qatar science scheme of work | Grade 12 advanced | Unit 12AC.5 | Chemistry 5 © Education Institute 2005 Standards for the unit Unit 12AC.5
SUPPORTING STANDARDS CORE STANDARDS EXTENSION STANDARDS 11 hours Grade 12 standards
3 hours 11A.18.10 Describe covalent bonding in terms 12A.22.1 Describe the shape of aliphatic organic compounds in terms of orbital of orbital overlap, giving σ (sigma) overlap and electron-pair repulsion. Bonding in and π (pi) bonds; explain bond shape organic 12A.22.2 Describe the restricted rotation and the resulting stereochemistry of and angles in ethane, ethene and multiple bonds in terms of σ (sigma) and π (pi) bonds. chemistry benzene in terms of σ and π bonds.
11A.24.5 Illustrate structural and geometric 12A.22.3 Describe structural isomerism, cis–trans isomerism in alkenes, and how 4 hours isomerism in alkanes and alkenes. chiral centres give rise to optical isomerism. Electrophilic 11A.24.9 Describe the chemistry of 12A.22.4 Describe the mechanisms of electrophilic addition in alkenes and addition and halogenoalkanes as exemplified by nucleophilic substitution in compounds such as halogenoalkanes. nucleophilic substitution reactions and the substitution elimination of hydrogen halide to form an alkene. 2 hours 11A.24.4 Describe the chemistry of alkenes as the chemistry of the double bond, Acylation exemplified by addition and polymerisation. 2 hours 12A.22.5 Show an understanding of the Lewis theory of acids and bases and relate it Amines and to nucleophilic reactions in organic chemistry. amides 11A.24.13 Describe the chemistry of the 12A.22.6 Describe the chemistry of the carbonyl group in terms of nucleophilic carbonyl group as exemplified by substitution and show how its reactivity depends on the electronegativity of
aldehydes and ketones. the group or groups attached to it. 12A.22.7 Know that acyl chlorides (exemplified by ethanoyl chloride) are readily hydrolysed and that they are useful agents for acylating alcohols, phenols and amines. 12A.22.8 Distinguish between amines and amides, recognise that they are both substituted ammonia compounds and therefore describe their basic properties.
484 | Qatar science scheme of work | Grade 12 advanced | Unit 12AC.5 | Chemistry 5 © Education Institute 2005 Activities Unit 12AC.5
Objectives Possible teaching activities Notes School resources
3 hours Guide students through the first example given below. Use this column to note your own school’s Bonding in organic Arrange students into pairs and get them to inflate long thin balloons and twist them in the resources, e.g. chemistry middle. Each ‘lobe’ of the balloon represents a group of electrons in a molecule around a central atom. A group of electrons might be a lone pair of electrons, a single, double or triple textbooks, worksheets. Describe the shape of covalent bond. Ask students to model various atoms in molecules (e.g. the carbon in aliphatic organic compounds methane could be represented by twisting two bilobar balloons together). The lobes in terms of orbital overlap automatically arrange themselves into a pyramidal conformation with a bond angle and electron-pair repulsion. approximating to 109°. Describe the restricted Introduce students to the convention for representing 3D structures in 2D and ask them to ICT opportunity: Use of the Internet and Java rotation and the resulting draw out the structure of methane. Reinforce their appreciation of the structure using either applets. stereochemistry of multiple 3D Peel models or applets downloaded from the Internet. bonds in terms of σ (sigma) and π (pi) bonds. Give students the names of a range of organic compounds (e.g. ethanal, trimethylamine) and ask them to work in pairs, using the technique above, to work out the 3D structure of the Describe structural compounds. Differentiate the complexity of the molecules to suit students’ ability. For each isomerism, cis–trans example, ask students to relate the balloon models to the type of bonds (e.g. of σ (sigma) isomerism in alkenes, and and π (pi) bonds). how chiral centres give rise to optical isomerism Revise the formation of σ (sigma) and π (pi) bonds. Ask students, working individually, to make models of ethane and ethene using a model building kit. Revise the formation of σ (sigma) and π (pi) bonds and ask them to draw diagrams showing the types of bonds involved in the two
different molecules. Give students the bond enthalpy values for the carbon–carbon bonds in
both molecules and ask them to interpret the difference in the bond enthalpies and discuss their
ideas in pairs. Ask each student to build a model of but-2-ene. Ask them to compare their model
with those of the rest of the class and form two groups. Each group will consist of students producing the same form of but-2-ene. Draw the two different structures on the board or OHP and discuss with the whole class the difference between the two forms, why they do not readily interconvert at room temperature and the possible impact on reactivity (steric hindrance). Then ask students to use their textbook, the library or the Internet to research the differences in ICT opportunity: Use of the Internet. chemical reactivity and physical properties for given cis–trans isomers. Ask students to build a ‘ball and stick’ model using a central carbon with four different coloured groups attached. (All students must use the same four colours.) Ask them to compare their model first with the person to the left of them then with the person to the right of them. Ask them to identify whether the compounds are the same as or different from each other. Ask them to identify the link between the two non-superimposable models (i.e. they are mirror images of each other). Ask students to draw a 3D representation of an amino acid. Introduce the terms enantiomer and chiral centre.
485 | Qatar science scheme of work | Grade 12 advanced | Unit 12AC.5 | Chemistry 5 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
Prepare small tubes wrapped in tin foil and plugged with cotton wool. Place a few drops of L-carvone in one-third of the tubes and label as ‘compound X’. Place a few drops of D-carvone in another one-third of the tubes and label as ‘compound Y’. Divide the remaining one-third of the tubes into two and place freshly ground caraway seeds (contains D-carvone) in half of them and fresh spearmint (contains L-carvone) in the other half. Label these ‘spearmint’ and ‘caraway’ as appropriate. Let all students smell compound X then compound Y to decide whether they smell the same or different. Then let them smell the caraway and spearmint to see whether they smell the same as X or Y. (Caraway seeds contain D-carvone and spearmint contains L-carvone). Gather data from the whole class. Show students the structures of D- and L-carvone and ask them to work in pairs to identify the chiral centre. Ask them to try to explain why not everyone could differentiate between L- and D-carvone. Ask students to use the Internet to research the use of thalidomide and relate the resultant ICT opportunity: Use of the Internet. problems to optical isomerism. Ask them to prepare a report detailing the case, making Enquiry skills 12A.2.2, 12A.2.3 recommendations on how this scenario could be prevented in the future.
4 hours In a teacher-led session, teach the mechanism for electrophilic addition in alkenes. Provide a generic model of the reaction. Ask students to work through a number of reactions they Electrophilic addition and researched in Grade 11 and draw out the full mechanism for these reactions. Take great care to nucleophilic substitution reinforce the conventions of single- and double-headed arrows to represent the movement of Describe the mechanisms of one and two electrons, respectively. Let students mark each other’s work. electrophilic addition in In a teacher-led session, teach the mechanisms for nuleophilic substitution reactions. Provide a alkenes and nucleophilic generic model of each of the mechanisms. Ask students to work through a number of reactions substitution in compounds they researched in Grade 11 and draw out the full mechanism for these reactions. Let students such as halogenoalkanes. mark each other’s work. Show an understanding of the Lewis theory of acids and Revise the definition of a nucleophile in a whole class question and answer session. bases and relate it to Give students the definition of a Lewis acid and Lewis base in terms of electron transfer. Give nucleophilic reactions in them a list of reactions (e.g. the production of butan-1-ol by the reaction of 1-bromobutane with organic chemistry. hydroxide ions) and ask them to identify the Lewis acids and bases in each reaction. Ask each Describe the chemistry of the student to identify another reaction and the Lewis acids and bases involved in the reaction. carbonyl group in terms of nucleophilic substitution and Supply data on the reactivity of different carbonyl compounds and electronegativity data for Enquiry skills 12A.3.2 show how its reactivity different elements. Tell students to rank these compounds with respect to order of reactivity. depends on the Ask them to account for the differing reactivities by noting the extent to which the atom (or electronegativity of the group group) attached to the carbonyl group tends to oppose or enhance the movement of electrons or groups attached to it. away from the carbonyl carbon atom.
486 | Qatar science scheme of work | Grade 12 advanced | Unit 12AC.5 | Chemistry 5 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
2 hours Write an equation for the hydrolysis of ethanoyl chloride on the board or OHP. Ask students to Acylation write a similar equation for the hydrolysis of an acyl chloride of their choice. Know that acyl chlorides Ask students to use their textbook, the library or the Internet to research the uses of ethanoyl ICT opportunity: Use of the Internet. (exemplified by ethanoyl chloride in acylating alcohols, phenols and amides. Let them work in small groups to produce chloride) are readily information posters for these reactions. hydrolysed and that they are Tell students to carry out the following procedure and record their results. Add ethanoyl chloride Safety: All work must be carried out in a fume useful agents for acylating dropwise to 10 drops of butylamine in a dry test-tube and observe any reaction. Add a small cupboard. Ethanoyl chloride is corrosive and an alcohols, phenols and volume (1 cm depth) of water. Add sodium hydroxide solution, warm and test any gases irritant. amines. evolved with damp red litmus paper. Use class discussion to interpret the results Enquiry skills 12A.3.1, 12A.3.4, 12A.4.1
2 hours Ask students to draw the structure of a primary amine, secondary amine, tertiary amine, primary amide and secondary amide. Draw up the structure of ammonia on the board or OHP and use Amines and amides questioning to draw out the relationship between these compounds. Distinguish between amines and amides, recognise that Ask students, working individually, to test the reaction of phenylamine, butylamine and Safety: Phenylamine is toxic. Use in small they are both substituted ammonia solution with water and universal indicator. quantities in the fume cupboard. Butylamine is ammonia compounds and 3 flammable and an irritant. therefore describe their basic Tell them to shake two drops of phenylamine with 2 cm of dilute hydrochloric acid, then repeat properties. with butylamine and record their results. Let them interpret their observations in small group Enquiry skills 12A.3.1, 12A.3.4, 12A.4.1 discussions and ask each group to report back to the whole class for a whole group discussion.
487 | Qatar science scheme of work | Grade 12 advanced | Unit 12AC.5 | Chemistry 5 © Education Institute 2005 Assessment Unit 12AC.5
Examples of assessment tasks and questions Notes School resources
Assessment a. Write a reaction mechanism for the reaction of ammonia with bromobutane. Set up activities that allow b. Describe why the reaction occurs this way. students to demonstrate what c. What reaction conditions are needed? they have learned in this unit. d. Why is this classified as a substitution reaction? The activities can be provided
informally or formally during a. Draw a dot and cross diagram for the molecule CH3─N═N─CH3. and at the end of the unit, or b. Draw out the structure of the compound in part a showing all the bond angles. for homework. They can be c. This compound can exist as cis and trans isomers. Draw diagrams to show the two selected from the teaching structures. activities or can be new experiences. Choose tasks a. Draw the structural formula of 3-methylhexane.
and questions from the b. Identify the chiral carbon in your structure with an asterisk (∗). examples to incorporate in c. Use three-dimensional diagrams to show the structures of the two optical isomers of this the activities. compound.
Write an account of the similarities between the chemistry of ammonia, amines and amides.
488 | Qatar science scheme of work | Grade 12 advanced | Unit 12AC.5 | Chemistry 5 © Education Institute 2005 GRADE 12A: Chemistry 6 UNIT 12AC.6 11 hours Aromatic organic chemistry
About this unit Previous learning Resources
This unit is the sixth of eight units on chemistry To meet the expectations of this unit, students should already know how to The main resources needed for this unit are: for Grade 12 advanced. distinguish between σ and π bonds and recognise the relative unreactivity of • 0.01 mol dm–3 potassium manganate(VII), 1 mol dm–3 sulfuric acid, methyl The unit is designed to guide your planning and the arene ring. benzene
teaching of chemistry lessons. It provides a link • class set of student whiteboards between the standards for science and your Expectations • molecular model kits lesson plans. • methyl benzoate, concentrated sulfuric acid, concentrated nitric acid, ice By the end of the unit, students know the fundamental chemistry of The teaching and learning activities should help • methylphenol, phenol, phenylamine, sodium nitrate(III), sodium hydroxide, arenes and substituted arenes and describe the production of the more you to plan the content and pace of lessons. napthalen-2-ol, ice, fume cupboard important derivatives of benzene. They explain the stability of the benzene Adapt the ideas to meet your students’ needs. • Internet access ring in terms of electron delocalisation. For consolidation activities, look at the scheme of work for Grade 11A. Students who progress further understand the mechanism of electrophilic substitution reactions and are able to predict the effect of substitutions on You can also supplement the activities with Key vocabulary and technical terms the aromatic ring. appropriate tasks and exercises from your Students should understand, use and spell correctly: school’s textbooks and other resources. • arenes, aromatic Introduce the unit to students by summarising • electrophilic substitution what they will learn and how this builds on earlier • azo dyes, coupling, diazotisation work. Review the unit at the end, drawing out the main learning points, links to other work and real world applications.
489 | Qatar science scheme of work | Grade 12 advanced | Unit 12AC.6 | Chemistry 6 © Education Institute 2005 Standards for the unit Unit 12AC.6
SUPPORTING STANDARDS CORE STANDARDS EXTENSION STANDARDS 11 hours Grade 12 standards
4 hours 11A.24.1 Know, interpret and use the 112A.23.1 Interpret and use the nomenclature and structural formulae of the following nomenclature and molecular and classes of compound: Nomenclature of structural formulae of the following • arenes; arenes classes of compound: • halogenoarenes; • alkanes and alkenes; • phenols; 1 hour • halogenoalkanes; • aromatic aldehydes and ketones; • alcohols; • aromatic carboxylic acids, esters and acyl chlorides; Bonding in • aldhehydes and ketones; • aromatic amines, nitriles, amides and amino acids. arenes • carboxylic acids, esters and acyl
chlorides; 4 hours • amines, nitriles, amides and amino Reactions of acids arenes 11A.18.10 Describe covalent bonding in terms of 12A.23.2 Describe the shapes of the ethane, ethene and benzene molecules in orbital overlap, giving σ (sigma) and π terms of σ and π carbon–carbon bonds. (pi) bonds; explain bond shape and 2 hours angles in ethane, ethene and Azo dyes benzene in terms of σ and π bonds.
11A.24.18 Describe the chemistry of arenes (such 12A.23.3 Describe the chemistry of arenes (such as benzene and methylbenzene), as benzene and methylbenzene) and as exemplified by substitution reactions with electrophiles, nitration and show an understanding of the relative oxidation of the side chain. unreactivity of the aromatic ring compared with an isolated double bond; know that the chemistry of side chains is similar to that of aliphatic compounds.
11A.24.20 Compare the preparation and 12A.23.4 Understand the mechanism of electrophilic substitution in arenes and the properties of bromobenzene with effect of the delocalisation of electrons in arenes in such reactions. bromoethane to show the effect of the benzene ring.
11A.24.19 Know the chemistry of phenol, as 12A.23.5 Know the chemistry of phenol, as exemplified by its reactions with bases exemplified by its reactions with and sodium and by electrophilic substitution in the aromatic ring. bases and sodium, and know of its 12A.23.6 Describe the formation of aromatic amines by the reduction of nitroarenes. common use as a mild disinfectant.
11A.24.20 Show an understanding of the broad 12A.23.7 Describe the production of azo-dyes from phenylamine and understand issues relating to social benefits and their commercial importance. environmental costs associated with the organic chemical industry.
490 | Qatar science scheme of work | Grade 12 advanced | Unit 12AC.6 | Chemistry 6 © Education Institute 2005 Activities Unit 12AC.6
Objectives Possible teaching activities Notes School resources
4 hours For each of the classifications of compound listed in the standard (i.e. arenes; halogenoarenes; Use this column to note phenols; aromatic aldehydes and ketones; aromatic carboxylic acids, esters and acyl chlorides; your own school’s Nomenclature of arenes aromatic amines, nitriles, amides and amino acids) go through the following method to resources, e.g. Interpret and use the consolidate student understanding of nomenclature: textbooks, worksheets. nomenclature and structural • Write the name of the relevant class of aliphatic compound previously met in the course formulae of the following (e.g. halogenoalkanes if you intend teaching halogenoarenes) and a structure of examples of classes of compound: aliphatic analogues (if appropriate) on the board or OHP. • arenes; • Ask students to draw the structure of the named compound and the name of the structure • halogenoarenes; onto a small whiteboard and hold it up for you to see. • phenols; • The degree of revision of nomenclature for these compounds will depend on students’ • aromatic aldehydes and responses. If they appear to be confident, just summarise the rules for nomenclature for this ketones; class of compound. If they are not confident, reinforce the rules and give them more • aromatic carboxylic acids, examples of compound names and structures. Let them work in pairs and mark each other’s esters and acyl chlorides; work, explaining any incorrect answers to their partner. • aromatic amines, nitriles, • Explain to the whole class the extra information needed to be able to name the aromatic amides and amino acids. analogues. Repeat the above process for the aromatic analogues of the aliphatic compounds you have covered.
1 hour Revise, through a question and answer session, the shape and type of bonding in ethane and Two good websites are: ethene molecules. Bonding in arenes • www.chemguide.co.uk/basicorg/bonding/ Give students data relating to the enthalpy change of hydrogenation of cyclohexene and ask benzene1.html Describe the shapes of the them to draw an enthalpy level diagram for the hydrogenation of ‘cyclohexatriene’. Provide them • classes.yale.edu/chem220a/studyaids/ ethane, ethene and benzene with data for the enthalpy change of hydrogenation of benzene and ask them to superimpose history/chemists/kekule.html molecules in terms of σ and π this value onto their enthalpy level diagram. Provide them with data for C–C and C=C as well as carbon–carbon bonds. the carbon–carbon bond length in benzene. Ask them to explain this. Ask students to use the library or the Internet to research the work of Friedrich Kekulé and, ICT opportunity: Use of the Internet. working in small groups, produce a poster of his work. Enquiry skills 12A.2.1, 12A.2.4
491 | Qatar science scheme of work | Grade 12 advanced | Unit 12AC.6 | Chemistry 6 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
4 hours Tell students to mix equal volumes of 0.01 mol dm–3 potassium manganate(VII) and 1 mol dm–3 Safety: Methyl benzene is flammable. Reactions of arenes sulfuric acid with a few drops of methyl benzene. Tell them to observe colour changes and so determine whether the manganate(VII) oxidised the methylbenzene. Describe the chemistry of arenes (such as benzene and Draw the class together and give them the equation for this and other similar reactions. methylbenzene), as Explain to the whole class a general mechanism for the electrophilic substitution of benzene. ICT opportunity: Use of the Internet. exemplified by substitution Ask students to use the library or the Internet to research the conditions needed for bromination, reactions with electrophiles, chlorination, nitration, sulfonation, Friedel-Crafts alkylation and Friedel-Crafts acylation. Ask nitration and oxidation of the them, working individually, to produce a chart identifying the reaction conditions, the mechanism side chain. and the electrophile for each of these reactions. Understand the mechanism Give students the dipole moments for a number of monosubstituted benzene rings of electrophilic substitution in (e.g. phenylamine, chlorobenzene) and ask them to classify these into two groups: those that arenes and the effect of the are electron-withdrawing from the aromatic ring and those that are electron-releasing. Ask them delocalisation of electrons in to predict the effect of each group on reactivity in electrophilic substitution reactions. + arenes in such reactions. Guide students through drawing canonical forms for the attack of NO at the ortho position of + Know the chemistry of phenol then ask them to draw similar diagrams to show the canonical forms when NO attacks phenol, as exemplified by its at the meta position of phenol. Through class discussion and question and answer, explain why reactions with bases and the former is preferential. sodium and by electrophilic + Repeat the process for the attack of NO2 on benzoic acid. substitution in the aromatic Ask students, in pairs, to carry out an electrophilic substitution reaction. A suitable one is the Safety: Methyl benzoate is harmful, ring. nitration of chilled methyl benzoate in concentrated sulfuric acid, with a chilled nitrating mixture concentrated sulfuric acid and concentrated of concentrated sulfuric acid and concentrated nitric acid, keeping the temperature below 10 °C. nitric acid are corrosive. Crystallise the product out over ice. Enquiry skill 12A.4.1 Revise the reactions of phenol with bases and sodium (done as a practical in Grade 11) with a quiz.
2 hours Ask students to use the library or the Internet to research the work of Otto Witt and describe his ICT opportunity: Use of the Internet. contribution to the azo dye industry. Also ask them to research azo dye production worldwide Azo dyes Video footage of coupling reactions can be seen and present the data in a suitable format. on: www.uni-regensburg.de/Fakultaeten/ Describe the formation of Describe to the whole class the stages of synthesising an azo dye (i.e. diazotisation and nat_Fak_IV/Organische_Chemie/Didaktik/ aromatic amines by the coupling). Give students structures of a number of pairs of reactants and ask them (individually) Keusch/D-azo-e.htm. reduction of nitroarenes. to draw out the structure of the resultant dye. Also carry out the process in reverse. Safety: Methylphenol, phenol, phenylamine and Describe the production of Let students produce a range of azo dyes using phenylamine and ethyl-4-aminobenzoate as sodium nitrate(III) are toxic. Methylphenol, azo-dyes from phenylamine amines to prepare as diazonium salts. Tell them to prepare each diazonium salt by adding the phenol and sodium hydroxide solution are and understand their aryl amine to cooled dilute hydrochloric acid, cool below 5 °C. They should then add a cooled corrosive. Sodium nitrate(III) is an oxidising commercial importance. solution of sodium nitrate(III), not allowing the temperature to rise above 5 °C. agent. Napthalen-2-ol is harmful. Gloves and To prepare the coupling agents, chill phenol, 3-methylphenol and napthalen-2-ol, each made up goggles must be worn at all times. The work in alkaline solution, to below 5 °C. must be done in a fume cupboard. Tell students, working in pairs, to add each coupling agent slowly to each diazonium salt in turn Enquiry skills 12A.2.2, 12A.2.3, 12A.4.1 and observe the colours of the resultant dyes.
492 | Qatar science scheme of work | Grade 12 advanced | Unit 12AC.6 | Chemistry 6 © Education Institute 2005 Assessment Unit 12AC.6
Examples of assessment tasks and questions Notes School resources
Assessment If bromine water is added to a solution of phenylamine, a white precipitate of 2,4,6- Set up activities that allow tribromophenylamine forms. students to demonstrate what they have learned in this unit. Explain why the reaction occurs so readily. Suggest why the benzenediazonium ion attacks the The activities can be provided para rather than the ortho position on phenol. Draw the structure of the azo compound informally or formally during produced in this reaction. and at the end of the unit, or + for homework. They can be Give a generic mechanism for the electrophilic substitution of benzene with an electrophile E .
selected from the teaching Why is this reaction classified as an electrophilic substitution? activities or can be new experiences. Choose tasks Research and present a paper on the role of azo dyes in the organic chemical industry. Focus and questions from the on the reasons for and nature of the development of the industry. Reference clearly any examples to incorporate in sources of information. the activities.
493 | Qatar science scheme of work | Grade 12 advanced | Unit 12AC.6 | Chemistry 6 © Education Institute 2005
494 | Qatar science scheme of work | Grade 12 advanced | Unit 12AC.6 | Chemistry 6 © Education Institute 2005 GRADE 12A: Chemistry 7 UNIT 12AC.7 7 hours Making and using chemicals
About this unit Previous learning Resources
This unit is the seventh of eight units on To meet the expectations of this unit, students should already know a variety The main resources needed for this unit are: chemistry for Grade 12 advanced. of processes by which useful substances are made from raw materials, • class set of student whiteboards The unit is designed to guide your planning and including alkalis, chlorine and useful metals. They should know that the • Ellingham diagrams (class set) extractive industries can cause environmental degradation and should teaching of chemistry lessons. It provides a link • Internet access between the standards for science and your understand a variety of ways this can be minimised.
lesson plans. Key vocabulary and technical terms The teaching and learning activities should help Expectations you to plan the content and pace of lessons. Students should understand, use and spell correctly: By the end of the unit, students know that economic considerations Adapt the ideas to meet your students’ needs. • Solvay process, diaphragm cell determine what commercial processes commonly exist and where, and that For consolidation activities, look at the scheme of • Ellingham diagrams, Gibbs free energy work for Grade 10A and earlier units in economic advantages of such processes must be balanced against environmental threats. • feedstock Grade 12A. • economic advantages, environmental threat You can also supplement the activities with Students who progress further are able to interpret Ellingham diagrams. appropriate tasks and exercises from your school’s textbooks and other resources. Introduce the unit to students by summarising what they will learn and how this will build on earlier work. Review the unit at the end, drawing out the main learning points, links to other work and real world applications.
495 | Qatar science scheme of work | Grade 12 advanced | Unit 12AC.7 | Chemistry 7 © Education Institute 2005 Standards for the unit Unit 12AC.7
SUPPORTING STANDARDS CORE STANDARDS EXTENSION STANDARDS 7 hours Grade 12 standards
2 hours 10A.18.5 Explain, including the electrode 12A.18.1 Know the essential chemistry of the two main processes for producing reactions, industrial electrolytic alkali: the Solvay process and the diaphragm cell. Know the products of Alkali processes such as: these processes and the uses to which they are put, and understand the manufacture • the electrolysis of brine using a economic impact on the processes of the demand for chlorine.
diaphragm cell; … 2 hours 10A.18.8 Describe, with essential chemical 12A.18.2 Analyse Ellingham diagrams to provide information about the feasibility of Extracting metals reactions, the extraction of pig iron the reduction of metal oxides by carbon at different temperatures. from iron ore in the blast furnace and its subsequent conversion into steel 1 hour in the basic oxygen furnace. The oil industry 10A.18.3 Know how a variety of fuels and 12A.18.3 Recognise that Qatar natural gas can act as both a fuel and a feedstock for in Qatar other useful compounds can be industrial processes and that a wide variety of industrial processes are
obtained from petroleum and natural arising in the country that take advantage of the availability of both the gas 2 hours gas. and the products of other processes. Environment versus 10A.18.10 Be aware that large-scale extraction 12A.18.4 Show an understanding of the balance that often has to be made between and refining processes are often the economic advantages that industrial processes bring to Qatar and the economics damaging to the environment and environmental threat that they pose. that this has to be balanced against the benefits of the processes; list some of the steps taken to minimise environmental degradation in the processes studied.
496 | Qatar science scheme of work | Grade 12 advanced | Unit 12AC.7 | Chemistry 7 © Education Institute 2005 Activities Unit 12AC.7
Objectives Possible teaching activities Notes School resources
2 hours Arrange students into pairs. Tell them that, using the Internet or the library, one student from ICT opportunity: Use of the Internet. Use this column to note each pair should research the Solvay process and the other the diaphragm cell. Ask all students your own school’s Alkali manufacture Enquiry skill 12A.2.2 to prepare a 5-minute presentation on: resources, e.g. Know the essential chemistry • the actual process they have researched; textbooks, worksheets. of the two main processes for • the products of these processes; producing alkali: the Solvay process and the diaphragm • the uses to which they are put; cell. Know the products of • the economic impact on the processes of the demand for chlorine. these processes and the Let students give their presentations to their partners and ask them to produce a short set of uses to which they are put, notes summarising their findings. and understand the economic impact on the processes of the demand for chlorine.
2 hours Revise Gibbs free energy by asking a series of quick questions and getting students to write their answers on white boards so that they can hold them up for you to see. Use their Extracting metals responses to determine how much detail to go into for the revision. Analyse Ellingham diagrams Give students data to determine ∆G for the same reaction at two different temperatures, where to provide information about ∆G is positive for one temperature and negative for the other (e.g. the thermal decomposition of the feasibility of the reduction zinc carbonate at 298 K and 573 K. Discuss with the whole group why increasing the of metal oxides by carbon at temperature has this effect. different temperatures. Explain to the whole class how Ellingham diagrams work and how they are plotted. Work through one example with students (e.g. to determine the temperature at which carbon monoxide can be used to obtain zinc from zinc oxide). Provide students with their own copy of an Ellingham diagram and a number of questions to answer. Then tell students to work individually and mark each other’s work.
1 hour Organise students into small groups and ask them to use the Internet or the library to research ICT opportunity: Use of the Internet. the evolution of industries in Qatar that arise from the presence of the gas field. Tell students to The oil industry in Qatar Enquiry skill 12A.2.2 pay particular attention to interdependence of the industries; that is, the way that each industry
Recognise that Qatar natural exploits the products and by-products of others. Tell each group to produce a poster that can be gas can act as both a fuel displayed as part of a poster conference for a target audience (e.g. Grade 11 students, science and a feedstock for industrial teachers or parents). processes and that a wide variety of industrial processes are arising in the country that take advantage of the availability of both the gas and the products of other processes.
497 | Qatar science scheme of work | Grade 12 advanced | Unit 12AC.7 | Chemistry 7 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
2 hours Invite speakers from local industries and environmental agencies, such as Friends of the Visit opportunity: Visit a local industrial plant. Environment, to discuss the balance that often has to be made between the economic Environment versus Enquiry skills 12A.1.6, 12A.1.8, 12A.2.2, 12A.2.3 advantages that industrial processes bring to Qatar and the environmental threat that they economics pose. Show an understanding of Arrange a visit to one of the industries covered in the discussion. the balance that often has to be made between the economic advantages that industrial processes bring to Qatar and the environmental threat that they pose.
498 | Qatar science scheme of work | Grade 12 advanced | Unit 12AC.7 | Chemistry 7 © Education Institute 2005 Assessment Unit 12AC.7
Examples of assessment tasks and questions Notes School resources
Assessment Compare and contrast the Solvay process and diaphragm membrane method for the production Set up activities that allow of alkalis. Discuss the economic impact on the processes of the demand for chlorine. students to demonstrate what they have learned in this unit. Using an example of your choice, write an account demonstrating an understanding of the The activities can be provided balance that often has to be made between the economic advantages that industrial processes informally or formally during bring to Qatar and the environmental threat that they pose. and at the end of the unit, or for homework. They can be selected from the teaching If you were running a factory in which carbon was used to reduce magnesium oxide, would Provide students with a copy of an Ellingham activities or can be new carbon dioxide or carbon monoxide be produced? Estimate the minimum temperature at which diagram. experiences. Choose tasks the reaction would take place. What would be the state of the magnesium at this temperature? and questions from the Given that the whole point of your factory is to produce magnesium, what problems do you face examples to incorporate in in collecting the magnesium as a solid? the activities. From P. Matthews, 1999, Advanced Chemistry 1, Cambridge University Press, p.297
499 | Qatar science scheme of work | Grade 12 advanced | Unit 12AC.7 | Chemistry 7 © Education Institute 2005
500 | Qatar science scheme of work | Grade 12 advanced | Unit 12AC.7 | Chemistry 7 © Education Institute 2005 GRADE 12A: Chemistry 8 UNIT 12AC.8 8 hours Macromolecules
About this unit Previous learning Resources
This unit is the eighth of eight units on chemistry To meet the expectations of this unit, students should already know the The main resources needed for this unit are: for Grade 12 advanced. characteristic structures of natural and artificial addition and condensation • ‘ball and stick’ model kits The unit is designed to guide your planning and polymers. • aspartame, reflux equipment, hydrochloric acid (4 mol dm–3), apparatus for
teaching of chemistry lessons. It provides a link paper chromatography, aspartic acid solution, phenylaniline solution, between the standards for science and your Expectations ninhydrin in butan-1-ol, butan-1-ol, glacial ethanoic acid lesson plans. • egg white, 2 mol dm–3 hydrochloric acid, 1 mol dm–3 sodium hydroxide The teaching and learning activities should help By the end of the unit, students know how addition and condensation solution you to plan the content and pace of lessons. polymers are formed and how their properties can be modified by additives. • 3D model of DNA Adapt the ideas to meet your students’ needs. Students who progress further understand the role of DNA as a genetic • data for isotopic labelling during DNA replication For consolidation activities, look at the scheme of repository and appreciate its crucial role in protein synthesis. • video of DNA replication work for Grade 11A. • video of protein synthesis You can also supplement the activities with • diagrams of two different sections of DNA, listing the order in which the appropriate tasks and exercises from your base pairs exist, table of the triplet base code used in mRNA school’s textbooks and other resources. • samples of HDPE, LDPE and polypropylene Introduce the unit to students by summarising • methyl benzene, 1,1,1 trichloroethane, polystyrene, urea-methanal resin, what they will learn and how this builds on earlier vulcanised natural rubber work. Review the unit at the end, drawing out the • Internet access main learning points, links to other work and real world applications. Key vocabulary and technical terms
Students should understand, use and spell correctly: • peptide bonds, amide, condensation, hydrolysis, electrophoresis, ion- exchange chromatography • hydrogen bonding, disulfide bridges, denaturing • nucleotides, nucleic acids, DNA, RNA, base pairing • triplet code, mRNA, protein synthesis • monosaccharides, polysaccharides, starch, cellulose • additives
501 | Qatar science scheme of work | Grade 12 foundation | Unit 12AC.8 | Chemistry 8 © Education Institute 2005 Standards for the unit Unit 12AC.8
SUPPORTING STANDARDS CORE STANDARDS EXTENSION STANDARDS 8 hours Grade 12 standards
2 hours 11A.25.3 Know that living things produce many 12A.24.1 Know that proteins are formed from combinations of 20 different amino natural condensation polymers, such acids through peptide bonds and that they have a variety of functions in Proteins as proteins from amino acids, starch living things. Know that they can be broken down by hydrolysis into their
and cellulose from glucose, and DNA constituent amino acids, which can be separated by electrophoresis and 3 hours from nucleic acids. ion-exchange chromatography.
Protein synthesis 12A.24.2 Understand the importance of the shape of the protein molecule and the importance of hydrogen bonding and disulfide bridges in maintaining the 1 hour shape; know that heating or treating with acid can destroy the shape (denaturing). Mono- and 12A.24.3 Describe, in simple terms, the structure of nucleotides and nucleic acids. polysaccharides Describe the differences between DNA and RNA molecules, including the
concept of base pairing and the part played by hydrogen bonding. 2 hours 12A.24.4 Understand how DNA can replicate itself and understand its role as the Polymers and repository of genetic information, including the triplet code, and describe structure the function of mRNA in protein synthesis.
11A.25.3 Know that living things produce many 12A.24.5 Describe the structural features of monosaccharides and know that they natural condensation polymers, such form polysaccharides such as starch and cellulose. as proteins from amino acids, starch and cellulose from glucose, and DNA from nucleic acids.
12A.24.6 Describe how the properties of polymers, both natural and synthetic, depend on their structural features, such as the extent of branching and the linkages between chains.
12A.24.7 Know that the properties of polymers can be modified by the use of additives.
502 | Qatar science scheme of work | Grade 12 foundation | Unit 12AC.8 | Chemistry 8 © Education Institute 2005 Activities Unit 12AC.8
Objectives Possible teaching activities Notes School resources
2 hours Give the class the general structure of an amino acid and ask them to identify the two functional Use this column to note groups (i.e. amine and carboxylic acid). Give them a list of the 20 amino acids used to make up your own school’s Proteins proteins. Ask each student to build a ‘ball and stick’ model of two amino acids and join them resources, e.g.
Know that proteins are together by elimination of a water molecule. Explain to the class the definition of a condensation textbooks, worksheets. formed from combinations of reaction and a peptide bond, linking it to the work done in Grade 11 on nylons. Allow the whole 20 different amino acids class to join all their amino acid molecules together to form a protein. Explain how the order in through peptide bonds and which the different R groups occur in the molecule will determine which protein is formed. that they have a variety of functions in living things. Ask students to work in pairs to reflux a sample of aspartame (e.g. Candarel) in hydrochloric Safety: Ninhydrin is harmful and flammable, use Know that they can be acid. They can carry this work out as an investigation to determine the optimum time and in a fume cupboard and wear gloves. Ethanoic broken down by hydrolysis conditions to carry out the hydrolysis. Tell them to follow the progress of the reaction using acid and hydrochloric acid are corrosive. Butan- into their constituent amino paper chromatography, standard solutions of aspartic acid and phenylaniline. Glacial ethanoic 1-ol is flammable and harmful. acids, which can be acid and butan-1-ol can be used as a solvent for the chromatography and ninhydrin in butan-1- Enquiry skills 12A.4.1, 12A.4.2 separated by electrophoresis ol can be used as a locating agent. Ask students to write structural formulae for the organic and ion-exchange reactants and products. chromatography. Ask students to use the Internet or library to research and produce an account of ICT opportunity: Use of the Internet. Understand the importance electrophoresis and ion-exchange chromatography. of the shape of the protein Ask students, individually, to download 3D diagrams of some key proteins (e.g. insulin) from the ICT opportunity: Use of the Internet. molecule and the importance Internet. Ask them to print copies and mark areas where the structure is maintained by Enquiry skill 12A.1.8 of hydrogen bonding and hydrogen bonding, disulfide bridges and ionic interactions. Give students the structures of the disulfide bridges in 20 amino acids used to make naturally occurring proteins. Ask them to classify these into maintaining the shape; know groups responsible for the different types of bonding used to maintain protein shape (e.g. those that heating or treating with with non-polar R groups, those with ionisable R groups, those with polar R groups and those acid can destroy the shape with sulfur in the R group). (denaturing). Ask students to work in pairs to investigate the effect of heat, acids and alkalis on egg white. Bring the individual results together as a whole class and, through question and answer, draw out an understanding of what is occurring when an enzyme is denatured.
503 | Qatar science scheme of work | Grade 12 foundation | Unit 12AC.8 | Chemistry 8 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
3 hours Provide students with unlabelled diagrams of DNA and RNA. Present to them a description of Protein synthesis the similarities and differences between the two molecules. Ask them to annotate the diagrams. Give them diagrams of the bases in DNA and RNA and ask them to build ‘ball and stick’ models Describe, in simple terms, the of them, in order to appreciate base pairing in DNA. Show students a 3D model of DNA. structure of nucleotides and nucleic acids. Describe the Encourage students to use the Internet or library to research the events leading up to the ICT opportunity: Use of the Internet. differences between DNA discovery of the structure of DNA, showing the different ways in which scientists work towards Enquiry skills 12A.2.3–12A.2.5 and RNA molecules, major discoveries. Get them to work in pairs to make a poster of their findings. including the concept of base Discuss with students the role of DNA as the repository of genetic information and the need for Enquiry skill 12A.1.8 pairing and the part played by DNA to replicate. Present students with data from the work of Meselson and Stahl and ask hydrogen bonding. them to work in pairs to discuss and interpret the results. This will allow them to understand the Understand how DNA can nature of semi-conservative replication. Then let them watch a video of DNA replication. replicate itself and With the aid of models, get students to go through the stages of protein synthesis. Ask how understand its role as the many base pairs are needed to represent 20 amino acids. Introduce the idea of triplet coding. repository of genetic Again using models, talk students through the production of mRNA and how it is used in the information, including the ribosomes as a blueprint for different tRNA molecules to line up in the correct sequence. Give triplet code, and describe the students diagrams of two different sections of DNA, listing the order in which the base pairs function of mRNA in protein exist; also provide the triplet base code used in mRNA. Ask students to pair up and get each synthesis. student to work on one of the diagrams to determine the order of amino acids this section of DNA codes for; then ask them to explain to their partner how they worked this out. Let students watch a video on protein synthesis.
1 hour Ask each student to make a model of the same monosaccharide molecule (glucose) and then link them together to make a class molecule of starch. Give students information on their Mono- and properties (e.g. solubility in water, melting point) and ask them to work in pairs to discuss why polysaccharides these properties are different. Complete with a whole class discussion. Describe the structural Repeat the exercise, but this time get students to make a section of cellulose. features of monosaccharides and know that they form Students may wish to download 3D structures from the Internet. ICT opportunity: Use of the Internet. polysaccharides such as starch and cellulose.
2 hours Provide students with samples of different types of poly(ethene) (e.g. high-density poly(ethene) Safety: Products from burning plastics can be and low density poly(ethene)) and polypropylene. Ask them to use textbooks or the Internet to toxic; work in a fume cupboard. Methyl benzene Polymers and structure research the difference in structure of these polymers and then experimentally investigate and and 1,1,1 trichloroethane are flammable – keep Describe how the properties research their properties (e.g. tensile strength, melting point, flexibility). them away from naked flames. of polymers, both natural and Encourage students to investigate the effect of heat, methyl benzene and 1,1,1 trichloroethane on ICT opportunity: Use of the Internet. synthetic, depend on their polystyrene (a linear polymer with no cross-linking), urea-methanal resin (a highly cross-linked structural features, such as Enquiry skill 12A.4.1 polymer) and vulcanised natural rubber (a moderately cross-linked polymer). the extent of branching and the linkages between chains. Ask students to discuss their findings in small groups of three or four and ask each group to produce a table linking structural features to physical properties. Know that the properties of polymers can be modified by Ask students to research the use of plasticisers (e.g. the use of plasticisers in PVA film for the use of additives. wrapping foodstuffs and the possible health implications). Let them debate, in small groups, the role of and need for plasticisers.
504 | Qatar science scheme of work | Grade 12 foundation | Unit 12AC.8 | Chemistry 8 © Education Institute 2005 Assessment Unit 12AC.8
Examples of assessment tasks and questions Notes School resources
Assessment Write an account to describe the structural features of monosaccharides and explain how they Set up activities that allow form polysaccharides such as starch and cellulose students to demonstrate what Read through the following account of DNA and protein synthesis, then write the most they have learned in this unit. appropriate word or words in the gaps to complete the account The activities can be provided The DNA molecule is composed of ______, sugar, phosphoric acid and four types of informally or formally during ______base. Within the molecule the bases are arranged in pairs held together by and at the end of the unit, or ______bonds. For example, adenine is paired with ______. Adenine and for homework. They can be guanine are examples of a group of bases known as ______. The two strands of selected from the teaching nucleotides are twisted around each other to form a double ______and in each turn of activities or can be new the spiral there are ______base pairs. The DNA controls the protein synthesis by the experiences. Choose tasks formation of a template known as ______. Compared with DNA, the sugar component and questions from the of this template is ______, the base ______occurs instead of ______and examples to incorporate in the molecule consists of a ______chain of nucleotides. The template is stored the activities. temporarily in the ______, before passing out into the cytoplasm of the cell. It becomes associated with organelles called ______, which supply the ______required for protein synthesis. Transfer RNA molecules, each with an attached ______, are lined up on the surface of the template according to their ______of ______bases. The amino acids are joined in a chain by ______links to form a polypeptide chain.
Biology examination question, Paper 1, No. 1, London Board, June 1985, in G, Toole and S. Toole, 1991, Understanding Biology for Advanced Level, 2nd edn, Nelson Thornes
Discuss how the extent of branching and the linkages between chains alter the properties of polymers.
505 | Qatar science scheme of work | Grade 12 foundation | Unit 12AC.8 | Chemistry 8 © Education Institute 2005
506 | Qatar science scheme of work | Grade 12 foundation | Unit 12AC.8 | Chemistry 8 © Education Institute 2005 GRADE 12A: Physics 1 UNIT 12AP.1 10 hours Gravity and circular motion
About this unit Previous learning Resources
This unit is the first of seven units on physics for To meet the expectations of this unit, students should already know and be The main resources needed for this unit are: Grade 12 advanced. able to use Newton’s law of motion, and distinguish between mass and • friction-free table and pucks The unit is designed to guide your planning and weight. They should know that the weight of a body may be taken as acting • rubber bungs, string, short pieces of glass tubing, metal washers at a single point known as its centre of gravity. They should be able to recall, teaching of physics lessons. It provides a link and/or between the standards for science and your derive and apply formulae for kinetic and potential energy. • trolley mounted on turntable driven by variable-speed electric motor lesson plans. • apparatus for determining g by free fall The teaching and learning activities should help Expectations • Internet access you to plan the content and pace of lessons. By the end of the unit, students treat problems in circular motion Adapt the ideas to meet your students’ needs. For consolidation activities, look at the scheme of mathematically. They understand the law of universal gravitation and use it Key vocabulary and technical terms work for Grade 11A. to solve problems of motion under gravity. Students should understand, use and spell correctly: Students who progress further understand geostationary orbits and can You can also supplement the activities with derive and use expressions relating to the energy of an orbiting satellite. • terms relating to circular motion: centripetal force, centripetal acceleration, appropriate tasks and exercises from your angular displacement, angular velocity, angular frequency, period school’s textbooks and other resources. • terms relating to gravitational force and field: gravitational field strength, Introduce the unit to students by summarising universal gravitation, inverse-square law what they will learn and how this builds on earlier • terms relating to orbits; satellite, geostationary orbit work. Review the unit at the end, drawing out the main learning points, links to other work and real world applications.
507 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.1 | Physics 1 © Education Institute 2005 Standards for the unit Unit 12AP.1
SUPPORTING STANDARDS CORE STANDARDS EXTENSION STANDARDS 10 hours Grade 12 standards
4 hours 11A.26.1 State Newton’s laws of motion and 12A.25.1 Express angular displacement in radians and describe, qualitatively and apply them to real situations. quantitatively, motion in a circular path due to a perpendicular force Circular motion causing a centripetal acceleration.
11A.26.2 ... Understand and use the 12A.25.2 Understand and use the concept of angular velocity to solve problems in 3 hours relationship F = ma. various situations using the formulae v = rω, a = rω2 and a = v2 ⁄ r. Gravitational force and field 11A.26.4 Distinguish between mass and 12A.25.3 Understand and use the concept of a gravitational field as an example of a
weight. force field and define gravitational field strength as force per unit mass. 3 hours
Orbits 11A.26.6 Know that the weight of a body may 12A.25.4 Recall and use Newton’s law of universal gravitation in the form 2 be taken as acting at a single point F = G(m1m2) ⁄ r and relationships derived from it. known as its centre of gravity.
12A.25.5 Relate gravitational force to the centripetal acceleration it causes, with particular reference to Earth satellite orbits, and show an understanding of the applications of geostationary orbits.
11A.27.3 Recall, derive and apply the formulae 12A.25.6 Derive and use expressions relating the kinetic, potential and total energy 1 2 Ek = ⁄2 mv and Ep = mgh. of an orbiting satellite.
508 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.1 | Physics 1 © Education Institute 2005 Activities Unit 12AP.1
Objectives Possible teaching activities Notes School resources
4 hours Changing direction Use this column to note your own school’s Circular motion Set up a friction-free table and show students the motion of a puck: given a gentle tap, it moves Use a spirit level to ensure that the table is in a straight line at constant speed as described by Newton’s first law of motion. Ask students to horizontal. resources, e.g. Express angular textbooks, worksheets. displacement in radians and suggest how the puck can be made to move in a curved path. They will probably suggest Suitable examples for identifying centripetal pushing it along a curve then releasing it and/or spinning the puck. Show that neither of these describe, qualitatively and force include: suggestions works. By suitable questioning, remind students that a change of direction entails a quantitatively, motion in a • an object being whirled around on the end of change of velocity, hence an acceleration, which requires the action of a resultant force as circular path due to a a string (tension in the string); described by Newton’s second law of motion. perpendicular force causing a • a planet in (almost) circular orbit around the centripetal acceleration. Demonstrate how a force can cause the puck to change direction without changing speed. This Sun (gravitational attraction between Sun and Understand and use the can be done either by a series of gentle taps at right-angles to the direction of motion or by planet); tethering the puck to a fixed point so that the tension in the string provides a force. Show that concept of angular velocity to • a hammer being swung by an athlete prior to when the force stops acting, the puck moves in a straight line along a tangent to the curve. solve problems in various release (tension in the athlete’s arms); situations using the formulae Introduce the term centripetal force. Establish that in any case of circular motion there must be • a car driving round a bend (a combination of 2 2 v = rω, a = rω and a = v ⁄ r. a centripetal force acting. Present some pictures or actual examples of objects in circular motion friction and the car–road reaction force). and ask students to identity the source of the centripetal force.
Students will probably raise the question of centrifugal force (e.g. the sensation of being ‘flung outwards’ when in a vehicle going round a sharp bend at high speed). Explain that this sensation arises only because we feel the inward (centripetal) force from the side of the vehicle as we are pushed into a curved path: there is no outward force acting.
Angular motion On the board or OHP, introduce and define the terms needed to describe angular motion Mathematics: A knowledge of angles measured quantitatively: angular displacement, angular velocity, period, angular frequency. Establish that in radians is required. angular displacements are generally expressed in radians rather than degrees, as the radian is a ‘natural’ measure of angle based on the radius and arc length of a curve. Show that the relationships between angular velocity, displacement and time have exactly the same form as those used to describe linear velocity and displacement. Divide the class into teams. Hand out a sheet containing several short simple examples using Prepare student worksheets. equations of angular motion and conversions between radians and degrees. Challenge each team to complete these correctly in the shortest possible time.
509 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.1 | Physics 1 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
Centripetal force and acceleration Display a large labelled diagram (like the one shown here) on the board or OHP, and use it to show how to derive an expression for the centripetal force by considering the relationship between a small angular displacement ∆θ and the corresponding change in linear velocity ∆v: ∆v = v∆θ. Introduce the term centripetal acceleration and show that the centripetal acceleration a = ∆v ⁄ ∆t = v∆θ ⁄ ∆t = vω = v2 ⁄ r = rω2. Ask students to suggest an expression for the centripetal force F required to produce a given centripetal acceleration: F = ma = mv2⁄r = mrω2. Discuss the SI units of the quantities involved. Establish that, as the radian has units length÷length, the units of angular velocity are equivalent to just s–1.
Mathematics: A knowledge of angles measured in radians, and the small angle approximation, is required. This activity also relates to Standards 10A.25.1 and 10A.25.4. Ask students to work in pairs or small groups to measure the centripetal force F required to 2 produce circular motion. Tell them also to calculate mv ⁄ r and account for any discrepancy between this and the measured value of F: this can generally be attributed to friction in the apparatus. One possible example involves whirling a rubber bung on the end of a string. The string passes Safety: Ensure that students stand well clear of through a short length (about 10 cm) of glass tubing and the other end is tied to some metal whirling bungs.
washers. Students decide on a radius (e.g. 50 cm) and mark the string at this distance from the Enquiry skills 12A.1.1, 12A.1.3, 12A.1.5, bung. One student holds the tube so that the string can slide freely, swings the bung into a 12A.3.3, 12A.4.1, 12A.4.2 circular path and adjusts the rate of whirling so that the mark is close to the top of the tube. Other students time the revolutions in order to determine v. The weight of the washers provides a tension in the string and hence the centripetal force. Another example uses a small trolley mounted on a section of model rail track along a diameter of a turntable rotated by a variable-speed electric motor. The trolley is tethered to a spring that pulls it towards the centre of the turntable. Students adjust the motor speed so that the centre of the trolley lies above a marked position on the track. They time the revolutions. With the motor switched off, they use a forcemeter to find the force exerted by the extended spring: this is the centripetal force. Provide plenty of algebraic and numerical examples that allow students to practise using expressions involving centripetal force and acceleration.
510 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.1 | Physics 1 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
3 hours Gravitational field Gravitational force and Use a question and answer session or class discussion to introduce key ideas about This activity also relates to Standard 10A.25.1 field gravitational fields. Begin by demonstrating one of the methods students encountered in Grade and 10A.25.3. 10 to determine the acceleration due to gravity. Confirm that (provided air resistance is Understand and use the negligible) all objects in free fall close to the Earth’s surface have the same acceleration: concept of a gravitational field g = 9.81 m s--2. as an example of a force field and define gravitational field Introduce the term gravitational field and define gravitational field strength as force per unit --1 strength as force per unit mass. Establish that the field strength close to Earth’s surface is 9.81 N kg , and that this is mass. necessarily the same as the gravitational acceleration so the symbol g is used. Discuss the SI units of g and ask students to show that 1 m s--2 = 1 N kg--1. Relate gravitational force to the centripetal acceleration it Universal gravitation causes ... Continuing the discussion from above, remind students of work in Grade 10 where they learned Recall and use Newton’s law that an object’s weight can vary with its location (e.g. objects weigh less on the Moon than on of universal gravitation in the Earth). Ask them to suggest what factors, in addition to an object’s own mass, might influence 2 form F = G(m1m2) ⁄ r and the gravitational force it experiences. It will be helpful to remind students that, as described by relationships derived from it. Newton’s third law of motion, this force arises from an interaction between two objects (e.g. the object and the Earth). With suitable prompting, students should be able to suggest that the force must depend on the masses of both interacting objects, i.e. F ∝ m1m2.
Students might also be able to suggest that the force may depend on the separation of the two Data: objects. To illustrate that this must be the case, ask students to work in pairs through the • orbital period of moon = 27.3 days following exercises. • orbital radius of moon = 3.84 × 108 m What is the Moon’s centripetal acceleration in its near-circular orbit around the Earth? • Earth’s radius = 6.38 × 106 m What is the strength of the Earth’s gravitational field at the distance of the Moon? The orbital period will need to be expressed in –2 How does this compare with the gravitational force per unit mass at the Earth’s surface? seconds in order to get an acceleration in m s . Discuss how the force must depend on distance. Students might suggest that there is an Enquiry skills 12A.2.1, 12A.2.2, 12A.2.5 inverse proportionality. Use results from the exercise above to illustrate that the force varies as This activity also relates to Standard 10A.25.1. the inverse-square of the distance between the centres of the two interacting objects, i.e. gravitational force and field strength obey an inverse-square law. Establish that the force can be described mathematically by Newton’s law of universal 2 gravitation, expressed mathematically as F = Gm1m2 ⁄ r , where G is the universal gravitational constant whose value has been determined by direct measurements of the force between two objects of known mass. Point out that the above discussion is very similar to that used by Isaac Newton in formulating his law, and that Newton’s approach was revolutionary because it extended terrestrial physics to ‘heavenly bodies’, which were at the time believed to be governed by different laws. Provide plenty of algebraic and numerical examples involving universal gravitation. Ask students to use library and Internet resources to research historical and modern methods of ICT opportunity: Use of the Internet. determining G (which is the least precisely known of all the fundamental constants). Each Enquiry skills 12A.1.6, 12A.1.8, 12A.2.1 student should produce a written account of one method, including a bibliography listing the sources consulted.
511 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.1 | Physics 1 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
3 hours Satellites Orbits Establish that a satellite is any object in orbit around a planet, and that satellites can be natural (moons) or artificial. Hold a short brainstorming session in which you ask students to think of Relate gravitational force to uses for artificial satellites. List these on the board or OHP. They might include: the centripetal acceleration it causes, with particular • communications;
reference to Earth satellite • weather forecasting;
orbits, and show an • military intelligence; understanding of the • astronomical telescopes;
applications of geostationary • land surveying; orbits. • satellite navigation for drivers, walkers and explorers. Derive and use expressions Establish that, for some of these applications, a satellite should move relative to the Earth’s relating the kinetic, potential surface, but for others (e.g. communications) it is desirable that the orbit is geostationary. and total energy of an orbiting satellite. Discuss how satellites are launched and establish that, in principle, this involves using a rocket to take the satellite to the desired height, then ejecting it horizontally at exactly the right speed to maintain an orbit. Ask students to suggest how this speed might be calculated: knowing the orbital radius r and way that gravitational field g varies with distance, for a circular orbit speed v must satisfy g = v2 ⁄ r. Ask students to calculate the speed and orbital period of a near-Earth satellite, such as the space shuttle. They will need to know the Earth’s radius (given above) and use g = 9.81 N kg–1. Challenge students, working in pairs, to derive an algebraic expression for the radius of a geostationary orbit and hence for the height above Earth’s surface. (Before they start, establish that the period must be 24 hours.) Then work through this derivation on the board or OHP. Encourage students to download and use applets that illustrate how a satellite’s launch speed ICT opportunity: Use of the Internet and Java affects its orbit: if the launch speed is higher than that required for circular orbit, the satellite applets. goes into elliptical orbit or might escape and never return; too low a speed also results in elliptical orbit, which in this case might intercept and crash into the Earth’s surface. Point out that measurements of orbits provide us with the most reliable method of determining masses of planets and stars: knowing the size and period of an orbit allows the mass of the orbited object to be determined. Provide examples that allow students to practise using relationships and data relating to orbits.
512 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.1 | Physics 1 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
Energy Ask students to imagine that they are working on a satellite launch programme and need to Mathematics: A knowledge of integral calculus calculate the amount of fuel required to raise a space vehicle to a given height and then eject a is highly desirable. satellite at the desired speed. They might suggest calculating the increase in gravitational If students are not familiar with integration, then potential energy of the launch assembly using Ep = mgh and the satellite’s kinetic energy using it is possible to obtain a numerical expression for 2 Ek = ½mv then relating the total to the energy released when fuel is burned. Discuss the the change in Ep in an inverse-square law field limitations of this approach: for anything other than a near-Earth orbit, the value of g changes by drawing a graph of F against r and finding the significantly with height, so the simple expression E = mgh cannot be used. area beneath it by counting squares. Show how gravitational potential energy can be defined and calculated in an inverse-square law Alternatively, simply present the expression
field. If students are familiar with calculus, show how the expression dE = Fdr with Ep = –Gm1m2 ⁄ r and discuss its meaning and 2 F = –Gm1m2 ⁄ r can be integrated between limits r1 and r2. Explain the sign convention: if r is application.
measured outwards from the Earth’s centre, then F acts in the opposite direction so is negative. Explain that it is convenient to define the zero of gravitational potential energy at r = ∞, which
leads to the expression Ep = –Gm1m2 ⁄ r for the gravitational potential energy of two masses separated by a distance r. This energy is always negative as, when two objects ‘fall’ towards each other, there is a loss of gravitational potential energy. It is much more straightforward to find an expression for kinetic energy of an orbiting object and you could ask students to derive this for themselves. Using the expression for centripetal force 2 2 (with m1 the mass of the satellite and m2 the mass of the Earth), m1v ⁄ r = Gm1m2 ⁄ r , hence 2 Ek = ½ m1v = Gm1m2 ⁄ 2r.
Ask students to combine the expressions for Ep and Ek to find the total energy of an orbiting
satellite: E = –Gm1m2 ⁄ r + Gm1m2 ⁄ 2r = –Gm1m2 ⁄ 2r. Discuss the interpretation of this expression. Provide some examples that allow students to consolidate their understanding of energy of orbiting satellites. Some of these can be algebraic and numerical but some should require a verbal explanation.
513 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.1 | Physics 1 © Education Institute 2005 Assessment Unit 12AP.1
Examples of assessment tasks and questions Notes School resources
Assessment A road going round a bend is banked so that, at 50 km h–1, the centripetal force is provided only Set up activities that allow by the reaction force that acts at right-angles to the road surface. students to demonstrate what a. Explain the advantage of driving along this section of road at exactly 50 km h–1. they have learned in this unit. b. The road surface is at 15° to the horizontal. What is the radius of the bend? The activities can be provided informally or formally during The Earth takes 1 year to move once around the Sun in a near-circular orbit of radius 11 and at the end of the unit, or 1.50 × 10 m. What is the Earth’s centripetal acceleration? for homework. They can be Two students, each of mass 70 kg, stand 1.5 m apart. Calculate the size of the gravitational selected from the teaching force between them. activities or can be new experiences. Choose tasks Use the following data to calculate the mass of the Earth. and questions from the • Earth’s radius = 3.84 × 108 m examples to incorporate in --1 • Gravitational field at Earth’s surface = 9.81 N kg the activities. • G = 6.67 × 10--11 N m2 kg--2
Derive an algebraic expression for the radius of a geostationary orbit expressed in terms of the Earth’s mass and the universal gravitational constant.
Saturn’s satellite Titan has an orbital radius of 1.22 × 109 m and a period of 1.38 × 106. What is the mass of Saturn? (Use G = 6.67 × 10–11 N m2 kg--2.)
A space vehicle in orbit loses energy because of viscous drag forces as it passes through the outer atmosphere. Explain carefully what happens to its total energy, its gravitational potential energy and its kinetic energy and hence say whether it gains or loses height.
514 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.1 | Physics 1 © Education Institute 2005 GRADE 12A: Physics 2 UNIT 12AP.2 15 hours The nature of matter
About this unit Previous learning Resources
This unit is the second of seven units on physics To meet the expectations of this unit, students should already know that a The main resources needed for this unit are: for Grade 12 advanced. force can cause deformation, and know the relationship between force and a • blocks of upholstery foam The unit is designed to guide your planning and change of momentum. They should understand and use the term pressure. • samples of materials for tensile and shear testing They should be able to describe the kinetic particle model for solids, liquids teaching of physics lessons. It provides a link • large masses and gases, and define a mole of a substance in terms of the Avogadro between the standards for science and your • apparatus for determining Young’s modulus of a wire lesson plans constant. They should define temperature and explain how a temperature scale is constructed. They should be able to recall and use the formula for • air blower The teaching and learning activities should help kinetic energy. • apparatus to show the Bernoulli effect in flowing water you to plan the content and pace of lessons. • simple wind tunnel (or apparatus to construct one using a fan or air- Adapt the ideas to meet your students’ needs. blower) For consolidation activities, look at the scheme of Expectations • apparatus to demonstrate Boyle’s law work for Grade 11A. By the end of the unit, students classify solids according to stiffness, • apparatus to demonstrate Charles’s law You can also supplement the activities with tensile strength, compressive strength and shear strength, plot and interpret • constant volume gas thermometer appropriate tasks and exercises from your stress–strain graphs for different solids and define and use Young’s school’s textbooks and other resources. • Internet access modulus. They know how these properties are used by engineers and Introduce the unit to students by summarising understand the usefulness of composite materials. They explain surface what they will learn and how this builds on earlier tension. They solve problems related to ideal gas behaviour and show Key vocabulary and technical terms work. Review the unit at the end, drawing out the mathematically the relationship between temperature and the kinetic energy Students should understand, use and spell correctly: main learning points, links to other work and real of molecules. world applications. • terms relating to properties of solids: stiffness, stress, strain, strength, Students who progress further explain qualitatively how fluid flow past tensile, compressive, shear, Young’s modulus, composite material solid bodies can give rise to pressure. They explain how the behaviour of • terms relating to fluids: surface tension, adhesion, cohesion, Bernoulli real gases deviates from ideal behaviour at high pressures and low effect temperatures, and derive relationships between the molecular kinetic energy and the pressure, volume and temperature of an ideal gas. • terms relating to gases: ideal gas, Boyle’s law, Charles’s law, absolute temperature, absolute zero, universal gas constant, mean square speed, Boltzmann constant
515 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.2 | Physics 2 © Education Institute 2005 Standards for the unit Unit 12AP.2
SUPPORTING STANDARDS CORE STANDARDS EXTENSION STANDARDS 15 hours Grade 12 standards
6 hours 10A.26.3 Know that a force acting on an object 12A.26.1 Classify solids according to stiffness, tensile strength, compressive can cause deformation ... strength and shear strength. Plot and interpret stress–strain graphs for Properties of different solids. Define and use the concept of Young’s modulus. solids 12A.26.2 Relate the uses of materials to their characteristic behaviour under different types of stress and note the importance of composite materials, both 6 hours natural and synthetic. Ideal and real 12A.26.3 Explain surface tension in terms of interparticle forces. gases
10A.27.7 Understand and use the term 12A.26.4 Explain qualitatively how fluid flow past solid bodies can generate pressure 3 hours pressure... changes in the fluid; give practical examples of this. Fluids 10A.27.1 Describe the kinetic particle model 12A.26.5 Apply the kinetic particle model to an ideal gas and explain, in terms of for solids, liquids and gases, and molecular size and intermolecular forces, how the behaviour of real gases relate the difference in the structures deviates from the ideal model at high pressures and low temperatures. and densities of solids, liquids and gases to the spacing, ordering and motion of particles. 11A19.2 Define a mole of a substance in 12A.26.6 Derive, know and use the gas laws and the general gas equation terms of the Avogadro constant ... PV = nRT and show how the general gas equation leads to a concept of 11A.28.1 Define temperature and explain how absolute zero of temperature. a temperature scale is constructed ... 11A.26.2 Know that ... a momentum change 12A.26.7 Show that a theoretical treatment of molecular movement and gas on a body is equal to the force pressure leads to the relationship pV 1 mNc 2 and hence, by combining = 3 causing it. with the gas equation, that the average kinetic energy of a particle is 11A.27.3 Recall, derive and apply the proportional to its absolute temperature. 1 2 formulae Ek = 2 mv …
516 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.2 | Physics 2 © Education Institute 2005 Activities Unit 12AP.2
Objectives Possible teaching activities Notes School resources
6 hours Choosing materials Use this column to note your own school’s Properties of solids Set up a display of objects made from a wide variety of materials. Ask students to visit each Suitable objects include: cooking utensils, exhibit in turn and make brief notes in which they identify the types of material used (e.g. wood, clothing, footwear, bicycle, sports equipment, resources, e.g. Classify solids according to textbooks, worksheets. stiffness, tensile strength, metal, ceramic, polymer, textile) and suggest why each material was chosen for making that packaging. object. compressive strength and Use pictures if actual objects are unobtainable. shear strength. Plot and After students have explored the display, hold a brainstorming session in which they suggest interpret stress–strain graphs the types of question that a designer or engineer might consider when choosing a material for a for different solid. Define and particular purpose. Questions might include: use the concept of Young’s • Is it waterproof? modulus. • Does it bend easily? Relate the uses of materials • Does it stretch easily? to their characteristic • What does it look like? behaviour under different • How big a force can it withstand without breaking? types of stress and note the • Does its production harm the environment? importance of composite • How dense is it? materials, both natural and synthetic. • How much does it cost? Explain that in this part of the unit most of the attention will be on how materials respond to forces – though many of the other questions suggested are also relevant in practice to the choice of materials. By suitable questioning, find out how much students recall of work in earlier units in which they tested material samples, and remind them of Hooke’s law. Stress and strain Use blocks of upholstery foam to demonstrate how the dimensions of a sample affect the The foam blocks should all be made for the deformation produced by a force. same material (ideally all cut from a single larger First use two blocks of the same height but different cross-sectional area. Place a sheet of stiff block). card on top of each, and the same load on top of each card. Students should observe that the Suitable dimensions for the blocks are: narrower block experiences the greater deformation: if it has half the area of cross-section it • 10 cm × 10 cm × 10 cm; experiences twice the deformation. Increase the load on the wider block so as to produce the • 20 cm × 10 cm × 10 cm; same deformation of each block. Establish that if both blocks have the same load ÷ area, they • 10 cm × 10 cm × 5 cm. experience equal deformation. Arrange the blocks with their largest dimensions Introduce the term stress defined as force ÷ area. Discuss the SI units of stress and establish horizontal, otherwise they may buckle under a that (recalling work on pressure from earlier grades) they can be expressed as N m--2 or Pa. load. Next use two blocks of the same cross-sectional area but different height. As before, give each You will need to experiment beforehand to find the same load. The shorter block experiences a smaller deformation. Establish that suitable loads to produce noticeable deformation deformation ÷ original height is the same for each block. without flattening the blocks. Sets of 100 g
Introduce the term strain defined as change in length ÷ original length. Discuss its units and hanger masses are a good starting point. point out that strain is length ÷ length so has no units. Establish that strain can be expressed as This activity also relates to Standard 10A.25.1. a ratio, a fraction, a decimal number or a percentage.
517 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.2 | Physics 2 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
Ask students what results they would expect if differently shaped samples of a given material were all subject to the same stress (they would each experience the same strain). Ask what they would expect if samples of a second material were also subject to the same stress (the resulting strain would probably differ from that found for the first material). Establish that measuring stress and strain enable the properties of different materials to be compared reliably, even though the samples might have different dimensions. Point out that these examples with the foam blocks involve compressive stress and strain. Provide students with some examples that allow them to practise calculations relating stress to force and area, and relating stress to deformation and original length.
Testing materials Ask students to work in pairs, each using a sample of a different material, to investigate how Suitable materials include: metal wires strain depends on the applied tensile stress. Provide basic apparatus then encourage students (e.g. copper, steel), nylon, polythene. to design and modify their experiments so as to ensure accuracy and precision and to obtain Safety: Goggles should be worn to protect results as efficiently as possible. against injury when samples fail under high Students should obtain and tabulate data for a range of applied loads. They should explore what tension. happens when a load is removed (does the sample return to its original length?) and should, Enquiry skills 12A.1.1, 12A.1.3–12A.1.5, where possible, increase the load until the sample breaks. They should plot a graph to show the 12A.3.1–12A.3.3, 12A.4.1, 12A.4.2 relationship between stress and strain. Photocopy the graphs and distribute to the whole class. This activity also relates to Standard 10A.25.2.
Young’s modulus and breaking stress Discuss the graphs obtained in the previous activity with the whole class and draw attention to This also relates to Standard 10A.25.1 key features. Close to the origin, most graphs will approximate to straight lines, and for some materials this behaviour continues until the sample nears breaking point. Establish that if stress is directly proportional to strain, the material obeys Hooke’s law, which students should recall as a direct proportion between force and extension. Introduce Young’s modulus E = σ ⁄ ε, where σ is stress and ε is strain and establish that it is the gradient of the part of a stress–strain graph where Hooke’s law is obeyed. Discuss the SI units of Young’s modulus and establish that they are the same as the units of stress: N m–2 or Pa. Ask students how they would describe the difference between materials with a small and a large Young’s modulus. A material with large E requires a large stress to produce even a small strain; it is very stiff. The term stiffness is sometimes used loosely in place of Young’s modulus (though it can also be used to mean k in the expression F = kx). If available, show students apparatus specially made to measure Young’s modulus for a metal wire. Point out the features designed to increase accuracy and precision (e.g. Vernier scale). If time allows, let students use this apparatus themselves. Return to the discussion of the graphs. Point out that some samples were tested to destruction, and define the tensile strength or ultimate tensile stress as the maximum stress that a material can withstand before breaking. Provide plenty of algebraic and numerical examples that allow students to practise calculations involving stress, strain and Young’s modulus.
518 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.2 | Physics 2 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
Shear Use foam blocks to demonstrate how a material can be sheared, and define shear stress and Mathematics: A knowledge of angles measured strain. Using a labelled diagram, show that deformation is measured at right-angles to the in radians is required. length of a sample and so (for small deformations) shear strain corresponds to an angle Enquiry skills 12A.1.1–12A.1.5, 12A.3.1– measured in radians. 12A.3.4, 12A.4.1. Ask students to work in pairs or small groups to design and carry out a test to see how a This activity also relates to Standard 10A.25.2. material behaves under shear stress. Tell them to produce a written report of their work explaining how they attempted to ensure accuracy and precision in their measurements. Composites Assign each student, or pair of students, a natural or synthetic composite material (e.g. wood, ICT opportunity: Use of the Internet. concrete, fibreglass resin). Tell them to use the Internet and library resources to research Enquiry skills 12A.1.8, 12A.3.4 information about the material, addressing such questions as: • What is its composition? • What does it look like on a small scale? • How do its properties differ from those of its individual components? • What is it used for? Ask students to produce an informative poster summarising their findings. Hold a conference-style poster session. Display the posters around the room and allow students time to visit one another’s posters and discuss their work.
3 hours Surface tension Fluids Set up a circus of activities illustrating the effects of surface tension. For each, provide brief Suitable examples include: instructions telling students what to do and what to look for. They should visit each in turn and Explain surface tension in • observe the meniscus on water and on mercury; make notes. terms of interparticle forces. • observe water rising up a capillary tube; Introduce and define the term surface tension. Ask students to suggest explanations for their Explain qualitatively how fluid • sprinkle fine power on the surface of water observations in terms of the kinetic particle model. Introduce the terms adhesion and cohesion flow past solid bodies can then add a drop of detergent; to describe the observations. generate pressure changes • blow bubbles using different soap and in the fluid; give practical detergent solutions. examples of this. Fluid flow Carry out a series of demonstrations to show that the flow of a fluid (liquid or gas) gives rise to the Bernoulli effect (i.e. there is a drop in pressure transverse to the flow). Suitable examples include the following. • Each student holds a sheet of A4 paper by one short edge so that it forms a curved surface, then blows gently over it. • Each student holds two sheets of A4 paper by their short edges so that they hang vertically a few centimetres apart, then blows gently between them. • Place a table-tennis ball in a fast-moving air stream from a blower. Tilt the blower and show that the ball remains supported even when the air-stream is almost horizontal.
519 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.2 | Physics 2 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
Use specially designed apparatus to demonstrate the Bernoulli effect. Water flows through a Note that the Bernoulli effect is not primarily horizontal tube with a narrow section. Vertical tubes indicate the transverse pressure, which is responsible for the lift of an aircraft wing. Rather, lowest where the water flows fastest. Relate the difference in pressure (and hence in force) to a downward deflection of air from the lower the change in the water’s velocity as it enters and leaves the narrow section. surface produces an upward force. Ask students to suggest other examples of the Bernoulli effect in operation. Explain how the shape of an aerofoil can help generate lift. If time and apparatus permit, ask students to work in teams to plan and carry out wind-tunnel Enquiry skills 12A.1.1–12A.1.5, 12A.3.1– tests of different aerofoil sections to investigate the lift produced. Ask them to try to predict and 12A.3.4, 12A.4.1, 12A.4.2 explain their results, and to produce a written report of the procedure adopted, apparatus used and results obtained.
6 hours Boyle’s law Ideal and real gases Using specially designed demonstration apparatus, obtain data to show how the volume, V, of a If there is enough apparatus, students should fixed mass of gas depends on its pressure, p. Ask students to plot graphs of p against V, and p work in pairs to obtain their own data. Derive, know and use the gas against 1 ⁄ V. Establish that, for a fixed mass of gas at constant temperature, pV is a constant laws and the general gas equation PV = nRT and show (i.e. Boyle’s law is obeyed). how the general gas equation In practice, the data may deviate from Boyle’s law. Ask students to use the kinetic particle leads to a concept of model to suggest explanations. In order to increase the pressure, a force is applied to the gas absolute zero of temperature. (i.e. work is done) and energy is supplied, so the gas temperature rises and the gas tends to expand. If the gas is allowed to return to room temperature after each change in pressure, then Show that a theoretical deviations from Boyle’s law are reduced. treatment of molecular movement and gas pressure Provide students with some examples that allow them to practise using Boyle’s law in leads to the relationship calculations. pV 1 mNc 2 and hence, by = 3 Absolute temperature combining with the gas Set up and demonstrate apparatus to how the volume of a fixed mass of gas changes with If there is enough apparatus, students should equation, that the average temperature measured in °C. Similarly, use a constant volume gas thermometer to demonstrate work in pairs to obtain their own data. kinetic energy of a particle is how pressure depends on temperature. This activity also relates to Standard 10A.25.1. proportional to its absolute Ask students to plot graphs of volume against temperature, and pressure against temperature, temperature. and establish that the volume and pressure each vary linearly with temperature. Apply the kinetic particle Discuss and show how the graphs can be extrapolated to find the temperature at which p and V model to an ideal gas and become zero. Tell students that this temperature is called absolute zero and is found to be explain, in terms of molecular close to –273 °C. Point out that, in practice, the volume of a gas cannot become zero (its size and intermolecular molecules have finite size), and that real gases condense to liquids before reaching absolute forces, how the behaviour of zero, so the extrapolation strictly applies only ‘ideal’ gases. (However, absolute zero is still a real gases deviates from the meaningful concept and, as will be seen later in this unit, can be understood in terms of ideal model at high pressures molecular kinetic energy.) and low temperatures. Explain how the existence of absolute zero enables a scale of absolute temperature to be
defined. Establish that the SI unit of absolute temperature, T, is the kelvin, K, and that a temperature change of 1 K is exactly equal to a change of 1 °C. Use several quick-fire oral questions to give students practice in converting between temperatures expressed in K and in °C.
520 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.2 | Physics 2 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
Gas laws Refer to the previous activity and ask students to sketch graphs showing how pressure and This activity also relates to Standards 10A.25.1 volume of a fixed mass of gas depend on absolute temperature, T. and 10A.25.3. Introduce Charles’s law: V ∝ T for a fixed mass of gas at constant pressure. Similarly, state the pressure law: p ∝ T for a fixed mass of gas whose volume is constant.
On the board or OHP, show how these two laws can be combined with Boyle’s law to produce
pV ∝ T. Discuss the point that pV must also be proportional to the amount of gas present: doubling the amount will double the volume at a given pressure. But ‘amount’ is a loose term, so explain that, more precisely, the relationship is expressed in terms of the number, n, of moles present. This leads to the ideal gas equation pV = nRT, which defines the value of the universal gas constant, R.
Show students that the SI units of pV are 1 N m–2 × 1 m3 = 1 N m = 1 J. Ask students to deduce
the SI units of R.
Point out that the behaviour of real gases can deviate markedly from that described by the ideal gas equation, particularly when they are close to condensing, but that in solving problems it is often useful to assume ideal behaviour. Provide several examples of algebraic and numerical calculations that allow students to practise using the ideal gas equation.
Molecular behaviour On the board or OHP, show students how the pressure of a gas can be related to the motion of its molecules and hence derive the equation pV = 1 mnc 2. 3 To make this derivation more engaging and interactive, pause frequently and ask students
questions to check that they have understood each step, and questions that anticipate the next step. Start by considering a single molecule mass m travelling at speed c parallel to one edge of a rectangular box of dimensions x × y × z = V and repeatedly making elastic collisions with one face.
Derive expressions for the momentum change at each collision (2mc) and for the time interval
between collisions (2x ⁄ c), and hence expressions for the force exerted on one face (mc2 ⁄ x) and for the pressure exerted on that face (mc2 ⁄ xyz = mc2 ⁄ V). Work through an argument to derive the pressure, p, exerted by N molecules, of which one-third will, on average, be travelling at speed c in each of three perpendicular directions (p = mc2 ⁄ 3V). Explain that, in practice, there will be a range of speeds, so we must use the average value of 2 2 c (i.e. the ‘mean square speed’), represented as c . Show how to combine the final expression with the ideal gas equation to get Nm c 2 ⁄ 3 = nRT.
521 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.2 | Physics 2 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
Show that, as N ⁄ n is equal to the Avogadro number NA (the number of molecules per mole), we To avoid confusion between the number of 2 can write m c ⁄ 3 = RT ⁄ NA = kT, where k (= R ⁄ NA) is the Boltzmann constant. Hence show how moles (e.g. in the ideal gas equation) and the to relate the average molecular kinetic energy Ek to absolute temperature: number of molecules, use N rather than n to
E = 1 mc 2 = 3kT 2 represent the number of molecules. k 2 Establish that this expression allows another interpretation of absolute zero: it is the
temperature at which molecular motion ceases.
Ask students to derive the SI units of k (i.e. J K–1).
Work through some examples of calculations relating molecular kinetic energy to temperature, pressure and density, and give students some numerical and algebraic examples that allow them to practise using the relationships. Real gases Point out to students that all the relationships listed above apply to ideal gases. Establish that in This activity relates to Standard 10A.25.3. such a gas the molecules: • make frequent elastic collisions with each other and the walls of their container;
• exert no forces on one another except while in contact;
• are in contact for a very short time compared with the time between collisions;
• have a very small volume compared with the volume available for them to move in.
Ask students, in small groups, to list differences between real and ideal gas molecules, and suggest how these might affect the equations describing their behaviour. Hold a reporting back session to collect ideas together. The main points are that molecules do exert long-range forces on one another (the van der Waals force) and they occupy a finite volume. These factors become particularly important when the pressure of a gas is high and/or the temperature is low (i.e. it is close to condensing). In practice, a real gas behaves most like an ideal gas when the pressure is low and the temperature high. Students should appreciate that, in solving problems, it is usually convenient to assume ideal gas behaviour. With more advanced students, it might be appropriate to introduce and discuss the van der Waals gas equation.
522 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.2 | Physics 2 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
Understanding particles Ask students, in small groups, to use the Internet and library resources to research historical In addition to, or in place of, the examples developments of theories about particles. Allocate each group a different task and tell them to suggested here, include at least one example prepare a ten-minute PowerPoint presentation (including an aknowledgment of sources relating to Islamic science and scientists. consulted). Suitable tasks include the following. Enquiry skills 12A.1.6, 12A.1.8, 12A.2.1, • The idea that matter is made up of tiny indivisible particles originated with the ancient Greeks. 12A.2.2, 12A.2.4, 12A.2.5, 12A.2.6 Who were the main people famous for recording this idea? How did the ancient Greek ideas
compare with our modern view of atoms?
• Modern ideas about atoms can be traced back to the European scientist John Dalton. When did he live? What were his ideas about atoms? • Even as recently as 1900, many scientists did not believe atoms existed. Albert Einstein carried out some important work that convinced most people that atoms were real. What did he do?
• Scientists today believe that all matter is made up of particles, and that some particles are ‘fundamental’ (cannot be divided further). Which particles are currently believed to be fundamental? When were they discovered? Hold a conference in which each group presents its work to the rest of the class. The presentations should be made in chronological order. Allow time for questions after each presentation. Bring out the point that our understanding of the nature of matter has developed unevenly through history, with the postulation of major theories being followed by long periods of slow development. Some theories are abandoned permanently, whereas others (such as Greek atomic ideas) are discarded then ‘reinvented’. As a follow-up to the conference, discuss with students the apparent contradiction between the random behaviour of the particles believed to make up the Universe, and the deterministic nature of major world religions. First establish some rules of behaviour: students should respect one another’s views, even though they may disagree strongly; in later conversations outside the classroom, views expressed during the discussion must not be attributed to individuals. Then encourage students to express their views and to ask questions of you and one another. Do not attempt to resolve the paradox at this stage; as students will learn in later units, random behaviour can still be described by definite laws.
523 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.2 | Physics 2 © Education Institute 2005 Assessment Unit 12AP.2
Examples of assessment tasks and questions Notes School resources
Assessment A student estimates that the total cross-sectional area of his leg bones is 20 cm2. His mass is
Set up activities that allow 70 kg. What is the stress in his leg bones when he stands on both feet? students to demonstrate what A metal wire of diameter 0.5 mm and length 4.0 m extends by 3.0 mm when the applied tension they have learned in this unit. is 75 N. What is the Young’s modulus of this metal? The activities can be provided informally or formally during Using the terms adhesion and cohesion, and with the help of labelled diagrams, explain why and at the end of the unit, or water rises up a narrow tube whereas mercury does not. for homework. They can be A bubble of gas, diameter 2 mm, is trapped in a container of liquid at normal atmospheric selected from the teaching pressure (1 × 105 Pa) and a temperature of 25 °C. The container is opened on board an aircraft activities or can be new where the temperature is 22 °C and the surrounding pressure is 0.9 × 105 Pa. What is the experiences. Choose tasks diameter of the bubble as it escapes from the liquid? and questions from the examples to incorporate in What is the average kinetic energy of molecules in the air at room temperature 25 °C? At this the activities. temperature, what is the average speed of an oxygen molecule? Use k = 1.38 × 10 J K–1. Mass –27 of oxygen molecule (O2) m = 32 × 1.67 × 10 kg.
524 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.2 | Physics 2 © Education Institute 2005 GRADE 12A: Physics 3 UNIT 12AP.3 11 hours Thermodynamics
About this unit Previous learning Resources
This unit is the third of seven units on physics for To meet the expectations of this unit, students should already be able to The main resources needed for this unit are: Grade 12 advanced. define work and apply the concept of work as the product of a force and • bicycle pumps The unit is designed to guide your planning and displacement in the direction of a force. They should be able to define kinetic • bicycle inner tubes (with valves intact) and potential energy, and describe the principle of energy conservation and teaching of physics lessons. It provides a link • film or video clips showing simple processes running both forwards and in apply it to simple examples. They should know and be able to use the between the standards for science and your reverse lesson plans. general gas equation PV = nRT, and know that this equation leads to a concept of absolute zero of temperature. They should know that the average The teaching and learning activities should help kinetic energy of a particle is proportional to its absolute temperature. Key vocabulary and technical terms you to plan the content and pace of lessons. Adapt the ideas to meet your students’ needs. Students should understand, use and spell correctly: For consolidation activities, look at the scheme of Expectations • terms relating to energy and temperature: absolute zero, absolute work for Grade 11A. temperature By the end of the unit, students understand the concept of absolute zero You can also supplement the activities with of temperature and can relate changes in internal energy, heat changes and • terms relating to the first law of thermodynamics: thermodynamic system, appropriate tasks and exercises from your work done on a thermodynamic system. They relate entropy to disorder and work, internal energy, adiabatic, isothermal school’s textbooks and other resources. describe the second law of thermodynamics, and its consequences in terms • terms relating to the second law of thermodynamics: entropy, irreversible Introduce the unit to students by summarising of entropy. process, reversible process, heat engine, heat source, heat sink what they will learn and how this builds on earlier Students who progress further calculate work done by a gas expanding work. Review the unit at the end, drawing out the against constant pressure, and understand internal energy in terms of the main learning points, links to other work and real energies of molecules. They know that the second law of thermodynamics world applications. imposes limits on the efficiency of any heat engine.
525 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.3 | Physics 3 © Education Institute 2005 Standards for the unit Unit 12AP.3
SUPPORTING STANDARDS CORE STANDARDS EXTENSION STANDARDS 11 hours Grade 12A standards
1 hour 12A.26.6 ... show how the general gas 12A.27.1 Show an understanding, in terms of particle energy, of the concept of equation leads to a concept of absolute zero and the absolute scale of temperature, which does not Energy and absolute zero of temperature. depend on the property of any particular substance. Convert temperatures temperature measured in kelvin to degrees Celsius.
12A.26.7 Show that ... the average kinetic 12A.27.2 Recognise that temperature is a measure of the average kinetic energy of 6 hours energy of a particle is proportional to molecules of a substance. The first law of its absolute temperature. thermodynamics 11A.27.2 … Describe the principle of energy 12A.27.3 Recognise that the first law of thermodynamics is a statement of the
conservation and apply it to simple principle of conservation of energy. 4 hours examples. The second 12A.26.6 Derive, know and use the gas laws 12A.27.4 Explain what is meant by a thermodynamic system and describe the law of and the general gas equation concepts of heat, work and internal energy in the case of an ideal gas. thermodynamics PV = nRT ... 12A.27.5 Use the first law of thermodynamics relating changes in internal energy, heat changes in the system and work done on the system.
11A.27.1 Define work and apply the concept of 12A.27.6 Calculate work done by a gas expanding against a constant external work as the product of a force and pressure using W = p∆V. displacement in the direction of a force.
11A.27.2 Define kinetic and potential 12A.27.7 Know that internal energy is determined by the state of the system and that energy … it can be expressed as the sum of the kinetic and potential energies associated with the molecules of a system.
12A.27.8 State that the entropy of a system expresses its degree of disorder and describe the second law of thermodynamics in terms of entropy change.
12A.27.9 State the Kelvin–Planck formulation of the second law of thermodynamics and show an understanding of how it leads to the imposition of limits to the efficiency of any heat engine that are related to the temperatures of the heat sources and heat sinks.
526 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.3 | Physics 3 © Education Institute 2005 Activities Unit 12AP.3
Objectives Possible teaching activities Notes School resources
1 hour Energy and temperature Use this column to note your own school’s Energy and temperature Give students a handout with about ten statements relating to temperature and molecular Prepare a handout for students. Suitable kinetic energy to remind students of their earlier work. Some statements should be true, others statements include: resources, e.g. Show an understanding, in textbooks, worksheets. terms of particle energy, of the false. Some should involve converting between temperatures in K and °C. Ask students to work • Absolute zero is 0 K = –373 °C. (false) in pairs to decide which they think are true and to correct any they think are false. concept of absolute zero and • Temperature is a measure of average the absolute scale of Discuss students’ responses and ensure each has a record of a correct set of statements. molecular kinetic energy. (true) temperature, which does not If the teaching of this unit follows immediately depend on the property of any after Unit 12AP.2, it will not be necessary to particular substance. Convert spend much time on this activity. temperatures measured in kelvin to degrees Celsius. Recognise that temperature is a measure of the average kinetic energy of molecules of a substance.
6 hours Understanding heat The first law of Ask students, in pairs or individually, to use library and Internet resources to research the ICT opportunity: Use of the Internet an thermodynamics development of ideas about heat, energy and work. Allocate topics so that each pair or PowerPoint. individual researches a different person or a different theory. Tell them to prepare a 5- to10- Recognise that the first law of In addition to, or in place of, the examples minute presentation to the rest of the class using PowerPoint and/or other visual aids. They thermodynamics is a suggested here include at least one example should also write a bibliography giving full details of the sources consulted. statement of the principle of relating to Islamic science and scientists. conservation of energy. Suitable topics include the following: Explain what is meant by a • J. P. Joule and his experiments on heat. Enquiry skills 12A.1.6, 12A.1.8, 12A.2.1– thermodynamic system and • The caloric theory of heat. 12A.2.5, 12A.3.4 describe the concepts of heat, • How did the invention and use of the steam engine influence ideas about energy and heat? work and internal energy in the • What were Kelvin’s contributions to present-day ideas about heat and temperature? case of an ideal gas. • Ancient theories about the ‘elements’: fire, earth, air and water. Use the first law of Organise the rest of the lessons in this topic so that each includes one or two presentations. thermodynamics relating Either schedule the presentations in chronological order or arrange that, where possible, changes in internal energy, presentations are linked with the material being covered in the rest of the lesson. Allow a few heat changes in the system minutes for questions after each presentation. Depending on the numbers involved, it might be and work done on the necessary to devote some lessons towards the end of the topic entirely to presentations. system. Where relevant, draw students’ attention to the factors affecting the development of scientific [continued] work (e.g. the invention of steam-powered machinery stimulated thinking about energy, work and efficiency) and the way theories change with time (e.g. the caloric theory prevailed for a long time before being overthrown).
527 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.3 | Physics 3 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
[continued] Energy conservation Calculate work done by a gas Demonstrate some of the energy transducers that students used in Grade 11. Ask students to expanding against a constant describe the energy conversions and to sketch Sankey diagrams. Ask them how they would external pressure using calculate the efficiency of each device. By means of suitable questioning, ensure that students W = p∆V. are familiar with the definition of work, the distinction between heat and temperature, and the Know that internal energy is principle of conservation of energy. determined by the state of the Explain what is meant by a thermodynamic system. Define ∆Q as the heat leaving a system, system and that it can be ∆U as the increase in internal energy and ∆W as the work done on the system. Ensure that expressed as the sum of the students know the meaning of the ∆ symbol. kinetic and potential energies Briefly discuss each quantity in turn and, by suitable questioning, make links with students’ associated with the earlier work. Establish that internal energy can be expressed as the sum of kinetic and potential molecules of a system. energies of the molecules in a system; for an ideal gas, the potential energy is zero, and students should appreciate that the molecular kinetic energy, and hence the internal energy, depends only on temperature. Establish that the first law of thermodynamics, expressed as ∆W = ∆U + ∆Q, is a statement of the principle of conservation of energy. Explain that quantities must be given appropriate signs (e.g. if 100 J of heat is supplied to a system, then ∆Q = –100 J). Provide several simple numerical calculations that allow students to practise assigning correct signs to thermodynamic quantities and combining them appropriately. Work done on or by a gas Explain that, while the first law of thermodynamics is universally applicable, the focus in the remainder of this topic will be on ideal gases. Using large clear diagrams on the board or OHP, start from ∆W = F∆x to show that the work done by a gas expanding against a constant pressure is ∆W = p∆V, where ∆V is the increase in volume of the gas. Point out that, if the gas itself is the thermodynamic system under consideration, then ∆W must be a negative quantity as work is being done by (rather than on) the system. Ask students what happens to the internal energy of a gas if it does work without receiving any input of energy: the internal energy must decrease (i.e. the temperature will fall). Use the ideal gas equation to show that in this case p∆V = nR∆T. Ask students to work in pairs or small groups to explore the thermodynamic changes involved in Enquiry skills 12A.1.1, 12A.1.3, 12A.1.4, first using a bicycle pump to inflate a bicycle inner tube then releasing the valve so that air escapes 12A.1.5, 12A.3.1–12A.3.3, 12A.4.1, 12A.4.2 rapidly from the tube. Tell them to make their work as quantitative as possible and encourage them to use their initiative in devising means to measure quantities such as gas temperature and pressure. Make sure they have access to appropriate apparatus. Remind them to identify and discuss factors likely to affect any measurements and calculations (e.g. friction in the pump, heat losses to the surroundings, and the extent to which air might behave as an ideal gas). Tell students to produce a written report of their observations and measurements explaining how the first law of thermodynamics applies to each stage of the process. To help with this, introduce and define the term adiabatic (and, for completeness, isothermal). Provide plenty of algebraic and numerical examples that allow students to practise using ∆W = p∆V and ∆W = ∆U + ∆Q.
528 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.3 | Physics 3 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
4 hours Forwards and backwards The second law of Show the class a series of film or video clips of simple processes, some running forwards and Suitable examples include: thermodynamics some backwards. Ask students to say which are forwards, which backwards and which are • a glass falling to the floor and breaking; ambiguous, and then to identify the features that enable them to say which is which. Ask State that the entropy of a • ink squirted from a pipette into a beaker of students to suggest other examples of processes that occur only in one direction (e.g. a cup of water; system expresses its degree hot tea cools down – it does not spontaneously get hotter). of disorder and describe the • a bouncing ball; Establish that energy is conserved in all processes, so energy conservation cannot be a second law of • a swinging pendulum; feature that distinguishes forwards from reverse. Given suitable questioning, students will • a book sliding along a table top and coming to thermodynamics in terms of probably be able to suggest that matter being spread out in a state of increasing disorder is a rest; entropy change. characteristic of many processes that occur spontaneously (e.g. a breaking glass), whereas • a burning match. State the Kelvin–Planck processes that require a reduction in disorder (e.g. a glass reassembling) do not happen formulation of the second law spontaneously. of thermodynamics and show Get students to produce flick books to depict a simple one-way process. To do this they need to an understanding of how it draw a sequence of sketches or cartoons on adjacent pages of a small booklet so that, when leads to the imposition of the pages are rapidly flicked, there is an impression of movement. Flicking the pages from front limits to the efficiency of any to back shows a spontaneous process, whereas flicking from back to front shows a process that heat engine that are related would not occur unaided. to the temperatures of the
heat sources and heat sinks. Entropy Introduce the term entropy as meaning (loosely) disorder, and establish that a process that involves a reduction in entropy cannot happen spontaneously. Extend the notion of disorder to include energy as well as matter. Establish that heating involves a wider distribution of energy and an increase in molecular disorder, and hence an increase in entropy, and that processes involving the production of heat tend to be spontaneous. It is useful to introduce the concept of an irreversible process as one that involves an increase in entropy; the reverse process cannot occur, as it involves a reduction in entropy. Point out that it might be possible to imagine a reversible process (i.e. one that involves no entropy change so could occur either way). The swing of a pendulum suspended from a frictionless support, in the absence of any air resistance, would be reversible, but in practice there is always some heating that makes the process irreversible. Summarise these discussions by stating the second law of thermodynamics: Any process that occurs spontaneously leads to an increase in entropy. Discuss examples of processes that appear to reduce entropy, such as a liquid solidifying into a crystal. Point out that such processes must be considered in terms of everything involved. For example, crystallisation reduces the entropy of the material itself, but heat is lost to the surroundings, whose entropy therefore increases and, overall, there is a net increase in entropy. The second law of thermodynamics is, like the first law, universal: no examples have ever been found where it is violated. Discuss with more advanced students how the nature of molecular motion is related to the second law of thermodynamics. Despite the random motion of individual molecules, it is possible to make very firm predictions about the way a process will occur as described by the second law.
529 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.3 | Physics 3 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
Use Java applets to show the behaviour of a collection of randomly moving particles. If particles ICT opportunity: Use of Java applets. are placed in one half of a container then allowed to move randomly throughout all the available Enquiry skill 12A.2.6 space, they will soon become evenly distributed. While it is impossible to predict the motion of an individual particle, it is easy to predict their overall distribution when large numbers are involved. Encourage students to discuss the extent to which they think the probabilistic, random nature of molecular motion can be reconciled with the deterministic teachings of major religions. Heat engines Begin with a brief presentation given either by students (see earlier) or yourself, outlining how Enquiry skills 12A.2.1, 12A.2.2 the invention and use of steam engines influenced the development of ideas about energy and heat. Industrial users needed to maximise the efficiency of their machines, so it became important to develop an understanding of how the work done is related to the heat supplied (and hence to the fuel consumed). Introduce and explain the term heat engine as meaning any device in which a supply of heat leads to work being done. Steam engines are a historic example. More modern examples include the turbine-generator systems used in power stations and the internal combustion engine used in motor vehicles. Refer to work from earlier grades and establish that the efficiency of a heat engine is given by W ⁄ Q, where Q is the heat supplied and W the work done. By suitable questioning, lead students through the following argument to conclude that it is impossible for a heat engine to have an efficiency of 100%. First think of examples of the opposite process (i.e. work is done that leads only to the production of heat). Examples include applying the brakes to a moving car, or a book sliding along a table and coming to rest. Establish that such processes involve an increase in entropy. The reverse process will therefore not happen spontaneously. Introduce the Kelvin–Planck statement of the second law of thermodynamics: It is impossible to design a heat engine in which heat is entirely converted into work.
Temperature and efficiency Introduce advanced students to a quantitative expression for entropy. Explain that, if a quantity of heat Q is transferred at absolute temperature T, the entropy change, denoted ∆S, is given by ∆S ≥ Q ⁄ T. In a reversible change, ∆S = Q ⁄ T. Explain that ∆S can also be expressed in terms of molecular behaviour, but that it is not helpful to do so when dealing with large-scale measurements. Remind students that, similarly, absolute temperature can be understood and expressed in terms of molecular kinetic energy, but when dealing with large-scale measurements it is neither necessary nor helpful to do so. Introduce the terms heat source and heat sink and display a Sankey diagram for a heat engine
on the board or OHP. Heat Q1 is supplied from a source at temperature T1, and heat Q2 is
extracted to a sink at a lower temperature T2, enabling work W to be done. For example, in a power station, T1 is the temperature of the hot gases that drive the turbines and T2 is the Sankey diagram for a heat engine temperature of the cooling water.
530 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.3 | Physics 3 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
Let students spend a few minutes discussing in small groups how to derive an expression for
the efficiency in terms of T1 and T2. Then, using suitable questioning depending on the progress they have made, guide them through the following argument:
work done W = Q1 – Q2
efficiency = W ⁄ Q1 = Q1 – Q2 ⁄ Q1
at the heat source ∆S1 = +Q1 ⁄ T1
at the heat sink ∆S2 = – Q2 ⁄ T2
The signs of ∆S are important; the supply of heat Q1 increases the entropy of the engine,
whereas the entropy decreases when Q2 is removed. If the whole process is reversible, then the overall entropy change is zero
∆S = ∆S1 + ∆S2 = 0 So
Q1 ⁄ T1 – Q2 ⁄ T2 = 0 so Q2 = T2Q1 ⁄ T1
Substituting in the expression for efficiency and cancelling Q1
W⁄ Q1 = Q1 – Q2 ⁄ Q1 = (1 – T2 ⁄ T1) = (T1 – T2) ⁄ T1
Ask students to show that, if ∆S is greater than zero, the efficiency is reduced and hence confirm that the expression above gives the maximum possible efficiency of a heat engine, and
that is always less than 100% except in the impractical case when T2 = 0 K. Students should calculate the maximum efficiencies of some heat engines.
531 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.3 | Physics 3 © Education Institute 2005 Assessment Unit 12AP.3
Examples of assessment tasks and questions Notes School resources
Assessment An oxygen molecule has sixteen times the mass of a hydrogen molecule. If a mixture of Set up activities that allow hydrogen and oxygen molecules is at a uniform temperature, what are the ratios of students to demonstrate what a. the kinetic energies they have learned in this unit. b. the mean square speeds of the two types of molecule? The activities can be provided
informally or formally during 5 kJ of work is done on a thermodynamic system which then loses 2 kJ of heat to the and at the end of the unit, or surroundings. What is the change in the system’s internal energy? for homework. They can be A bicycle pump has internal diameter 1.5 cm and when fully extended encloses a cylinder of air selected from the teaching 20 cm long. activities or can be new a. A student finds that she exerts a pressure twice that of the atmosphere when inflating a experiences. Choose tasks bicycle tyre. How much work does she do when she pushes the piston 20 times to inflate a and questions from the tyre? examples to incorporate in
the activities. b. If 45 J of heat are lost from the system while she is using the pump, what is the change in its internal energy? (Atmospheric pressure = 1 × 105 Pa.)
Using the terms heat, work and internal energy, explain why air expanding rapidly from a balloon undergoes a drop in temperature.
Describe what happens, on a molecular level, when an ice cube melts in a glass of water. Explain how this process illustrates the second law of thermodynamics.
What is the maximum possible efficiency of a power station that drives turbines using super- heated steam at a temperature of 120 °C and extracts heat into a sink at temperature 20 °C?
532 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.3 | Physics 3 © Education Institute 2005 GRADE 12A: Physics 4 UNIT 12AP.4 9 hours Oscillations
About this unit Previous learning Resources
This unit is the fourth of seven units on physics To meet the expectations of this unit, students should already understand The main resources needed for this unit are: for Grade 12 advanced. the concepts of displacement, speed, velocity and acceleration, represent • film or video clip of the Tacoma Narrows bridge collapse The unit is designed to guide your planning and them graphically and interpret graphs that represent them. They should • battery-operated buzzer or electric toothbrush know and be able to use the terms amplitude, phase difference, period, teaching of physics lessons. It provides a link • xenon strobe lamp frequency. They should be familiar with angular displacement and angular between the standards for science and your • vibration generator lesson plans. velocity expressed using radians and should be able to use the expressions v = rω, a = rω2 and a = v2 ⁄ r. They should know that a force applied to an • flexible track (e.g. curtain track) bent into parabolic and semicircular The teaching and learning activities should help object can cause deformation (which can often be described by Hooke’s shapes and mounted on a board you to plan the content and pace of lessons. law). They should be able to define kinetic and potential energy, and • guitar or sonometer Adapt the ideas to meet your students’ needs. describe the principle of energy conservation and apply it to simple • transparent U-shaped tube For consolidation activities, look at the scheme of examples. They should have a qualitative knowledge of frictional and • shock absorber from a car work for Grade 11A. viscous forces, including air and water resistance. • Barton’s pendulums demonstration You can also supplement the activities with • hacksaw blades appropriate tasks and exercises from your school’s textbooks and other resources. Expectations Introduce the unit to students by summarising By the end of the unit, students solve mathematical problems in simple Key vocabulary and technical terms what they will learn and how this builds on earlier harmonic motion and explain practical examples of resonance, critically and Students should understand, use and spell correctly: work. Review the unit at the end, drawing out the non-critically damped oscillations and forced oscillations. • amplitude, period, frequency, angular frequency, phase angle, phase main learning points, links to other work and real Students who progress further use calculus and graphical methods to difference world applications. deduce equations for simple harmonic motion. They derive and use • oscillation, vibration, simple harmonic motion expressions for kinetic and potential energy during the motion. • free oscillation, restoring force • damping, critical damping, under-damping, over-damping • forced oscillation, natural frequency, resonance
533 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.4 | Physics 4 © Education Institute 2005 Standards for the unit Unit 12AP.4
SUPPORTING STANDARDS CORE STANDARDS EXTENSION STANDARDS 9 hours Grade 12 standards
5 hours 10A.28.3 Know and use the terms ... 12A.28.1 Describe examples of free oscillations and understand and use the terms displacement, amplitude, phase amplitude, period, frequency, angular frequency and phase difference. Oscillations difference, period, frequency ... Express the period in terms of both frequency and angular frequency.
12A.25.1 Express angular displacement in 2 hours radians ... Energy in oscillations 12A.25.2 Understand and use the concept of angular velocity to solve problems in
various situations using the formulae 2 hours v = rω, a = rω2 and a = v2 ⁄ r. Forced 10A.26.1 Understand the concepts of 12A.28.2 Deduce, by calculus or graphical methods, and use the equations for oscillations and displacement, speed, velocity and expressing the displacement, period, velocity and acceleration in simple resonance acceleration, represent them harmonic motion. graphically and interpret graphs that
represent them. 10A.26.3 Know that a force acting on an object can cause deformation ...
11A.27.2 Define kinetic and potential energy ... 12A.28.3 Describe, using graphical illustrations, the changes in displacement, Describe the principle of energy velocity and acceleration during simple harmonic motion. Describe the conservation and apply it to simple changes between kinetic and potential energy during the motion. examples. 10A.26.5 Show a qualitative knowledge of 12A.28.4 Describe and explain practical examples of critically and non-critically frictional and viscous forces including damped oscillations. air and water resistance ... 10A.28.8 ... illustrate the phenomenon of 12A.28.5 Describe practical examples of forced oscillations and resonance and resonance with particular reference show how the amplitude of a forced oscillation changes with frequency to vibrating stretched strings and air near to the natural frequency of the system. columns. 12A.28.6 Describe circumstances in which resonance is desirable and others when it should be avoided.
534 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.4 | Physics 4 © Education Institute 2005 Activities Unit 12AP.4
Objectives Possible teaching activities Notes School resources
5 hours Oscillations Use this column to note your own school’s Oscillations Show the class several examples of oscillating objects with a wide range of sizes and frequencies. Examples should include a video or film clip of the Tacoma Narrows bridge resources, e.g. Describe examples of free textbooks, worksheets. oscillations and understand collapse, a string attached to a vibration generator, and a small battery-driven oscillator such as a buzzer or electric toothbrush. and use the terms amplitude,
period, frequency, angular Use quick-fire oral questions to remind students of the terms period, amplitude and frequency
frequency and phase from earlier grades. Introduce, or remind students of, the terms oscillation and vibration, each
meaning a regular repeating to-and-fro motion. Establish that oscillation is a type of motion difference. Express the period in terms of both found in many different situations.
frequency and angular Ask students to suggest how the frequency of an oscillation can be measured. For long-period frequency. oscillations, such as those of the Tacoma Narrows bridge, they should be able to suggest that Deduce, by calculus or the period, and hence the frequency, can readily be deduced using freeze-frame video. graphical methods, and use Demonstrate the use of a xenon stroboscope to determine the frequency of a string attached to Safety: Stroboscopes can be hazardous to the equations for expressing people with epilepsy a vibration generator. By comparing settings of the strobe and the generator, establish that the displacement, period, there are several strobe frequencies that ‘freeze’ the motion, and that the vibration frequency
velocity and acceleration in must be the highest of these. simple harmonic motion. Divide the class in half, and each half into small groups. Ask students in one half of the class to ICT opportunity: Use of digital video. Describe, using graphical use digital freeze-frame video to find the frequency of the Tacoma Narrows bridge oscillations, Enquiry skills 12A.4.1, 12A.4.2 illustrations, the changes in and ask those in the other half to use a xenon strobe to find the frequency of a buzzer, electric displacement, velocity and toothbrush or similar high-frequency vibration. The two halves should then change over so that acceleration during simple all students experience both techniques. harmonic motion...
SHM or not SHM? Set up a circus of oscillating objects. Aim for a wide variety and choose some examples where Suitable examples of oscillators include: period is independent of amplitude and there is a sinusoidal variation of displacement with time • dynamics trolley tethered between two springs; (i.e. SHM) and some that behave in other ways. • ball-bearing rolling on a parabolic track; Ask students to work in pairs to explore each station of the circus in turn. Tell them to experiment • ball-bearing rolling on a semi-circular track; and note whether the period of each oscillation depends on the amplitude. Where possible, they • vibrating guitar or sonometer string; should also obtain a record showing how displacement of the oscillator varies with time. • liquid in a U-shaped tube; Discuss students’ findings with the whole class. Establish that many different types of oscillator • bouncing ball; behave in a similar way in that the period of oscillation is independent of amplitude and a graph • simple pendulum; of displacement against time is sinusoidal. Tell students that such oscillations are called simple • rigid pendulum suspended from potentiometer harmonic motion (SHM) and will be the main subject of this unit. shaft (connect the potentiometer to a DC Also establish that, while many oscillators perform SHM, not all oscillations follow this pattern power supply in series with a fixed resistor; and the analysis developed in this unit is not applicable to them. connect a CRO across the potentiometer so Students might have reached differing conclusions concerning the oscillation of pendulums: by that the displayed voltage trace indicates the suitable questioning, establish that at small amplitudes these perform SHM, but at large angular displacement of the pendulum). amplitudes the period increases noticeably. Enquiry skills 12A.1.2–12A.1.4
535 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.4 | Physics 4 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
SHM and circular motion Set up the following demonstration to show students the relationship between circular motion and SHM. Suspend a tennis ball (or similar) from a long string to make a pendulum. Mount another tennis ball on a turntable that can spin slowly about a vertical axis. Place both behind a
translucent screen and arrange a light source to cast shadows of both balls onto the screen. Adjust the length of the string and/or the rotation speed of the turntable so that both motions have the same period, and the shadows on the screen oscillate in phase and with similar amplitude. Students should observe that SHM can be treated as a projection of circular motion. Ask each student to draw, on graph paper, a circle with a radius of a few centimetres, centred on an intersection of grid lines. Tell them to mark the circumference of the circle at regular intervals (e.g. every 30°) to represent successive positions of an object moving around the circle at constant speed and observed at regular time intervals. They should then note the x (or y) coordinate of each position and plot a graph showing how this coordinate varies with time: the graphs will be sinusoidal. Let students explore this projected motion using an appropriate Java applet. ICT opportunity: Use of Java applets. Equations of SHM On the board or OHP, show students how to derive equations for SHM using a projection of Mathematics. Trigonometry and a knowledge of circular motion. angles measured in radians are required. Draw a large diagram showing an object moving anticlockwise around a circle of radius A, starting from the x-axis at time t = 0. By suitable questioning, remind students of the meaning of angular velocity, ω, and establish that, expressed in radians, angular displacement θ =ω t. Also remind them of the relationships v = rω and a = v2 ⁄ r = rω2. Choose one point on the circumference of the circle and use trigonometry to show students that the displacement in the x direction is x = r cos (ω t ). Draw a velocity vector at the same point and show that its x component is v = r ω sin (ω t ). Draw a vector representing the centripetal acceleration at the same point and show that its x component is a = –rω2 cos (ω t ). Establish that these equations describe the displacement, velocity and acceleration (respectively) of an object oscillating with SHM along the x-axis. Students should be able to identify r with the amplitude, A, of the oscillation and rewrite the equations as x = A cos (ω t ) and so on. Explain that, when dealing with SHM (rather than circular motion), ω is usually called the angular frequency (rather than angular velocity). Ask students to derive the relationships ω = 2πf and T = 2π ⁄ ω where f is the frequency and T the period of the oscillation. Now draw another similar diagram, this time showing an object starting with an angular displacement φ when t = 0. Ask students to work individually or in pairs to derive expressions for the x components of displacement, velocity and acceleration (i.e. x = A cos (ω t + φ ) and so on). Establish that the angle φ is called the phase angle, and that the phase difference between two oscillations can be denoted by the difference in their phase angles. Remind students that such angles are conventionally expressed in radians (e.g. two oscillations in antiphase have a phase difference of π).
536 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.4 | Physics 4 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
Give students plenty of opportunities to practise drawing and interpreting graphs showing how
displacement, velocity and acceleration vary with time for SHM. Mathematical derivation of SHM equations Discuss the equations derived above and establish that, regardless of the amplitude and phase, Mathematics: A knowledge of calculus is the acceleration is always proportional to the displacement and in the opposite direction required. (i.e. a = –ω2x). Show that this expression can be rewritten as d2x ⁄ dt2 = –ω2x and point out that it is a differential equation in x. By suitable questioning and discussion, show that x = A cos (ω t ), x = A sin (ω t ) and x = A cos (ω t + φ ) are all solutions to the equation. Also show that corresponding expressions for velocity can be obtained by differentiating the expressions for displacement. Point out that the values of phase angle and amplitude are independent of the angular frequency and can, in principle, take any value, depending on the particular oscillator being described. Emphasise that this is a characteristic of SHM as noted earlier: the period is independent of amplitude. Give students plenty of algebraic and numerical examples that allow them to practise using equations of SHM. Measuring SHM Ask students, in pairs or small groups, to explore in detail one example of an oscillator Suitable examples include: performing SHM. As far as apparatus permits, each pair or small group should explore a • a dynamics trolley tethered between two springs; different oscillator. Tell students to devise and use methods for obtaining an accurate record of • a magnet on a spring oscillating in and out of its motion, showing how the displacement, velocity and acceleration vary with time. The a coil (the induced emf will indicate velocity); oscillators themselves should be fairly simple, and students should be encouraged to use a • a rigid pendulum suspended from a range of methods and instruments for recording their motion, such as sensors, dataloggers and potentiometer shaft; digital video cameras. • a simple pendulum. Review work on linear motion from earlier grades with students and make sure they recall that (The amplitude of the pendulum oscillations velocity can be deduced from the gradient of a displacement–time graph, and acceleration from must be small.) the gradient of a velocity–time graph. Depending on how the initial records have been produced and stored, gradients can be found either from hand-drawn tangents or by using suitable software. Enquiry skills 12A.1.1, 12A.1.3, 12A.1.4, 12A.1.5, 12A.3.1, 12A.3.2, 12A.3.4, 12A.4.1 Ask students to summarise their results in the form of labelled graphs. These can be photocopied and distributed to the whole class. ICT opportunity: Use of dataloggers and digital video. Force and SHM Write the SHM equation a = –ω2x on the board or OHP. Establish that this relationship implies that the oscillating object must be experiencing a restoring force F that is proportional to its displacement and in the opposite direction: F = – kx. By means of suitable questioning, remind students of Hooke’s law and the behaviour of springs. Establish that, if a mass is suspended from a spring and displaced from equilibrium by a distance x, it will experience a restoring force F = –kx and must therefore perform SHM when released.
537 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.4 | Physics 4 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
Point out that, if this restoring force is the only force acting on an oscillator, it will perform so- called free oscillations. (Later in this unit there are examples of oscillations where other forces act.)
Ask students to deduce an expression for the acceleration of a mass m suspended from a
spring of stiffness k (i.e. a = –kx ⁄ m).
Then compare the two acceleration equations and identify ω2 = k ⁄ m. Establish that the angular frequency is ω = √(k ⁄ m) and hence the period and frequency of the SHM can be deduced. Emphasise that any system in which there is a restoring force proportional to displacement will oscillate with SHM, and that the angular frequency can always be deduced from the relationship between displacement and acceleration. Provide several examples that allow students to practise relating frequency and period of SHM to physical parameters of an oscillator.
Ask students to work in pairs to measure k for a spring and hence predict the frequency of Enquiry skills 12A.1.1, 12A.1.2, 12A.4.1, 12A.4.2 oscillations performed by a known mass m attached to the spring. Then ask them to determine the frequency of the SHM performed by the mass suspended from the spring and to compare their result with their prediction. On the board or OHP, show a large diagram of a simple pendulum, length l, displaced through a Mathematics: A knowledge of the small angle small angle θ. By resolving forces into components show that, provided θ is small and sin θ ≈ θ, approximation is required. the restoring force is proportional to displacement and hence the pendulum will perform SHM with angular frequency ω = √(g ⁄ l) where g is the gravitational field strength. This activity also relates to Standard 10A.25.2 Then ask students to work in pairs to determine a value of g by timing oscillations of a Enquiry skills 12A.1.1, 12A.1.3, 12A.1.5 pendulum. They should consider how best to design their experiment and process their results in order to ensure precision and accuracy and should quantify the uncertainty in their final result. Tell them to produce a brief written report of their work.
2 hours Energy and SHM Energy in oscillations Set up a demonstration of a dynamics trolley oscillating horizontally between two springs. Ask ... Describe the changes the class to describe, qualitatively, the energy of the system. By suitable questioning, establish that, when displacement is maximum, kinetic energy is zero and potential energy is maximum, between kinetic and potential while at the mid-point of the oscillation kinetic energy is maximum and potential energy is zero. energy during the [simple harmonic] motion. Students should be able to draw on their previous experience of energy transformation and conservation, and appreciate that, provided there is minimal dissipation to the surroundings, the Describe and explain total energy of the oscillator remains constant. practical examples of critically and non-critically damped Ask students to speculate about the likely shapes of graphs showing how the kinetic (or potential) energy of the oscillator varies with time and with position. Ask a few students to draw oscillations. rough sketches on the board showing their ideas, and to explain their thinking to the rest of the
class. Some students might use equations of SHM to deduce the shapes of the graphs, while others might reason qualitatively.
538 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.4 | Physics 4 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
Show, on the board or OHP, how to manipulate the equations of SHM to derive expressions for 2 2 2 2 2 2 the kinetic energy of the oscillating trolley, i.e. Ek = ½ mv = ½ mA ω sin (ω t ) = ½ kA sin (ω t ) Then get students to work in pairs to deduce similar expressions for potential energy, starting 2 from the expression for the potential energy in a stretched spring: Ep = ½ kx .
Check that students have a correct record of the equations for Ek and Ep, then use them to establish that the total energy of the oscillator is ½ kA2. Provide plenty of numerical and algebraic examples that allow students to practise using the energy equations for SHM.
Damped oscillations Ask each pair of students to suspend a mass from a spring and observe its oscillations, first in It is important to ensure that students appreciate air and then with the mass immersed in a beaker of water. Tell them to describe their that the damping being considered here is not observations as fully as possible. Prompt them with questions such as ‘What is the period of damping due to water. oscillation in each case?’ and ‘How many cycles take place before the oscillations cease?’. Examples where damping is undesirable include: Discuss students’ observations with the whole class. Establish that drag forces between the • producing a note on a guitar string; mass and the surrounding air or water always act to reduce the speed of the moving mass and • using a pendulum to regulate a clock. dissipate energy. Examples where damping is desirable include: Introduce the term damping. Establish that damping reduces the energy and hence the • oscillation of a car as it drives along a rough amplitude of the oscillations but has little effect on the frequency. road surface; Divide students into small groups and ask them to hold a brief brainstorming session. They • earthquake-induced oscillation of a building. should first try to think of examples of everyday examples of oscillations and then, for each example, say whether damping of the oscillations is desirable or not. Ask a representative of Critical damping can be explained with reference to a swing door. If under-damped, the each group to write their examples in two lists on the board or OHP. door swings to and fro many times when Discuss some of the examples in which damping is desirable with the whole class, and ask released, but if over-damped it is difficult to open them to suggest how it is achieved in practice. and takes a long time slowly to swing shut. If the Show students the construction of a shock absorber from a car – a piston immersed in oil door is well designed, so that its oscillations are ensures that oscillations are damped and that the car’s occupants have a comfortable ride. critically damped, it will easily swing shut but Choose a suitable example to illustrate the meaning of critical damping. This is best defined by without over-shooting. comparison with under-damping and over-damping. A useful working definition of critical damping is that it occurs when the oscillator returns to its equilibrium position in a time approximately equal to the period of the undamped oscillation.
If the time to return to equilibrium is considerably longer than the period, the oscillator is over- damped, and if the oscillator overshoots the equilibrium position and oscillations persist for several cycles, it is under-damped. Point out that, in most situations where damping is desirable, it is usually critical damping that is required.
539 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.4 | Physics 4 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
2 hours Forced oscillations Forced oscillations and Remind students of the examples of oscillators they saw at the start of this unit. Point out that resonance the Tacoma Narrows bridge, the buzzer or toothbrush, and the vibrating string are all examples of forced oscillations in which energy is continuously supplied to the system to maintain the Describe practical examples oscillations. Contrast these with free oscillations in which a system is disturbed then allowed to of forced oscillations and move freely under the influence of only its own restoring force and any damping forces. resonance and show how the amplitude of a forced Resonance oscillation changes with frequency near to the natural Demonstrate Barton’s pendulums to show how the frequency of a periodic driving force affects frequency of the system. the amplitude of the driven oscillator. Introduce and define the terms natural frequency and driving frequency. Establish that, when an oscillator is driven with a frequency that is close to its Describe circumstances in own natural frequency, there is a large transfer of energy and the oscillations build up to large which resonance is desirable amplitude. Introduce the term resonance. and others when it should be avoided. Show how damping affects the response of an oscillator to a periodic driving force. (Weighting the paper cones in the Barton’s pendulum demonstration reduces the effect of air resistance on
their motion and hence reduces damping.) Point out to more advanced students the relationship between the phases of the pendulums: at resonance, there is a phase difference of a quarter of a cycle between the driver and the driven pendulum. Remind students that they have already seen examples of resonance in an earlier unit when
they studied the vibration of strings and air columns. Safety: Ensure that all parts are fixed firmly Ask students to work in pairs or small groups to explore the resonance of a vibrating hacksaw together. Wear eye protection. Do not put blade using the apparatus shown in the schematic diagram. They should plot a graph showing fingers near the vibrating blade. how the amplitude, A, of the forced vibration varies with driving frequency. Enquiry skills: 12A.1.1–12A.1.4, 12A.3.1, 12A.3.2, 12A.3.4, 12A.4.1, 12A.4.2 Discuss the example of the Tacoma Narrows bridge collapse with the whole class. Explain that the gusting wind provided a driving force that matched the bridge’s own natural frequency. (Explain to more advanced students how periodic ‘vortex shedding’ allows a steady wind to produce an oscillatory force on an object.) Divide students into small groups and ask them to suggest other examples of resonance. In Examples include: each case, they should say whether the effect is desirable or not. If resonance is desirable, they • pushing a child on a swing; should suggest how it may be brought about. If it is undesirable, they should suggest how it • a singer shattering a wine glass with a loud note; might be reduced. • tuning a string instrument so that it resonates
Discuss students’ ideas with the whole class, and be prepared to suggest some examples with a tuning-fork; yourself if they have not thought of many. • vibration of parts of a car while in motion; Establish that resonance can be promoted by ensuring that the natural frequency of oscillation • vibration of machinery in a factory; is close to that of the driving force, and by reducing damping. Conversely, resonance can be • absorption spectroscopy (e.g. infrared reduced by adjusting the frequencies so that they are very different, and by increasing the spectroscopy used to determine the structure amount of damping. of molecules); • magnetic resonance imaging.
540 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.4 | Physics 4 © Education Institute 2005 Assessment Unit 12AP.4
Examples of assessment tasks and questions Notes School resources
Assessment A mass on a spring performs SHM with amplitude 4 cm and period 1.5 s, starting with a
Set up activities that allow displacement of 4 cm when t = 0. students to demonstrate what a. Calculate the angular frequency of the motion. they have learned in this unit. b. Draw graphs showing how the displacement, velocity and acceleration of the mass vary with The activities can be provided time. informally or formally during
and at the end of the unit, or A trolley of mass 0.75 kg is tethered between two springs, and a force of 6.2 N produces a
for homework. They can be displacement of 5.0 cm. The trolley is then released and it performs SHM. selected from the teaching a. Calculate the energy transferred to the trolley as it is displaced. activities or can be new b. Calculate the trolley’s kinetic energy as it passes through the mid-point of the oscillation. experiences. Choose tasks c. Calculate the maximum speed of the trolley. and questions from the examples to incorporate in On a single set of axes, sketch graphs showing how the kinetic, potential and total energy of an
the activities. oscillator vary with time as it performs one complete cycle of oscillation.
Write a short article about damping and resonance. Use at least one everyday example to explain the difference between critically damped and non-critically damped oscillations. Include one example of a situation in which resonance is desirable, and one example of a situation in which it is not.
Molecules of hydrogen chloride (HCl) are found to absorb electromagnetic radiation with a wavelength 3.47 × 10–6 m. The radiation makes the molecules oscillate at their own natural frequency. By assuming that the chlorine remains at rest while the hydrogen oscillates as if held by a spring, calculate the stiffness, k, of the interatomic bond.
Data: speed of light c = 3.00 × 108 m s–1; mass of hydrogen atom m = 1.67 × 10–27 kg.
541 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.4 | Physics 4 © Education Institute 2005
542 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.4 | Physics 4 © Education Institute 2005 GRADE 12A: Physics 5 UNIT 12AP.5 13 hours Electrostatic charge and force
About this unit Previous learning Resources
This unit is the fifth of seven units on physics for To meet the expectations of this unit, students should already know that The main resources needed for this unit are: Grade 12 advanced. opposite charges attract but like charges repel each other. They should • overhead projector (OHP) The unit is designed to guide your planning and know that electric current is the rate of flow of charged particles, define • double flame probe charge and the coulomb, and solve problems using the relationship Q = It. teaching of physics lessons. It provides a link • ball, 10–20 cm diameter, coated with conductive paint They should understand the construction of capacitors and their use in between the standards for science and your • conductive paper (sometimes known as resistive paper) lesson plans. electrical circuits. They should be able to describe an electric field as an example of a field of force, know that electric field strength can be defined as • electrolytic capacitor cut open to reveal its construction The teaching and learning activities should help force per unit positive charge, and define potential difference and the volt. • gas discharge tube connected to vacuum pump you to plan the content and pace of lessons. They should understand and be able to use the concept of a gravitational • Van der Graaff generator, signal generator, cathode-ray oscilloscope Adapt the ideas to meet your students’ needs. field as an example of a force field and define gravitational field strength as • selection of circuit components and power supplies For consolidation activities, look at the scheme of force per unit mass, and should recall and be able to use Newton’s law of work for Grades 10A and 11A. 2 universal gravitation in the form F = G(m1m2) ⁄ r . Key vocabulary and technical terms You can also supplement the activities with appropriate tasks and exercises from your Students should understand, use and spell correctly: school’s textbooks and other resources. Expectations • electric field, Coulomb’s law Introduce the unit to students by summarising By the end of the unit, students apply Coulomb’s law to charged particles • electrical potential, potential gradient, potential difference, electron-volt what they will learn and how this builds on earlier in air, solve problems related to potential difference and potential energy and • equipotential line, equipotential surface work. Review the unit at the end, drawing out the recognise the similarities between electric and gravitational fields. They • capacitor, capacitance main learning points, links to other work and real understand capacitors and solve problems relating capacitance to voltage world applications. and current. Students who progress further understand and use the concept of electric field. They can define electrical potential, relate field strength to potential gradient and solve problems involving potential energy and potential difference. They derive and use formulae for capacitors in series and in parallel, and relationships involving energy stored in a capacitor.
543 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.5 | Physics 5 © Education Institute 2005 Standards for the unit Unit 12AP.5
SUPPORTING STANDARDS CORE STANDARDS EXTENSION STANDARDS 13 hours Grade 12 standards
3 hours 10A.30.3 Describe an electric field as an 12A.29.1 Recall and use E = V ⁄ d to calculate the field strength of a uniform field example of a field of force and know between charged parallel plates, calculate the forces on charges in uniform Uniform electric that electric field strength can be electric fields and describe the effect of a uniform electric field on the field defined as force per unit positive motion of charged particles. charge and that an electric field can 3 hours be represented by means of field lines. Field and potential 10A.30.2 Know that … opposite charges 12A.29.2 State and apply Coulomb’s law relating to the force between two or more attract but like charges repel each charged particles in air and on the field strength due to a charged particle. other. 3 hours 10A.31.2 Define potential difference and the 12A.29.3 Define electrical potential at a point in an electric field, relate field strength Coulomb’s law volt ... to potential gradient, solve problems involving potential energy and and non-uniform potential difference and know and use the term electron-volt. fields 12A.25.3 Understand and use the concept of a 12A.29.4 Recognise the similarities between electrical and gravitational fields.
gravitational field as an example of a 4 hours force field and define gravitational Capacitors field strength as force per unit mass. 12A.25.4 Recall and use Newton’s law of universal gravitation in the form 2 F = G(m1m2) ⁄ r and relationships derived from it. 11A.30.1 Demonstrate an understanding of the 12A.29.5 Demonstrate an understanding of the construction and use of capacitors in construction of capacitors and their electrical circuits, and of how the charge is stored. use in electrical circuits. 12A.29.6 Define capacitance and solve problems using C = Q ⁄ V; derive and use formulae for capacitors in series and in parallel. 10A.31.1 Know that electric current is the rate 12A.29.7 Define and use the relationship between the energy stored in a capacitor, of flow of charged particles, define its charge and the potential difference between its plates. charge and the coulomb, and solve problems using the relationship Q = It.
544 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.5 | Physics 5 © Education Institute 2005 Activities Unit 12AP.5
Objectives Possible teaching activities Notes School resources
3 hours Using electric fields Use this column to note your own school’s Uniform electric field To set the scene for this unit and to help review work from earlier grades, divide students into small ICT opportunity: Use of the Internet. resources, e.g. groups and set each the task of using the Internet and other resources to research one application Enquiry skills 12A.1.6, 12A.1.8 Recall and use E = V ⁄ d to textbooks, worksheets. of electric fields. Where possible, they should collect (for later discussion) data on the strengths of calculate the field strength of the fields used and the potential differences used to produce them. Suitable examples include: a uniform field between
charged parallel plates, • ink-jet printing; calculate the forces on • LCD displays; charges in uniform electric • photocopying; fields and describe the effect • particle accelerators (e.g. LINACs and/or cyclotrons); of a uniform electric field on • electrostatic dust precipitators; the motion of charged • electrostatic spraying (e.g. crop spraying, paint spraying). particles. If necessary, remind students that an electric field is a region where a charged object
experiences a force. Ask each group to prepare a poster summarising their findings, giving particular emphasis to the role played by electric fields and including an acknowledgment of the sources consulted. Display the posters and allow time for students to view and talk about them.
Uniform electric field By means of some quick-fire questions, ascertain how much students recall from work on electric fields in earlier grades. By suitable questioning, remind them how electric field strength is defined, and how this can be expressed in SI units of N C–1. Demonstrate these two examples of a uniform electric field. • Support two metal plates vertically on insulating stands so that they are parallel and a few Safety: When using an EHT supply, ensure that centimetres apart. Connect them to the terminals of an EHT supply and set the voltage to a the safety resistor is connected and that no one few kilovolts. Fix a small piece of thin flexible metal foil to the end of an insulating rod. Charge can come into electrical contact with the the foil by touching it on one of the plates. Using the rod, move the foil around within the terminals. space between the plates; note the size and direction of its deflection.
• Pour some glycerol into a transparent, flat-bottomed container, float grass seeds or rice grains on its surface and place it on an OHP. Using flexible leads, connect two metal strips to either side of the spark gap of a piezo-electric gas lighter. Place the strips in the glycerol so that they are parallel, and use the lighter to produce an electric field within the glycerol. Observe the electric field lines revealed by the grains. Use suitable questioning to remind students that the field direction is defined to be that of the force on a positive charge. Also remind them how a field can be represented by electric field lines, and how field strength is related to the spacing of the lines: the closer the lines, the stronger the field. Ask students to suggest how the strength of an electric field between two parallel metal plates might be controlled. Drawing on their own researches in the previous activity, and by discussing the two examples demonstrated, they will probably be able to suggest that increasing the voltage and/or moving the plates closer together would produce a stronger field.
545 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.5 | Physics 5 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
On the board or OHP, show students how potential difference and distance are related to field This discussion also relates to Standard strength in the case of a uniform field produced by connecting a potential difference V between 10A.25.1 two parallel plates separated by a distance d. Remind them of the term potential difference (encourage them to use it in place of the looser ‘voltage’) and of the relationship between change, pd and energy. Show that, if a charge q moves through a pd V, then the work done is W = qV. Then remind them that the work done by a force F moving something through a distance d is W = Fd and show that V ⁄ d = F ⁄ q = E. Students should be able to show that 1 N C–1 = 1 V m–1, and hence that either unit can be used to express electric field strength. Provide numerical and algebraic examples that allow students to practise using relationships involving force, charge and electric field expressed in N C–1 and V m–1.
Potential gradient Set up and demonstrate a double flame probe as shown in the diagram on the right. Explain the probe’s operation to students and establish the following points. • The small flames at the needle tips ionise the air, allowing charge to flow until there is no potential difference between the needle tips and their surroundings. • The deflection of the gold-leaf electroscope indicates the potential difference, ∆V, between its plate and case. Connect the plate and case to an EHT supply and calibrate the electroscope by noting the deflection of the leaf for various pds. (Shine a lamp through the electroscope so that a shadow of the leaf is cast on the translucent casing. Use an erasable felt-tip pen to mark positions of the shadow.) • The probe allows the field strength to be calculated: E = ∆V ⁄ ∆d, where ∆d is the separation of the needle-tips. • In a uniform field such as that between two parallel plates connected to a potential difference,
the potential gradient ∆V ⁄ ∆d is the same everywhere in the field. Source: Salters Horners Advanced Physics A2 • The probe also reveals the direction of the field: when the needle tips are aligned along a Teacher and Technician Resource Pack, field line, the deflection of the gold leaf is maximum, and, if the probes are at right-angles to Heinemann Educational. © 2001 University of the field, the deflection is zero. York Science Education Group. Use two parallel plates and an EHT supply to produce a uniform field. Show that the field as indicated by the flame probe is indeed uniform and acts at right-angles to the plates. Ask students to produce a brief written account of this demonstration.
546 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.5 | Physics 5 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
3 hours Acceleration and ionisation Field and potential Carry out some demonstrations that show gas ‘discharge’ (i.e. ionisation by an electric field) Suitable demonstrations include the following. Define electrical potential at a and discuss them with the class. Establish the following points. • An air-filled tube that can be connected to an point in an electric field, relate • Within any gas, there are always a few charged particles (i.e. electrons and positive ions). EHT supply and a vacuum pump. Begin with field strength to potential • In an electric field, the charged particles accelerate. the tube containing air at normal atmospheric gradient, solve problems • The accelerated particles collide with other particles in the gas. pressure: the EHT fails to produce a involving potential energy and • If the collisions are sufficiently energetic, energy is transferred to electrons within atoms and discharge. With the EHT still connected, potential difference and know molecules, which are then said to be excited. evacuate air from the tube until a discharge is produced (the gas will glow pink). and use the term electron- • If the collisions are still more energetic, electrons can be dislodged from neutral atoms and volt. molecules, causing ionisation. • A Van der Graaff generator producing a spark between the main dome and a nearby small • Excited electrons lose their excess energy by emitting visible light. sphere. • Electrons liberated during ionisation undergo acceleration in the electric field, giving rise to • A fluorescent lighting tube connected in a further excitation and ionisation (i.e. a discharge or spark is produced). domestic light fitting. Discuss why a discharge or spark occurs more readily in low-pressure gas. Establish that
reducing the pressure reduces the gas density, and hence increases the average distance between particles. In a high-pressure gas, accelerated particles can only move a short distance before being involved in a collision and transferring some of their energy. If the pressure is reduced, the accelerated particles can move further and hence acquire more energy between collisions. On the board or OHP, remind students how the energy acquired by a charged particle accelerating in an electric field can be related to the field strength E and to the distance travelled d. Establish that when a particle of charge q moves through a distance d along the direction of the field, it moves through a potential difference V = Ed so that it acquires kinetic
energy Ek = qV = qEd. Explain that, when dealing with the acceleration of individual ions and electrons, it is convenient to express charge in units of the electron charge, e, and energy in electron-volts (eV). Students should be able to show that 1 eV = 1.60 × 10–19 J. Explain that the eV is a non-SI unit of energy, but that it is very widely used to express small energies and is not restricted to energies of electrically accelerated charged particles. Provide students with plenty of examples that allow them to practise using the electron-volt as an energy unit.
547 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.5 | Physics 5 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
Potential at a point In a whole-class discussion and demonstration, introduce the concept of potential at a point, first within an electric circuit and then within an electric field. Connect a long potentiometer wire to a battery. Use a voltmeter to measure the pd between several pairs of points. Point out that the term potential difference implies a difference between two values of a quantity called potential. Explain that, in a DC electric circuit, it is conventional to define the zero of potential as being at the negative battery terminal, so that all other points in the circuit are at a positive potential. Go on to explain that this choice is arbitrary, and that any point in the circuit could in principle be defined as the zero without altering the potential differences measured anywhere in the circuit. Remind students of the relationship between pd and energy, and establish that a pd of 1 V corresponds to an energy difference of 1 J for 1 C (1 coulomb) of charge. Establish that electrical potential at a point is thus the potential energy of 1 C of charge at that point. Remind students that, like the zero level of electrical potential, the choice of zero level of gravitational potential energy is also arbitrary: in both cases, we only ever measure differences rather than absolute values. Provide plenty of examples that allow students to practise using the relationships between pd and energy and describing them using appropriate terminology. Place a sheet of conductive paper on a pin-board. Attach a straight metal strip close to each Suitable field configurations include the end of the paper so that there is good electrical contact between paper and metal. Connect the following: metal strips to a low-voltage battery to produce an electric field within the paper. Connect one • two non-parallel straight metal strips; terminal of a voltmeter to the negative strip, and show students how to use a flying lead • two ‘point charges’ (i.e. metal pins) inserted connected to the other terminal to identify points within the paper that are at a potential of, say, into the board; 1 V relative to the negative strip. Introduce the terms equipotential line and equipotential surface • combinations of straight and curved metal and establish that these must always be at right-angles to electric field lines. strips; Ask students to work in pairs using conductive paper to explore the equipotential lines in various • combinations of one metal strip and one point. two-dimensional electric field configurations. Explain how to record the equipotentials by placing Enquiry skills 12A.3.1, 12A.3.2, 12A.4.1 a sheet of carbon paper face down under the conductive paper and on top of a sheet of plain white paper, and pressing down onto the paper with the flying lead. Then tell them to remove the record of the equipotentials and draw in the field lines by inspection. Display and discuss students’ records of field and equipotential lines and establish that field lines and equipotential each provide a graphic means of representing electric field strength. Establish that in a uniform field the equipotentials are equally spaced, whereas in a non-uniform field they are closest together in regions where the field is strongest. Point out that the field lines converge towards ‘point charges’ and that in such regions the equipotentials are close together.
548 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.5 | Physics 5 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
3 hours Field of a point charge Coulomb’s law and non- Ask students each to make a rough sketch showing the electric field lines that they would uniform fields expect to be associated with a point, or a uniform sphere, of charge. (If necessary, remind them that the field lines indicate the direction of the force acting on a positive charge placed in the State and apply Coulomb’s field.) Discuss students’ ideas and establish that the field lines must radiate equally in all law relating to the force directions from the charge. between two or more charged particles in air and Display a clear diagram on the board or OHP showing some of the field lines from a point on the field strength due to a charge passing through a square window of side x placed a distance r from the centre of the
charged particle. charge (x should be smaller than r ). Add a second square, side 2x, at a distance 2r. Establish that the number of lines per unit area is an indicator of field strength. Ask students to predict the Recognise the similarities relative strength of the field at the two distances shown, then ask them to predict the strength at between electrical and distance 3r. gravitational fields. Establish that the field is predicted to vary inversely with the square of the distance. Remind students that they have met a very similar pattern when studying gravitational fields.
Demonstrate the use of a double flame probe to explore the strength and direction of the field of a uniform sphere of charge. Coat a large ball (10–20 cm diameter) with conducting paint and hang it from an insulating suspension at least 1 m from the bench top and other surfaces. Connect the ball to the positive terminal of an EHT supply (use metal foil and a crocodile clip to ensure a good electrical contact). Use the flame probe to show that the field direction is radial and the field strength diminishes with distance. (Measurements of leaf deflection will probably not be precise enough to show conclusively that the field obeys an inverse-square law.)
549 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.5 | Physics 5 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
Coulomb’s law Establish by suitable questioning and discussion that, if the field from a point charge follows an inverse-square law, then so should the force between two charges. Tell students that this is 2 indeed the case and introduce Coulomb’s law F = Q1Q2 ⁄ 4πε0r . Show how Coulomb’s law leads to an expression for the strength of the electric field of a point charge. Tell students that the same expression also describes the field of a uniform spherical charge distribution, where r is the distance from its centre.
Ask students to deduce the SI units of the constant ε0 (the permittivity of free space). Point out that its value could, in principle, be determined by experiment. Ask students, in pairs or small groups, to use the apparatus shown on the right to explore
Coulomb’s law and obtain an order-of-magnitude estimate of the value of ε0. Tell them to try to obtain data relating force, charge and distance, and plot suitable graphs to see how closely their data follow an inverse-square law. Emphasise that they should pay particular attention to the accuracy and precision of their measurements and suggest ways in which the method could be improved. Provide plenty of algebraic and numerical examples for students to practise using Coulomb’s
law and the related expression for electric field strength. Source: Salters Horners Advanced Physics A2 Teacher and Technician Resource Pack, Heinemann Educational, p.139. © 2001 University of York Science Education Group. Enquiry skills 12A.1.1–12A.1.3, 12A.1.5, 21A.3.1–12A.3.3 This activity also relates to Standard 10A.25.2. In practice, it is difficult to obtain reliable data from this experiment since charge leaks away rapidly. Humid conditions increase the difficulty. Use a hair-drier to keep the apparatus as dry as possible.
550 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.5 | Physics 5 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
Electric and gravitational fields Draw students’ attention to the fact that both electrical and gravitational fields and forces due to point charges or masses are described by inverse-square laws. Divide students into small groups and ask them to brainstorm for a few minutes and list all the similarities and differences that they can think of between the two types of field and force. Discuss students’ suggestions with the whole class and summarise them on the board or OHP. If necessary, prompt students by suitable questioning if there are important comparisons that they have not thought of, including the following: • for point objects, both obey an inverse-square law; • both can be represented by field lines; • gravitational force is always attractive whereas electrostatic forces can be attractive or repulsive; • the forces due to several objects combine vectorially ...; • ... so electrostatic forces can cancel one another. Tell students to make a chart or table comparing the two types of field.
Understanding electricity Ask students to describe any models (mental pictures) that they have used to aid their understanding of electricity, such as the carrier and driver models (outlined in Unit 10AP.7). Tell them that such models have played – and continue to play – an important role in our understanding of electricity. Ask students to work in pairs to use books and the Internet to trace the historical development ICT opportunities: Use of the Internet; use of of ideas about electricity. Assign each pair to a different topic, or scientist, and ask them to word processing. produce a short summary (1–2 pages) of their findings, preferably in word-processed electronic Enquiry skills 12A.1.6, 12A.1.8, 12A.2.1 form. Suitable topics include the following: • early two-fluid models (Du Fay); • single-fluid model (Franklin); • the modern atomic model of matter; • the development of ideas about field to describe ‘action at a distance’; • particle exchange models to describe ‘action at a distance’. Collect all the students’ contributions together and copy and distribute them to the whole class.
551 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.5 | Physics 5 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
4 hours Capacitors in circuits Capacitors Remind students of their work in earlier grades by setting up several circuits demonstrating the Safety: When using an EHT supply, ensure that behaviour of capacitors. Either arrange these in a circus so that pairs of students visit each in the safety resistor is connected and that no one Demonstrate an turn, or perform a sequence of demonstrations to the whole class. Students should make brief can come into electrical contact with the understanding of the notes on each. Suitable examples include the following. terminals. construction and use of capacitors in electrical • Charge a large capacitor by connecting it to a battery, then discharge it through a lamp. circuits, and of how the Repeat, replacing the lamp by (in turn) a small motor, an LED and a microammeter. charge is stored. • Connect a capacitor in series with a resistor and a signal generator set to give a square-wave input. Either connect a cathode-ray oscilloscope (CRO) in parallel first with the capacitor then Define capacitance and with the resistor or use a dual-beam CRO to show both outputs simultaneously. Select the solve problems using resistance R and capacitance C capacitor so that RC is about 0.1 s. Start with the signal C = Q ⁄ V; derive and use frequency set to about 50 Hz then observe the effect of gradually increasing and reducing the formulae for capacitors in frequency: at low frequencies there is time for complete charge and discharge, while at high series and in parallel. frequencies the pd across the resistor is indistinguishable from the square-wave input. Define and use the • Connect a single diode in series with a resistor and a low-voltage AC power supply. Connect relationship between the a CRO across the diode to show half-wave rectification. Show the smoothing effect of energy stored in a capacitor, connecting a capacitor into the circuit. Repeat, replacing the single diode with a full-wave its charge and the potential rectifier made from four diodes. difference between its plates. • Set up a delayed-action switching circuit. Show how changing the resistance and/or the capacitance affects the time delay. • Establish that a capacitor stores electric charge and, when connected into a circuit, can act as a short-lived battery whose terminal pd falls to zero during discharge. • Set up two metal plates (e.g. 20 cm × 20 cm) so that their planes are vertical and parallel to each other a few centimetres apart. Connect the plates to the terminals of an EHT supply. Previously, students have focused on the electric field between the plates, but now they should describe what they think is happening within the wires and plates when the EHT is switched on and the plates become charged. Explain that the pair of plates is acting as a capacitor: charge can flow to and from the plates but cannot cross the gap. Show students the construction of an electrolytic capacitor and establish that the foils are behaving like the metal plates: there is no conducting path between them.
Charging and discharging Provide each pair of students with a large capacitor and resistor, two analogue ammeters and a Enquiry skills 12A.4.1, 12A.4.2
battery that can be tapped to provide 1.5, 3, 4.5 and 6 V. Provide a briefing sheet that guides students through the following sequence of experiments illustrating capacitor charge and discharge. 1 Connect one meter to each side of the capacitor in series with the resistor and to a pd of 1.5 V. Observe the meter readings as the capacitor is charged. 2 Replace the battery by a conducting wire to discharge the capacitor. 3 Repeat, using 3 V instead of 1.5 V. 4 Charge the capacitor first by connecting to 1.5 V, then, without discharging, to 3 V, then 4.5 V, then 6 V.
552 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.5 | Physics 5 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
As an extension, ask students to explore the effect of using different capacitors and resistors. Discuss students’ observations and establish the following points. • During charge and discharge, charge flows throughout the circuit. There is no net transfer of charge from battery to capacitor: rather, charge is redistributed so that one terminal of the capacitor becomes negative (gains electrons) and the other becomes positive (loses electrons). • The amount of charge flowing can be estimated by observing the ammeter readings. Increasing the battery pd in equal steps gives rise to the same amount of charge flowing each time. • When a capacitor is charged from zero, the total amount of charge flowing is directly proportional to the battery pd. Introduce and define capacitance, C, as the proportionality constant relating charge Q to pd V: –1 Q = CV. Introduce the SI unit of capacitance, the farad, F: 1 F = 1 CV . Explain that most practical capacitors have capacitances much less than 1 F, so values are usually expressed in µF or pF.
On the board or OHP, explain to students how the current, pd and charge vary while a capacitor
is discharging though a resistor. Use graphs to show how each of these quantities varies with time. Start with a graph of pd against time: students will have already seen this displayed as a trace on a CRO. Establish that, as the stored charge, Q, is proportional to V, a graph of Q against t will have the same shape as the V–t graph. Ask students to sketch their suggested shape for a graph of discharge current, I, against time. Then establish that, as I = V ⁄ R, where R is the resistance in the circuit, this graph, too, will have the same shape. Extend this discussion to include the shapes of graphs associated with a charging capacitor. Ask students to suggest how changing the capacitance and/or the resistance would affect the discharge graphs. Establish that increasing either or both will increase the time taken for the pd and other quantities to fall by a given fraction, and that a suitable choice of R and C underlies the successful design of capacitor timing circuits, Provide plenty of algebraic and numerical examples that allow students to practise using the relationship between charge, pd, current and capacitance. Measuring capacitance Show students how to use a vibrating reed switch, driven by a signal generator, to produce Enquiry skills 12A.1.1–12A.1.3, 12A.1.5, repeated charging and discharging of a capacitor made from two large metal plates. Discuss 12A.3.1–12A.3.3, 12A.4.1, 12A.4.2 how the discharge current I is related to the charge Q stored and discharged during each cycle, and the switch frequency f: I = Qf = CVf. Discuss how measurements of this current can be used in conjunction with a knowledge of the supply pd, V, to determine the value of C. Ask students to consider the strengths and weaknesses of this method. A strength is that current can be measured at several different frequencies and C determined from the gradient of a graph of I against f, thus averaging over several sets of measurements. A weakness is that, at high frequencies, there might not be time for the capacitor to discharge fully. If resources permit, let students work in small groups to carry out this experiment themselves.
553 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.5 | Physics 5 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
Combining capacitors If there is enough apparatus, ask students to work in pairs or small groups to study the charging and discharging of various combinations of capacitors using a CRO and a signal generator. Alternatively demonstrate this to the whole class. Connect a single capacitor in series with a resistor and a signal generator giving a square-wave output, and connect a CRO across the capacitor. Choose values of R and C and/or adjust the signal frequency so that there is almost complete discharge during each cycle. Without making any further alterations to the resistance or the frequency or the CRO settings, connect a second and then a third identical capacitor in parallel with the first: the discharge takes longer, indicating that the capacitance has increased. Return to the single capacitor, then connect a second and then a third identical capacitor in series with it: now the capacitance has decreased so the discharge takes a shorter time. On the board or OHP, show students how to derive expressions for combining capacitors in series and in parallel. Explain that when they are joined in parallel the capacitors all have the same pd across them, and the charge stored by the combination is equal to the sum of the
individual charges: Q = Q1 + Q2 + Q3 + ..., hence C = Q ⁄ V = C1 + C2 + C3 + ... Then explain that, when capacitors are joined in series, charge must be distributed in such a way that each stores the same charge Q, which is the same as the charge stored by the
combination. Therefore Q ⁄ C = V = V + V + V = Q ⁄ C1 + Q ⁄ C2 + Q ⁄ C3 + ..., and hence
1 ⁄ C = 1 ⁄ C1 + 1 ⁄ C2 + 1 ⁄ C3 + ...
Point out that, while these expressions resemble those for combining resistors, here the simple additive relationship applies to capacitors in parallel, whereas a similar relationship applies to resistors in series. Provide plenty of algebraic and numerical examples that allow students to practise using the relationships for capacitors in series and parallel. Energy in capacitors Mathematics: A knowledge of integral calculus is helpful but not required. Perform some short demonstrations to show that capacitors store energy. Suitable examples include: Enquiry skills 12A.1.2, 12A.4.1, 12A.4.2 • a camera flash-gun; • discharge a large capacitor through a motor set to lift a small weight; • discharge a large capacitor through a coil of wire wrapped around a temperature sensor. On the board or OHP, show students how to derive an expression for the energy stored in a charged capacitor. Depending on the mathematical fluency of the students, use a graphical method and/or integral calculus to show that energy = ½ QV. Ask students to deduce expressions for stored energy in terms of (a) C and V, and (b) C and Q. Point out the analogy between charging a capacitor and stretching a spring.
554 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.5 | Physics 5 © Education Institute 2005 Objectives Possible teaching activities Notes School resources Ask students to work in pairs to explore the energy stored in a capacitor. Provide each pair with apparatus and a briefing sheet to guide them though the following sequence of experiments. 1 Charge a large capacitor by connecting it to a 1.5 V cell, then discharge it through a single torch bulb. Repeat a few times and note the visual appearance of the bulb during discharge. 2 Charge the same capacitor using a 3 V battery. Discharge it through two bulbs connected in series (so as to ensure the same initial pd across each). Note the brightness of the flash (it is brighter than in step 1). 3 Connect a second pair of bulbs in parallel with the first and repeat step 2. Note the brightness of the flash from each bulb (the flash from each bulb is now similar to that produced in step 1). 4 Predict the effect of charging the same capacitor with a 6 V battery. Decide how many bulbs, and in what arrangement, would allow each one to give the same flash as the single bulb in step 1. (Nine bulbs are required, connected in a 3 × 3 array.)
Discuss the outcome of this activity and establish that the results are as expected (i.e. energy is directly proportional to V 2). Provide plenty of algebraic and numerical examples that allow students to practise using relationships involving energy storage in a capacitor.
555 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.5 | Physics 5 © Education Institute 2005 Assessment Unit 12AP.5
Examples of assessment tasks and questions Notes School resources
Assessment A potential difference of 2.5 kV is applied to a pair of parallel metal plates separated by 8 cm.
Set up activities that allow What is the force experienced by a charge of 6.0 mC within the space between the plates? students to demonstrate what Use Coulomb’s law to derive an expression for the magnitude of the electric field strength E at a they have learned in this unit. distance r from a point charge Q. The activities can be provided informally or formally during In a hydrogen atom, the average distance between the proton and the electron is about
and at the end of the unit, or 0.037 nm. Calculate the magnitude of the force between them. –19 for homework. They can be (Electron charge e = 1.60 x10 C.) selected from the teaching List at least two ways in which electrical and gravitational fields are similar, and at least two activities or can be new ways in which they differ. experiences. Choose tasks and questions from the At particle physics laboratories such as CERN, the kinetic energies of accelerated particles are examples to incorporate in often expressed in MeV. the activities. a. What is 1 MeV expressed in joules? b. If a proton has kinetic energy 1.5 MeV, what is its speed?
–19 –27 (Electron charge e = 1.60 x 10 C. Proton mass mp = 1.67 x 10 kg.)
Draw a diagram showing the electric field lines and the lines of equipotential around two positive point charges placed a few centimetres apart.
Draw a labelled set of sketch graphs to show how the pd across a capacitor, the charge stored and the current in the circuit change with time as the capacitor discharges through a resistor. On the same axes, draw another set of graphs showing how the pd, charge and current would change with time if the original resistor were replaced by one with greater resistance.
A 100 µF capacitor is connected to a 3 V battery then discharged through a 500 Ω resistor. Calculate: a. the initial charge stored; b. the initial discharge current; c. the discharge current when the capacitor has lost half its initial charge.
Three capacitors, of capacitance 1, 2 and 4 pF, are connected (a) in series, (b) in parallel. Calculate the resulting capacitance in each case.
A 10 000 µF capacitor is connected to a 12 V battery then discharged through a lamp. How much energy is emitted?
556 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.5 | Physics 5 © Education Institute 2005 GRADE 12A: Physics 6 UNIT 12AP.6 14 hours Quantum and nuclear physics
About this unit Previous learning Resources
This unit is the sixth of seven units on physics for To meet the expectations of this unit, students should already know that light The main resources needed for this unit are: Grade 12 advanced. can be dispersed to form a spectrum and should be able to describe • gold-leaf electroscope with very clean zinc plate The unit is designed to guide your planning and electromagnetic radiation in terms of waves. They should be able to • ultraviolet lamp and infrared heater describe a simple model of the atom in terms of protons, neutrons and teaching of physics lessons. It provides a link • photocell and circuit components to measure the stopping potential electrons, and show an understanding of the properties of the electron. They between the standards for science and your • discharge lamps (e.g. neon, helium, sodium, mercury) lesson plans. should be able to describe the processes of nuclear fission, fusion and decay, and know that such processes release energy. • hand-held spectroscopes The teaching and learning activities should help • grating spectrometer you to plan the content and pace of lessons. • iodine or mercury vapour lamp for demonstrating absorption spectra Adapt the ideas to meet your students’ needs. Expectations • electron diffraction tube For consolidation activities, look at the scheme of By the end of the unit, students distinguish between emission and • deflection tube and Helmholtz coils work for Grade 11A. 2 absorption spectra. They recall and use the relationships E = hf and E = mc • apparatus for Millikan’s oil-drop experiment You can also supplement the activities with and explain the quantisation of charge and electromagnetic radiation and appropriate tasks and exercises from your • chain or thick cord approximately 1 m long know some applications and consequences of this. They know the source of school’s textbooks and other resources. • vibration generator nuclear energy. Introduce the unit to students by summarising Students who progress further explain electron orbitals in terms of what they will learn and how this builds on earlier quantisation of angular momentum and know how quantum theory leads to Key vocabulary and technical terms work. Review the unit at the end, drawing out the the idea of electron ‘probability clouds’. main learning points, links to other work and real Students should understand, use and spell correctly: world applications. • photoelectric effect, photoelectron, quantum, quantisation, photon, work function, threshold frequency, Planck constant • line spectrum, continuum, emission spectrum, absorption spectrum • energy level, ground state • de Broglie wavelength, wave–particle duality • angular momentum, orbital • quantum mechanics, Schrödinger equation • binding energy, mass defect
557 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.6 | Physics 6 © Education Institute 2005 Standards for the unit Unit 12AP.6
SUPPORTING STANDARDS CORE STANDARDS EXTENSION STANDARDS 14 hours Grade 12 standards
5 hours 11A.29.3 Use a diffraction grating to show 12A.30.1 Distinguish between emission and absorption spectra; know how these can 12A.30.1 Distinguish between emission and diffraction and the production of (part) provide information on the elements present ... absorption spectra; know how these Radiation and visible spectra … can provide information on the spectra elements present in stellar objects and
how far away the objects are. 5 hours 11A.29.6 Explain electromagnetic radiation in 12A.30.2 Know about the particulate nature of electromagnetic radiation; recall and The electron terms of oscillating electric and use the formula E = hf. magnetic fields and know that all 2 hours electromagnetic waves travel with the same velocity in free space. Electrons in Describe the main characteristics atoms and applications of the different parts of the electromagnetic spectrum ... 2 hours 11A.32.2 Describe a simple model for the 12A.30.3 Explain atomic spectra and permitted electron orbitals in terms of the Light, energy and nuclear atom in terms of protons, quantisation of angular momentum. matter neutrons and electrons ... 12A.25.6 Derive, and use expressions relating the kinetic, potential and total energy of an orbiting satellite. 11A.32.9 Show an understanding of the 12A.30.4 Show an understanding of the quantisation of electronic charge as properties of the electron and the demonstrated, for example, by Millikan’s experiment. operation of the cathode-ray tube 12A.30.5 Show an understanding of wave–particle duality in the properties of the and the television tube. electron. 11A.32.7 Distinguish between nuclear fission 12A.30.6 Show an understanding of the interconversion of matter and energy and 12A.31.5 Explain the process of element and nuclear fusion ... use the equation E = mc2 and recognise that this explains the phenomenon formation in stars and know how this 11A.32.8 Understand that ... nuclear fission of nuclear energy. leads to the generation of energy. can be used ... as a source of energy ... 12A.25.2 Understand and use the concept of 12A.30.7 Know how the Schrödinger model for the hydrogen atom leads to the angular velocity to solve problems in concept of discrete energy states for electrons and to the idea of the various situations using the formulae probability of finding an electron at any point (related to the square of the v = rω, a = rω2 and a = v2/r. amplitude of the wave function) and hence to the concept of ‘electron 10A.28.8 ... know the meaning of the terms clouds’. node and antinode, and illustrate the phenomenon of resonance with particular reference to vibrating stretched strings and air columns.
558 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.6 | Physics 6 © Education Institute 2005 Activities Unit 12AP.6
Objectives Possible teaching activities Notes School resources
5 hours The photoelectric effect Use this column to note your own school’s Radiation and spectra Perform the following demonstration to the whole class. Use a gold-leaf electroscope with a very clean zinc plate. First give the plate a negative charge (e.g. by connecting it temporarily to resources, e.g. Distinguish between emission textbooks, worksheets. and absorption spectra; know the negative terminal of a DC power supply). Show that shining ultraviolet (UV) radiation onto the plate discharges it, while intense visible or infrared radiation (IR) from a radiant heater has how these can provide no effect. Repeat using a positively charged plate: no radiation has any effect. information on the elements present ... Divide the class into small groups and ask them to brainstorm and suggest explanations for what they have observed. Note all their suggestions on the board or OHP. Know about the particulate nature of electromagnetic Discuss students’ suggestions with the whole class and use suitable questioning to establish radiation; recall and use the the following points. formula E = hf. • Radiation can cause the electroscope to lose negative charge. • The electroscope discharges because electrons escape from it. • The UV radiation causes electrons to be emitted from the zinc. • Even very intense visible or IR radiation is unable to cause the emission of electrons, whereas weak UV can do so. • The radiation must be transferring energy to the electrons in the plate in order to cause their emission. • The way in which the energy is delivered (i.e. the type of radiation) is important, whereas the total amount of energy (or power, or intensity) is not. Introduce and define the terms photoelectric effect and photoelectron. Tell students that the effect was the subject of great interest in the late nineteenth and early twentieth centuries. Divide the class into small groups and ask them to use what they know about the wave nature of electromagnetic radiation to explain the photoelectric effect. Discuss their ideas with the whole class and establish that a wave model cannot explain the observations. Point out that a wave model predicts that intense radiation of any wavelength would transfer energy to the metal so that eventually many electrons would escape when the metal became hot enough (i.e. there would be thermionic emission). Contrast this prediction with observation: even weak UV radiation causes the instant emission of electrons from a cold metal, whereas intense visible or IR has no effect. Explain to students how the photoelectric effect can be understood. Introduce and define the terms quantum, quantisation and photon. Point out that the explanation requires that photons of UV radiation are more energetic than those of IR or visible radiation. Introduce the formulae E = hf = hc ⁄ λ and point out that they describe the relationship between the wave model of light (which deals with frequency and wavelength) and the photon model (which deals with energy of individual quanta). Introduce the Planck constant h and establish its SI units.
559 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.6 | Physics 6 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
Energy of photoelectrons
Explain to students how the initial kinetic energy of photoelectrons, Ek, can be measured by Enquiry skills 12A.1.1, 12A.1.3, 12A.3.1– applying an adverse potential difference across a photocell: Ek = eV, where V is the pd that just 12A.3.4, 12A.4.1 prevents electrons crossing the cell. If sufficient apparatus is available, ask students to work in pairs to take measurements using a photocell illuminated by radiation of various frequencies (produced by shining light through various filters) Alternatively, demonstrate this to the whole class and generate a set of measurements for all students to use. Tell students to plot a graph of V against f. Discuss the graphs with students. Introduce and explain the terms threshold frequency and work function. Establish how values of these for a given metal, and for the Planck constant, can be determined from the graphs. Provide plenty of numerical and algebraic examples that allow students to practise using formulae relating to the photoelectric effect. The nature of light Divide the class into pairs and give each pair the task of using library or Internet resources to ICT opportunity: Use of the Internet. research one topic relating to the historical development of our understanding of the nature of Enquiry skills 12A.1.6, 12A.1.8, 12A.2.1, electromagnetic radiation. Suitable topics include the following. 12A.2.4, 12A.2.5, 12A.3.4 • Isaac Newton’s theory of corpuscles.
• Islamic scientists’ theories of light. • Thomas Young’s experiments with waves. • The discovery of infrared radiation. • Hertz and radio waves. • Maxwell’s theory of electromagnetic waves. • Planck, Einstein and the photoelectric effect. Each pair should produce an A3 poster summarising what they find. Display these around the lab in chronological order and then discuss them with the whole class. Establish that, in the eighteenth and nineteenth centuries, scientists were addressing the question of whether light behaved either as a wave or as a particle, but study of the photoelectric effect revealed that neither model was exclusively applicable. Nowadays, we use both models and choose whichever is appropriate for a particular situation.
560 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.6 | Physics 6 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
Line spectra Set up a circus of activities relating to line spectra. Tell students to work in pairs to visit each in Safety: Students must not look directly at the turn and record their observations and measurements. Suitable activities include the following. Sun either with their naked eyes or through an instrument. • Look through a fine diffraction grating at the spectra produced by various discharge lamps (e.g. neon, helium, sodium, mercury). Enquiry skills 12A.4.1. 12A.4.2
• Use a grating spectrometer to measure the first-order diffraction angles of visible light from a hydrogen and/or a mercury lamp. (More advanced students could, if time permits, use their measurements to determine the wavelengths present.) • Use a hand-held spectroscope to observe the spectrum of sunlight scattered from a pale matt surface (e.g. a whitewashed wall, clouds, white paper).
• Use a hand-held spectroscope to study the absorption spectrum of iodine or mercury in a
vapour lamp. Discuss students’ observations, introduce the terms line spectrum, continuum, emission spectrum and absorption spectrum, and establish the following points. • A heated vapour (e.g. in a gas discharge tube) can produce an emission line spectrum containing just a few discrete colours/wavelengths/frequencies.
• The wavelengths can be measured using a diffraction grating. • Each element has its own distinct line spectrum. • If continuum radiation shines through a vapour, an absorption line spectrum is produced. • The wavelengths present in an emission line spectrum are the same as those absent in the absorption line spectrum of the same element.
Using line spectra Prepare a PowerPoint presentation to explain to students how line spectra can be used to deduce the elements present in a substance that can only be observed from a distance. Include the following examples along with any others that you are able to find. • During steel processing, the spectrum of light emitted by the hot molten metal provides information about the relative proportions of elements present. Further ingredients can then be added to produce a steel with a precisely determined composition. • Continuum emission from the hot surfaces of stars passes through the overlying cooler gases, giving rise to absorption spectra that indicate the elements present in the star’s atmosphere. (Point out that helium was first identified in the Sun’s spectrum, hence its name derived from the Greek helios = Sun.) Explaining line spectra With the whole class, discuss how line spectra can be explained. Use suitable questioning to establish that the atoms of a given element can only emit or absorb certain wavelengths, which implies that only photons of certain energies can be emitted or absorbed. Hence the energy of each atom must be quantised. Tell students that these energy changes are associated with changes in the way electrons orbit the nucleus. Point out the similarities between orbiting electrons and orbiting planets: a change of orbit is associated with changes in kinetic and potential energy.
561 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.6 | Physics 6 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
Introduce the concept of energy levels and show how they can be represented diagrammatically. Remind students that the electronvolt is a convenient unit for expressing small energies. Display a large clear diagram of the energy levels of a hydrogen atom on the board or OHP. Show how the levels can be labelled in J and/or eV, and point out that the highest level indicates ionisation of the atom. Point out that photon emission and absorption gives information only about the differences between energy levels, not their absolute values, so energy-level diagrams are sometimes labelled with zero at the ground state (giving all other levels positive values) and sometimes with zero at the top, corresponding to a free electron and a positive ion, so that all levels corresponding to a bound electron have negative energies.
Allocate each student two different pairs of energy levels and get them to calculate the energy differences between the two and hence deduce the frequencies and wavelengths of the hydrogen line spectrum. Tell students to write their results in a large grid on the board or OHP, with rows and columns headed 1, 2, 3, etc., to indicate the initial and final energy levels. Students should appreciate that in addition to the visible lines (which involve transitions between the second and higher energy levels) hydrogen has spectral lines in the UV and IR parts of the electromagnetic spectrum. Finally point out that the analysis of line spectra involves using both wave and photon models of light: the wave model is needed when measuring the wavelengths, whereas the photon model is needed when relating the spectral lines to energy changes within an atom.
5 hours Properties of the electron The electron Divide the class into three groups and allocate one group to each of the following topics: Enquiry skills 12A.1.4, 12A.1.5, 12A.1.8, 12A.2.1, 12A.2.2, 12A.2.4, 12A.2.5, 12A.3.1, Show an understanding of • measuring e/m for electrons; the quantisation of electronic • Millikan’s experiments to determine electron charge; 12A.3.4, 12A.4.1, 12A.4.2 charge as demonstrated, for • electron diffraction. example, by Millikan’s Ask each group to research and prepare a presentation for the rest of the class. Each ICT opportunity: Use of the internet. experiment. presentation should include at least one demonstration, one example of a historical document Safety: When using EHT supplies ensure that Show an understanding of relating to the original research, and a handout summarising key points for distribution to the internal safety resistors are connected and that wave–particle duality in the rest of the class. Depending on class size, the groups could be subdivided so that, for example, no-one can come into electrical contact with properties of the electron. some students rehearse demonstrations while others produce the handouts. the terminals. Provide a briefing sheet for each group to indicate useful sources of information, including Prepare suitable briefing sheets. textbooks and Internet sites. Allow plenty of time for preparation and rehearsal. Spend time with each group showing them how to use the apparatus for demonstration and ensuring that they know the relevant physics. Discuss the following points with the relevant group while they prepare their presentations. Measuring e/m Explain how the expression for electromagnetic force on a current (F = BIl sinθ ) can be used to show that the electromagnetic force on a single particle is F = Bqv sinθ. Discuss how deflection plates and Helmholtz coils can be used to provide opposing electrostatic and electromagnetic forces on an electron beam in a cathode-ray tube.
562 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.6 | Physics 6 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
Show how the magnetic field on the axis of Helmholtz coils can be measured or calculated. Discuss how experimental measurements can be combined to yield a value for e/m. Establish that, historically, interpretation of the experiment implied a particle model for cathode rays. Millikan’s experiments Establish that a fine spray of oil drops can become charged by friction. Show how opposing electrostatic and gravitational forces can suspend a charged oil-drop at rest. Discuss how the weight of an oil drop can be determined from measurements of its terminal velocity as it falls in air. Discuss how Millikan’s measurements provided evidence for the quantisation of charge and led to a value for the size of the charge quantum, e. Point out that Millikan has been criticised for selective interpretation of his results. Electron diffraction Show how an electron beam produces a diffraction pattern when passing through a thin layer of graphite. Discuss how the structure of graphite enables it to act as a diffraction grating. Establish that the results can be interpreted only if the electron beam is assumed to have wave- like properties. Introduce the term de Broglie wavelength. Discuss how varying the accelerating pd affects the wavelength of the electron beam. Establish that the wavelength varies inversely with the square root of the accelerating pd. Discuss how the pd is related to the electrons’ kinetic energy and hence to their momentum. Show that the wavelength λ is inversely proportional to momentum p and introduce the expression λ = h ⁄ p.
Wave–particle duality When all three groups have made their presentations, discuss them with the class and establish that, just as there are two ways of modelling the behaviour of light, so there are two ways of modelling the behaviour of electrons. Introduce the term wave–particle duality and point out that
all particles have a de Broglie wavelength, not just electrons. Explain the operation of an electron microscope and establish that, while a particle model is needed to explain the initial acceleration, a wave model is required in order to explain the production of an image. Extend the discussion of wave–particle duality to include electromagnetic radiation. By suitable questioning, guide students to the conclusion that photons have momentum p = h ⁄ λ. Explain how this gives rise to a measurable radiation pressure, which might one day be exploited in interplanetary solar sails. Provide plenty of examples that allow students to practise using concepts and equations relating to wave–particle duality.
563 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.6 | Physics 6 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
2 hours Quantisation of energy levels Electrons in atoms Refer to previous work on line spectra and the properties of the electron in a discussion with the whole class. Explain atomic spectra and permitted electron orbitals in Establish that the existence of line spectra provides important evidence of quantisation of terms of the quantisation of energy and discuss how an understanding of wave-like electron properties can be related to the
angular momentum. quantisation of energy levels.
Know how the Schrödinger Demonstrate standing waves on a stretched string and ask suitable questions to remind model for the hydrogen atom students of their work on standing waves and resonance from earlier grades. Extend the
leads to the concept of discussion to include electrons, and hence establish that an electron in a confined space can discrete energy states for only have certain sizes of de Broglie wavelength. Discuss the simple example of an electron in electrons and to the idea of a one-dimensional box with infinitely high sides: there must be a node at each end and hence the probability of finding an there must be a whole number of half-wavelengths within the box. electron at any point (related Point out that, while not in a simple box, an electron within an atom is in a confined space, and to the square of the amplitude hence its de Broglie wavelength can only take certain values. Students should appreciate that of the wave function) and the electron’s momentum and hence its energy must also be restricted to certain values hence to the concept of (i.e. there must be quantisation). ‘electron clouds’. Bend a piece of springy wire about 50 cm long into a circle and attach it to a vibration generator so that the circle is vertical. Demonstrate standing waves on the ring. Students should be able to appreciate that these occur only at frequencies that allow a whole number of wavelengths to fit around the circumference of the circle. Tell students that the de Broglie waves of electrons within atoms must also fit around the circumference of a circle and hence there are only certain allowed orbitals. Using suitable diagrams on the board or OHP, explain how the wavelength of a circular electron standing wave in an atom is related to the electron’s momentum. Introduce the term angular momentum, L, for a particle in circular orbit radius r and show that L = mvr = mr2ω, where ω is the angular velocity. Hence establish that the permitted electron orbitals can be explained in terms of the quantisation of angular momentum. Quantum mechanics Enquiry skills 12A.1.8, 12A.2.1, 12A.2.6 Introduce the term quantum mechanics and tell students that, loosely, it is the branch of physics that deals with wave models of matter and radiation and the quantisation associated with such models. Discuss with students some of the conceptual and philosophical difficulties associated with the interpretation of quantum mechanics. For example, discuss double-slit interference and the problem of reconciling wave and photon models of radiation: any experiment to determine the path of individual photons destroys the interference pattern. Remind students that the intensity of a light or sound wave is proportional to the square of its amplitude. In the photon model, the intensity is proportional to the number of photons arriving in a given time. This leads to a useful way of bringing together the wave and photon models: the probability of a photon arriving at a point is proportional to the square of the wave amplitude at that point.
564 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.6 | Physics 6 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
Tell students that waves associated with electrons and other particles can also be interpreted in terms of probability. Introduce the ideas underlying the Schrödinger equation: if it is known how a particle’s potential energy varies with position, it must also be possible to deduce how its kinetic energy and hence its momentum vary with position. This in turn shows how its wavelength must vary with position. Demonstrate a wave of variable wavelength by holding a chain or thick cord so that it hangs vertically, then oscillate the top sideways so as so set up a standing wave with at least two nodes: as the tension decreases going down the chain, the wave velocity and wavelength also decrease. Refer to the previous demonstrations of standing waves and point out that the one-dimensional model of an electron wave around a circle is a simplification, as an electron in an atom occupies a three-dimensional space. Tell students that the Schrödinger equation describes a three- dimensional wave. Tell them that, in a hydrogen atom, the equation has solutions only for certain values of the electron energy, and these correspond to the permitted energy levels deduced from measurements on line spectra. In each of these solutions, there is one radius at which the wave amplitude reaches a maximum: this corresponds to the radius at which the electron is most likely to be found. Explain that it is not possible to say precisely where the electron is at any one time, and hence explain the concept of electron clouds, which relate to the probability of finding an electron. To consolidate their work in this section, ask all students to read at least one passage from a book or website describing wave–particle duality as it relates to electrons or photons, and to make notes on the following points. • Does the author say that wave–particle duality comes from theory, experiment or both? • Does the author discuss randomness and probability? If so, how do they relate these to the observed behaviour of photons or electrons? • How does the author relate events on a very small scale (individual photons or electrons) to what we observe on a large scale? • What does the author say about the way we describe electrons or photons? Do they use words such as ‘model’ or ‘analogy’?
565 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.6 | Physics 6 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
2 hours E = mc2 2 Light, energy and matter Display the equation E = mc on the board or OHP and ask students what they already know Enquiry skills 12A.2.1, 12A.2.4, 12A.2.5 about it: they will almost certainly recognise it and might be able attribute it to Einstein. Show an understanding of the interconversion of matter Tell students that Einstein derived the equation while he was trying to understand aspects of and energy and use the light and electromagnetism, and that it forms part of his special theory of relativity published in equation E = mc2 and 1905. recognise that this explains Explain that the equation describes the interconversion between mass m and energy E. Draw the phenomenon of nuclear attention to the revolutionary nature of this relationship: in everyday life, and so far in their study energy. of physics, students treat matter and energy as completely different entities. Point out that, for many years after its publication, the equation was thought to be a meaningless by-product of the theory of relativity which sets out the equations of motion for objects travelling close to the speed of light, c. Prepare and present to the class a series of PowerPoint slides giving examples of the interconversion of matter and energy, illustrated with appropriate photographs and diagrams. Suitable examples include the following. • The creation of subatomic particles in high-energy collisions (e.g. in cosmic rays, in particle physics experiments). • The annihilation of particles and antiparticles (e.g. electron annihilating a positron) to produce electromagnetic radiation. • Nuclear processes: the slight loss of mass and its relationship to the increase in kinetic energy. Nuclear energy Introduce and explain the terms mass defect and binding energy. Display a chart showing how binding energy per nucleon varies with atomic number and discuss how its shape relates to nuclear fission and fusion reactions. Using suitable questioning, guide students through a ‘thought experiment’ in which a heavy nucleus is first separated into its individual nucleons (requiring an energy input) then reassembled into two smaller nuclei (releasing more energy than was initially supplied). Establish that, in order for energy to be released, the total mass of products must be less than the total mass of reactants, and hence that energy is released in the fusion of light nuclei and in the fission of heavy nuclei. Provide several examples that allow students to practise using E = mc2 in the context of nuclear energy.
566 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.6 | Physics 6 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
Understanding light To consolidate and extend students’ work in this unit on the nature of light, ask them to produce ICT opportunity: Use of the Internet. a timeline chart showing how ideas about light and other parts of the electromagnetic spectrum have developed since the eighteenth century. They should include the following developments Enquiry skills 12A.1.8, 12A.2.1, 12A.2.4– and should use the Internet and library resources to find the approximate date and the names of 12A.2.6 key people involved in each case. • Studies of the photoelectric effect indicate that light is quantised. • Particle–antiparticle annihilation is observed to produce gamma radiation. • Experiments establish that light can exert a pressure. • Einstein’s theory of special relativity proposes that light always travels at the same speed relative to any observer. • Double-slit interference is explained in terms of probability waves. • Interference experiments demonstrate the wave nature of light.
• Measurements of radioisotopes establish that mass and energy are interrelated through the speed of light. • It is proposed that photons have momentum.
567 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.6 | Physics 6 © Education Institute 2005 Assessment Unit 12AP.6
Examples of assessment tasks and questions Notes School resources
Assessment Radiation of wavelength 410 nm shines onto a metal with work function 1.2 × 10–19 J. What is Set up activities that allow the maximum possible kinetic energy of the photoelectrons? students to demonstrate what Electron charge e = 1.60 × 10–19 C, Planck constant h = 6.63 × 10–34 J s. they have learned in this unit. In part of an electron energy level diagram for mercury, the ground state is labelled –10.4 eV, The activities can be provided and there are higher states labelled –5.5 eV and –5.0 eV. informally or formally during and at the end of the unit, or a. Draw a diagram to represent these energy levels. for homework. They can be b. Write down the energies of the photons that could be emitted or absorbed in transitions selected from the teaching between these levels. activities or can be new c. Calculate the shortest wavelength of radiation that could be emitted in these transitions. experiences. Choose tasks d. Explain why the levels are all labelled with negative energies. and questions from the examples to incorporate in In each of the following situations, say whether you would use a wave model or a photon model
the activities. of electromagnetic radiation to explain what happens. Give reasons for your decisions. a. Light shines onto a wall through two closely spaced narrow slits and produces a series of bright spots. b. Light stimulates the cells in the retina of your eye so that you see different colours. c. Gamma radiation produces a series of ‘clicks’ in a Geiger counter. d. A radio receiver picks up signals direct from the transmitter and reflected from a nearby building; the two interfere to give a resultant that is weaker than either signal on its own.
Explain how Millikan’s experiments enabled the electron charge to be determined.
Electrons are accelerated from rest through a pd of 5000 V. What is their resulting de Broglie wavelength?
Write a short article for an encyclopaedia explaining the term wave–particle duality.
An isotope of plutonium absorbs a neutron and undergoes nuclear fission:
239 1 145 93 94Pu+→ 0 n 56 Ba + 36 Kr Using the data listed below, calculate the energy released.
239 94Pu : m = 239.052 17 u 1 0n : m = 1.008 665 u 145 56Ba : m = 144.926 94 u 93 36Kr : m = 92.931 12 u 1 u = 1.661 × 10–27 kg speed of light c = 3.00 × 108 m s–1
568 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.6 | Physics 6 © Education Institute 2005 GRADE 12A: Physics 7 UNIT 12AP.7 15 hours Astrophysics and cosmology
About this unit Previous learning Resources
This unit is the seventh of seven units on physics To meet the expectations of this unit, students should already know that The main resources needed for this unit are: for Grade 12 advanced. each element give rise to its own characteristic line spectra, that • binoculars The unit is designed to guide your planning and electromagnetic radiation travels through space at finite speed, and that • planisphere or star map relative motion between an observer and wave source gives rise to the teaching of physics lessons. It provides a link • materials for making scale models (e.g. fruit, marbles, sand) Doppler effect. They should know that all matter is affected by gravitational between the standards for science and your • tennis ball and table-tennis ball lesson plans. force. They should also know that stars are powered by nuclear fusion reactions that lead to the production of heavier elements. The teaching and learning activities should help you to plan the content and pace of lessons. Key vocabulary and technical terms Adapt the ideas to meet your students’ needs. Expectations Students should understand, use and spell correctly: For consolidation activities, look at the scheme of • constellation, nebula, star, planet work for Grade 11A. By the end of the unit, students know how emission and absorption spectra yield information about distant stars and galaxies. They explain the • luminosity, intensity, flux You can also supplement the activities with structure of the visible Universe in terms of the gravitational attraction • Hertzsprung–Russell (HR) diagram appropriate tasks and exercises from your between objects. They define and use the parsec and the light-year. They • light-year, astronomical unit, parsec school’s textbooks and other resources. explain the creation and evolution of stars and know how their ultimate fate • galaxy, Milky Way Introduce the unit to students by summarising depends on their mass. They know how elements are formed in stars and • red giant, white dwarf, black hole, neutron star, pulsar what they will learn and how this will build on how planetary systems arise. They know the ‘big bang’ theory of the origin of • dense cloud, supernova remnant, planetary nebula earlier work. Review the unit at the end, drawing the Universe and can adduce evidence for it. out the main learning points, links to other work • protostar, main sequence, supernova Students who progress further know how a Hertzsprung–Russell diagram and real world applications. • accretion disc, stellar wind, exoplanet, evolutionary track can be used to summarise properties of stars and to represent changes as they evolve. They are aware of the evidence on which current theories of • redshift, Hubble’s law, Hubble constant, big bang star formation and the big bang are based. They understand the importance • open universe, closed universe, critical density of gravity in determining the ultimate fate of the Universe and know how the Universe can be, at the same time, finite but without boundaries.
569 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.7 | Physics 7 © Education Institute 2005 Standards for the unit Unit 12AP.7
SUPPORTING STANDARDS CORE STANDARDS EXTENSION STANDARDS 15 hours Grade 12 standards
3 hours 11A.29.3 Use a diffraction grating to show ... 12A.30.1 Distinguish between emission and absorption spectra; know how these can visible spectra … provide information on the elements present in stellar objects and how far Measuring the away the objects are. stars 11A.29.4 Explain the Doppler effect in terms of wave motion and give examples from 4 hours sound and light. Galaxies 12A.25.4 Recall and use Newton’s law of 12A.31.1 Describe, and explain in terms of gravitational attraction, the structure of universal gravitation in the form the visible Universe today and know that our Sun is a star in the Milky Way 2 F = G(m1m2)/r and relationships galaxy. 4 hours derived from it. Stars and planets 11A.29.6 ... know that all electromagnetic 12A.31.2 Know why powerful telescopes allow us to look back in time to when the
waves travel with the same velocity Universe was much younger than it is now. 4 hours in free space …
Modelling the 12A.31.3 Show an understanding of the size and number of stars and galaxies, the Universe distances between them, and the size of the Universe. Know and define the size of the light-year and the parsec.
11A.32.6 Know the source of energy in stars, 12A.31.4 Know how stars are created, that they are made mainly from the element including the Sun. hydrogen and that their ultimate fate depends on their size and can lead to 11A.32.7 ... know how heavier elements are supernovae, white dwarfs, neutron stars (pulsars) or black holes. formed in older stars by nuclear fusion. 11A.32.2 ... use the common notation for 12A.31.5 Explain the process of element formation in stars and know how this leads representing nuclides and write to the generation of energy. equations representing nuclear 12A.31.6 Describe the process of planet formation by gravitational attraction from the transformations. remains of an older exploded star. 12A.31.7 Know that current thinking favours the ‘big bang’ model of the Universe, 12A.31.8 Understand how the Universe can at which postulates that all matter, time and space were created in a ‘big the same time be finite but have no bang’ around 14 billion years ago, and that since then the Universe has boundaries. been expanding.
570 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.7 | Physics 7 © Education Institute 2005 Activities Unit 12AP.7
Objectives Possible teaching activities Notes School resources
4 hours Observing the sky Use this column to note your own school’s Measuring the stars Either arrange an evening for the whole class to meet and observe the night sky, or brief Safety: Ensure that students observe only from resources, e.g. ... know how [line spectra] students so that they can make observations in their own time. safe locations. textbooks, worksheets. can provide information on Using a planisphere, or a star-map downloaded from the Internet, identify some easily Enquiry skill 12A.1.8
the elements present in recognisable constellations (e.g. Orion, the Plough) that will be visible in the night sky at the stellar objects and how far time and location of students’ observations. Students should use binoculars to study the stars in
away the objects are. these constellations, noting their different colours and brightnesses. Introduce the term nebula, Show an understanding of meaning, loosely, an object that appears extended and fuzzy; if possible students should also the size and number of stars observe the Orion and Andromeda nebulae and note how they differ from stars. Students and galaxies, the distances should also observe any planets that are visible at the time of their observations. between them, and the size Colour and brightness of the Universe. Know and Discuss students’ observations from the previous activity and ask them to suggest reasons for define the size of the light- the different colours and brightnesses of stars. year and the parsec. Show students a radiant heater warming up: as it gets hotter, its colour changes from a dull red
glow to bright orange. Show a filament lamp connected to a variable power supply: when the
filament is cool it glows faintly red, but when it is hotter it becomes yellow-white and brighter. Display black-body radiation graphs on the board or OHP and establish that temperature can be deduced from observations of the relative amounts of radiation in two or three parts of the electromagnetic spectrum.
Refer to students’ observations of stars and ask them to say which of the stars they observed
are the coolest and which the hottest.
Ask students to suggest reasons for the different observed brightnesses of stars. Introduce the
term luminosity, meaning the total power radiated by a star, and by suitable questioning establish the following points. • If two stars are the same size, the hotter one will emit more radiation in all parts of the spectrum (i.e. it is more luminous). • If two stars are the same temperature, the larger one will emit more radiation as it has a larger surface (i.e. it is more luminous). • If two stars are the same size and temperature, they have the same luminosity, but the closer one will appear brighter. Introduce the terms intensity and flux F to mean the received radiant power per unit area. Demonstrate that the intensity of light from a torch bulb shining onto a screen diminishes with distance, and use suitable diagrams to show that the intensity of radiation from a point source obeys an inverse-square law. Provided there is no absorption or scattering of radiation en route, F = L ⁄ 4πd2, where d is distance. Ask students to say which of the stars they observed are likely to be the closest and which the most distant.
571 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.7 | Physics 7 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
Let students use the Internet to find information about the sizes, distances and temperatures of ICT opportunity: Use of the Internet. the stars they have observed. Tell them to rank the stars in order of temperature and of In their search for information, students may distance, and to compare these rankings with their predictions of relative temperature and come across the term magnitude. Explain that distance. They should note the units used to express distances; even if these are unfamiliar, apparent magnitude is related to observed they should still be able to produce a rank order for their observed stars. brightness, while absolute magnitude is related to luminosity. Tell students that the magnitude scale relates to visual perception, so stars that appear brightest are ranked as ‘first magnitude’ while those that appear fainter are ranked second, third and so on. Enquiry skill 12A.1.8
Luminosity of the Sun Ask students, working in pairs, to use a simple oil-spot photometer to estimate the Sun’s Safety: Students should not look directly at the luminosity as follows. Sun. • Use a compass needle or similar to place a small drop of cooking oil on a sheet of white Enquiry skills 12A.1.1, 12A.1.3, 12A.1.5 paper (the spot produced should be as small as possible). • Arrange the paper so that light from an unshaded filament lamp of known luminosity (e.g. 100 W) shines onto one side, and sunlight onto the other. • Adjust the position of the paper so that the oil spot appears to merge into the surrounding paper: the intensities of illumination from the two sources are then equal. • Measure the distance from lamp to paper and use the known Earth–Sun distance to calculate the Sun’s luminosity using the inverse-square law. Encourage students to discuss sources of inaccuracy in this method and to suggest improvements. They should also consider how results might be affected by atmospheric absorption of sunlight, and by the difference in temperature of the two light sources. The HR diagram Display a large Hertzsprung–Russell (HR) diagram. Ideally this should have luminosity plotted on the y-axis and temperature on the x-axis. If you use a version with axes showing magnitude and colour index, explain to students that these quantities are closely related to luminosity and
temperature. Point out the use of logarithmic scales and the convention for labelling the x-axis so that temperature increases from right to left. Also point out that temperature is expressed in kelvins, while luminosity can be expressed either in its SI units (watts) or in terms of the Sun’s luminosity LSun. Draw attention to the diagonal band known as the main sequence, on which most stars lie. Ask students what they can deduce about stars lying in the upper right-hand and lower left-hand regions of the diagram. By suitable questioning, establish that stars in the upper right are cool luminous stars: tell students these are called red giants. Similarly, establish that stars in the lower left are hot stars with low luminosity known as white dwarfs.
572 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.7 | Physics 7 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
Distance units Refer to the previous activities and ask students if they found any unfamiliar non-SI units being used to express distances: they will probably have come across the light-year and parsec. Establish that the light-year (ly) is the distance light (and other electromagnetic radiation) travels through space in 1 year. Ask students to calculate the number of seconds in a year and then
use the speed of light to calculate the size of one light-year.
Use suitable diagrams on the board or OHP to introduce and define the astronomical unit (AU). Mathematics: This activity requires a Show how the size of the parsec (pc) is related to the AU and explain that a star at 1 pc from knowledge of the trigonometry of right-angled Earth has an annual parallax of 1 arcsec: as the Earth moves once around its orbit, the star triangles, angles expressed in arcsec and appears to move through an angle of 1 arcsec either side of its central position relative to the radians, and the small-angle approximation. background of more distant ‘fixed stars’. Tell students that the size of the AU is well established through radar measurements within the Solar System, hence the size of the pc is also well known. Students should use trigonometry and the small-angle approximation to calculate the size of the pc using 1 AU = 1.50 × 1011 m. Provide plenty of examples that allow students to practise calculations involving conventional non-SI units for astronomical distances. Point out that parallax measurements can only be used for relatively nearby stars (closer than about 100 pc). For more distant stars, less direct methods must be used. Explain how the HR diagram can be used in the following ways to estimate distances of stars. • Single star. Deduce the star’s temperature from its colour. Assume the star lies on the main sequence and use the HR diagram to deduce its luminosity. Measure the flux received at Earth and calculate its distance using the inverse-square law. This method can be refined: stars of the same temperature but different luminosity can be distinguished by subtle differences in their line spectra, removing the need for the initial assumption. • Cluster of many stars. Determine the temperature and flux of each star. Plot an HR diagram for the cluster of stars using flux instead of luminosity. Superimpose this plot on a standard HR diagram, aligning the temperature scales, and hence deduce the relationship between luminosity and flux for the cluster. Ask students to write a short account of methods for measuring stellar distances.
573 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.7 | Physics 7 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
4 hours Observing galaxies Galaxies Prepare and present a series of PowerPoint slides showing images of galaxies downloaded Prepare a PowerPoint presentation. Describe, and explain in from the Internet and illustrating the following points. 8 12 terms of gravitational • A galaxy is a large collection of stars (typically 10 –10 stars) bound together by mutual attraction, the structure of the gravitational attraction. visible Universe today and • Many galaxies have the shape of thin discs with bright stars concentrated into spiral arms, but know that our Sun is a star in the majority are featureless ellipsoidal collections of stars and some are irregular in shape. the Milky Way galaxy. • The faint band of light across our sky, known as the Milky Way, is the light of many distant Know why powerful stars lying in a thin disc. telescopes allow us to look • The Milky Way is a spiral galaxy, and the Sun lies about two-thirds of the way out from the back in time to when the centre. Universe was much younger • The nearest major galaxy to the Milky Way is the Andromeda galaxy (Andromeda nebula), than it is now. which is also a spiral. Show an understanding of • Even the nearest galaxy lies at a distance of a few million light-years. Light reaching us has the size and number of stars been in transit for this time, so it carries information about the galaxy as it was a few million and galaxies, the distances years in the past. between them, and the size • Galaxies are found to be grouped into clusters, bound by gravity. A large cluster might of the Universe. Know and contain thousands of galaxies. define the size of the light- • Powerful telescopes observing at great distances reveal that there are some regions of the year and the parsec. Universe with many clusters of galaxies and others, known as voids, with very few clusters. • Even the nearest galaxies lie far beyond the reach of the stellar distance measurement techniques discussed in the previous section.
Measuring distances of galaxies Divide the class into three groups and set each group the task of using the Internet and library ICT opportunity: Use of the Internet. resources to research one of the following methods for determining distances to galaxies: Enquiry skills 12A.1.4, 12A.1.6, 12A.1.8, 12A.3.4 • Cepheid variable stars; • planetary nebulae (planetary nebula luminosity function, PNLF);
• Type Ia supernovae.
If the groups are large, subdivide them so that several small groups research the same method. Ask each small group to prepare an A3 poster containing the following information: • details about the type of object used and how such objects can be identified from observations; • a note of the measurements that must be made and how they can be used to deduce distance; • some information about the first use of the method (e.g. who was responsible, when and where they worked); • the largest distances that can currently be deduced using this method; • an image of a galaxy whose distance has been determined using this method; • a note of the information sources consulted. Display the posters around the lab and allow time for students to read one another’s work. Students should then each produce their own written summary of all three methods.
574 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.7 | Physics 7 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
Scale mapping and modelling Divide students into small groups and challenge them to design and produce a map or a scale ICT opportunity: Use of the Internet.
model that can be used to help younger students (e.g. Grade 9) appreciate the sizes and Enquiry skill 12A.3.4 distances involved in astronomy. They should consult the Internet and other resources to obtain
any information about size and distance that they need. Suitable tasks include the following. • Solar System. Make a model that shows the relative sizes of planets using everyday objects (e.g. fruit, marbles, footballs). • Stars. Make a map or a model that shows typical sizes and separations of stars in our region of the Milky Way (e.g. if the Sun and the nearest star are represented by marbles, how far apart should they be?). • Milky Way. Devise a way to show the size and shape of the Milky Way and the number of stars it contains (e.g. if each star is represented by a grain of sand, how much sand would you need to represent the whole galaxy?). • Galaxies. Make a model to show the so-called local group of galaxies, which includes the Milky Way (e.g. if the Milky Way and the Andromeda galaxy are represented by paper discs 10 cm in diameter, how far apart should they be?). If possible, arrange for students to display and talk about their models to younger students. In any case, display them where they can be seen by other members of the school (e.g. in a corridor, hall or playground).
4 hours Star formation Stars and planets Display a star map and an HR diagram and point out that they are static records of stars as we ... know how [line spectra] currently observe them. Tell students that the main sequence was initially thought to represent an evolutionary sequence (hence the name) showing a gradual change in stellar temperature can provide information on the elements present in with time. When it became possible to deduce the masses of stars (by observing their
stellar objects ... gravitational effects on one another) it became clear that hot main-sequence stars had much greater masses than cool main-sequence stars, and there was no evidence of any processes Know how stars are created, that could account for significant changes in stellar masses with age. Discuss with students the that they are made mainly difficulties facing astrophysicists trying to deduce how stars function, how they are formed and from the element hydrogen how they change over time: the only information available comes from observations of distant and that their ultimate fate objects which, with a few exceptions, remain unchanged over human timescales. Discuss the depends on their size and analogous problem of trying to deduce, from a snapshot of people in a city street, how human can lead to supernovae, beings develop and change with age. white dwarfs, neutron stars (pulsars) or black holes. Students should be able to appreciate that the HR diagram indicates the existence of certain stable combinations of stellar luminosity and temperature: many stars are observed to lie on the Explain the process of main sequence, or in the red giant or white dwarf regions of the diagram, which suggests that element formation in stars these represent long-lasting phases in a star’s life (just as a photograph in a city street shows and know how this leads to more people of adult size than children). Point out that our current picture of star formation has the generation of energy. been developing since the early twentieth century, and is based on results of stellar observation Describe the process of planet and Earth-based laboratory research, which have been brought together to build a picture that formation by gravitational is consistent with the available evidence. attraction from the remains of an older exploded star.
575 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.7 | Physics 7 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
Prepare and present a sequence of PowerPoint slides to establish the following points. Prepare a PowerPoint presentation. • Stars are powered by nuclear fusion in their cores. This requires high density and temperature. • Within a galaxy, there is gas and dust (small solid particles) lying between the stars. This interstellar material (ISM) includes warm glowing clouds of gas and cool denser clouds. Even the so-called dense clouds are extremely tenuous: on Earth they would be classed as vacuum. • The temperature, density and composition of interstellar clouds can be deduced from the radiation they emit and from the absorption they produce in starlight shining through them. • The surface composition of stars can be deduced from their line spectra. • Stars and ISM are predominantly made from hydrogen and helium, with traces of other elements. • A challenge of astrophysics is to explain how cold tenuous ISM can become hot and dense enough to sustain nuclear fusion and form a star. • Another challenge is to account for the predominance of heavier elements making up the Earth and other planets. • Theory and observation indicate that star formation takes place in clouds that gradually collapse under their own gravity. For this to happen, the cloud must be dense and massive (many times the Sun’s mass) so that internal gravitational forces are strong, and cold so that random thermal motion does not disperse the cloud. • During collapse, material falling towards the centre of the cloud gains kinetic energy. The random thermal motion of particles is increased (i.e. the material gets hotter). • As a cloud collapses, it fragments into locally collapsing regions, which become main- sequence stars. • Around each newly formed star there remains a disc of gas and dust, from which planets form by gravitational attraction. • Close to the star, where temperatures are high, volatile materials made up of hydrogen and other light elements are unable to condense and are driven outwards. Planets close to the star contain a large proportion of heavy elements, while those further out are composed largely of hydrogen and helium. Evidence for star and planet formation Ask students to work in pairs or individually to collect evidence relating to the formation of stars ICT opportunity: Use of the Internet. and planets. As part of this task they should look for the following items in books or on the Enquiry skills 12A.1.4, 12A.1.6, 12A.1.8, 12A.3.4 Internet and use scientific dictionaries or websites to find the meanings of the key terms in italic.
• Images showing infrared emission from warm protostars within the Orion nebula.
• Images of accretion discs around stars. • Observations of stellar winds. • Data relating to the composition of Solar System planets. • Data showing the motion of gas and dust around newly formed stars. • Graphics or animations showing the evolutionary track of a protostar on an HR diagram. • Data indicating the existence of exoplanets. Students should download, or photocopy, relevant images and information in order to compile their own accounts of star and planet formation.
576 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.7 | Physics 7 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
End points of stellar evolution Use a combination of presentation, images, demonstration and questioning to establish the following points about the end points of stellar evolution. • A star with mass up to about 8 M will reach a point when collapse under its own gravity Sun does not produce a high enough temperature to initiate the next stage of fusion. The abrupt halt of fusion causes ejection of the star’s outer layers, which expand to produce a tenuous
shell of glowing gas known as a planetary nebula. The core is less than about 1.4 MSun and becomes a white dwarf.
• Stars with mass greater than about 8 MSun can produce elements up to iron in their cores. Further stages of nuclear fusion are endothermic, so there is no release of energy or build-up of pressure to prevent further gravitational collapse. • The runaway collapse of a massive star core gives rise to a stellar explosion known as a supernova as the outer regions go into free fall then bounce outwards. (Place a table-tennis ball on top of a tennis ball. Drop them both together, taking care to release them vertically so that they remain in contact as they fall; like the outer layers of a collapsing star, the table tennis ball rebounds to many times its original height.) • During a supernova explosion, heavier elements are synthesised, and most of the star is ejected into space along with a vast output of electromagnetic radiation. • The ejected material forms a supernova remnant: a cloud of expanding, glowing gas. It gradually cools and might eventually be able to collapse and form new stars and planets. • The remaining central part of the star continues to collapse under its own gravity. Electrons and nuclei are forced very close together and the protons and electrons combine to produce neutrons.
• If the central remnant is less than about 2.25 MSun, the formation of neutrons prevents further collapse and it becomes a neutron star. Some neutron stars are observed as pulsars; they spin rapidly and emit narrow beams of radiation that we detect as short pulses each time they point towards Earth. (Mount a torch on a rotating turntable so that it points horizontally. In a darkened room, rotate the turntable so that students see the torch appear to flash as it points towards them.)
• If the central remnant is more massive than 2.25 MSun, it continues to collapse under its own gravity to become a black hole. Close to a black hole, the gravitational field is so strong that not even light can escape. Ask students to work individually or in pairs to draw a flow chart summarising the stages in a Enquiry skill 12A.3.4 star’s evolution, starting from the main sequence, showing how its mass influences the outcome of each stage.
577 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.7 | Physics 7 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
Stellar end points Students should work in pairs or small groups to find more information about the ways stars ICT opportunity: Use of PowerPoint; use of the come to an end. They should download relevant images and produce about ten PowerPoint Internet. slides on their topic for presentation to the rest of the class. Suitable topics include the following. Enquiry skills 12A.1.6, 12A.1.8, 12A.2.2, 12A.2.4 • Historical observations of Milky Way supernovae such as those observed in 1006, 1054,
1181, 1572 or 1604: where in the sky each was observed, and from where the observations were made. Students should suggest why these spectacular events were only noticed in a few locations. • Remnants of historical supernovae: modern images and data relating to events such as those listed above. • Supernovae observed in other galaxies, including the one observed in the nearby Large Magellanic Cloud galaxy in 1987. • The object known as Eta Carinae. • The discovery of pulsars: when and how they were discovered, and how the observations were initially interpreted. • Hubble Space Telescope observations of planetary nebulae. • Evidence for black holes: if no matter or light can escape, how can such objects be detected?
Compact objects Produce sets of cards, each of which contains one statement, image or piece of information Prepare suitable sets of cards. relating to a white dwarf, neutron star or black hole. Make at least six cards for each type of object. Suitable examples include the following: • can be observed as a pulsar; • the end-point of a Sun-like star; • the fate of the most massive stars. Divide students into groups of three to play the following game. Each group should allocate one type of object to each student, place the cards face down and turn over the top card. In turn, each student takes either the upturned card or one from the pack. If the card they pick up does not relate to their object, they should discard it face up. Continue until one person has a full set of cards for their object.
578 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.7 | Physics 7 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
4 hours Universal expansion Modelling the Universe Display a graph that plots the redshifts of several galaxies against their distance (either Hubble’s original results or some more recent data). Introduce and define the term redshift ... know how [line spectra] z = ⁄ . Remind students about line spectra and tell them that, like starlight, light received can provide information on ∆λ λ the elements present in from nearby galaxies includes lines (mainly due to hydrogen) whose wavelengths are precisely known. Light from distant galaxies is redshifted (i.e. it contains patterns of lines similar to those stellar objects and how far of nearby galaxies but at longer wavelengths). away the objects are. Describe, and explain in Divide students into pairs or small groups and ask them to brainstorm and suggest how the redshift–distance data might be interpreted. terms of gravitational attraction, the structure of the In discussion with the whole class, note students’ ideas on the board or OHP, then by suitable visible Universe today ... questioning establish the following points. Know why powerful • A galaxy’s redshift indicates its velocity relative to us. A redshift implies a recession. telescopes allow us to look • Only a few very nearby galaxies have spectral lines that are blue-shifted. Apart from these back in time to when the nearby galaxies, all other galaxies are receding from us. Universe was much younger • Redshift is proportional to distance: the more distant a galaxy, the more rapidly it is receding. than it is now. • The observations suggest that the entire Universe is expanding. Know that current thinking • Although we see all other galaxies receding, this does not imply that we are at the centre of favours the ‘big bang’ model the Universe. of the Universe, which Use animations and models to demonstrate that, in a uniform expansion, an observer on any postulates that all matter, galaxy sees all other galaxies receding with a speed that is proportional to its distance. Suitable time and space were created models include the following. in a ‘big bang’ around 14 • Stick paper dots representing galaxies onto a wide rubber band. Choose one arbitrarily to be billion years ago, and that the Milky Way. Stretching the band causes all other galaxies to recede from our galaxy. since then the Universe has • Stick paper dots representing galaxies onto the surface of a balloon. Inflating the balloon been expanding. causes all other galaxies to recede from our galaxy. Understand how the Universe • Draw several dots on an acetate sheet. Make an enlarged photocopy onto another acetate can at the same time be finite sheet. Choose one dot arbitrarily to be the Milky way and overlay the two sheets so that the but have no boundaries. two Milky Way dots coincide. Show that the other dots have receded from the Milky Way at speeds proportional to their distances.
Introduce Hubble’s law v = H0d and define the Hubble constant H0. Tell students how Hubble’s law can be used to deduce distances to galaxies: the relationship first needs to be established by measuring the distances to some galaxies using methods such as Type Ia supernovae or Cepheid variables. Then the distances to other galaxies can be deduced from their redshifts: find v, then calculate d using Hubble’s law. Tell students that, in practice, astronomers often quote values of redshift as direct indicators of distance. The big bang Refer to the previous discussion and establish that the observation of galactic recession implies that there was a time in the past when all galaxies had zero separation. Tell students that this can be interpreted in terms of a big bang: an explosion from a state of extremely high density that marks the beginning of our Universe.
579 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.7 | Physics 7 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
Point out the units of the Hubble constant. Students should appreciate that with speed and –1 distance expressed in SI units, H0 would have units s . Establish that, assuming the expansion has been proceeding at the same rate since the big bang, the age of the Universe can be
deduced from Hubble’s law: t = d ⁄ v = 1 ⁄ H0. Tell students that astronomers usually express galaxies’ recession velocities in km s–1 and their –1 –1 distances in Mpc, giving H0 in non-SI units km s Mpc . –1 –1 Students should be able to use current measurements of H0 (close to 75 km s Mpc ) to estimate the age of the Universe. Discuss the assumptions underlying this simple calculation. Students should be able to appreciate that gravitational forces between galaxies will decelerate their recession so the expansion is less rapid now than in the past. They should be able to explain how this will affect our estimates of the age of the Universe based on Hubble’s law: the time taken for galaxies to reach their present separations must be less than the simple estimate. Explain to more advanced students how the finite age of the Universe places a limit on its observable size: we cannot observe objects whose distance exceeds the distance that light has travelled since the big bang. Point out that when astronomers talk of ‘the size of the Universe’, they often mean the size of the observable Universe, which is finite, rather than size of the entire Universe, which is thought to be infinite. Evidence for the big bang Prepare and present a sequence of PowerPoint slides summarising current evidence relating to Prepare a PowerPoint presentation. the big bang. In addition to the observations of galactic recession, include the two other major items of evidence. • Abundance of elements. The big bang theory predicts that initially the Universe consisted of fundamental particles and radiation. As the Universe expanded, the particles combined. Detailed models based on our knowledge of particle reactions predict the proportions of hydrogen, helium and other elements produced in the first few minutes of the expansion, after which the density would become too low to allow further reactions. The observed abundances in interstellar space and the outer regions of stars match the predictions very closely. • Microwave background radiation. Theory predicts that radiation produced in the first few minutes after the big bang would still be travelling through space, and that as space expands so does the wavelength of the radiation. Initially, the wavelength would be very short as the matter producing it was very hot, but it has now expanded to a few centimetres. Radiation close to the predicted wavelength has been detected coming from all directions in space. • Very distant objects. Observations at high redshift involve light that has been in transit for a time that is comparable to the age of the Universe. Objects known as quasars (extremely luminous galaxies) are observed only at high redshift, indicating that they were far more common in the early Universe than now (i.e. there is evidence that the Universe has evolved over time rather than existing in a steady state). Let students discuss how current thinking about the big bang relates to their religious beliefs. Enquiry skill 12A.2.2
580 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.7 | Physics 7 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
The future of the Universe Ask students to speculate on the future of the Universe: will the expansion continue indefinitely, or will gravitational attraction eventually halt and reverse it? Display graphs showing how the separation between two galaxies will change with time in either of these scenarios. Introduce the terms open universe and closed universe. Ask students to suggest what might determine the way in which expansion proceeds. By suitable questioning, establish that the expansion will cease (i.e. the Universe will be closed) only if the average density of matter in the Universe exceeds a certain critical density. Collect magazine articles (e.g. from Scientific American) and download webpages relating to current estimates of the density of matter in the Universe and the ultimate fate of the Universe. Distribute them to students to read and discuss in small groups. Suitable topics include the following. • Estimates of the density of visible matter in the Universe (which fall far short of the critical density). • Evidence for dark matter adduced from observations of galactic rotation and the motion of galaxies in clusters. • The search for dark matter particles. • Evidence suggesting that the expansion is in fact accelerating because of a hitherto unknown force. Light and matter Using suitable visual aids, introduce more advanced students to some of the basic ideas of general relativity and how these relate to our current understanding of the Universe. Include the following points. • Einstein’s general theory introduced the notion that forces can be understood as distortions in space-time. In particular, gravity is the distortion of space-time caused by matter and it causes light to deviate from travelling in a straight line. • Observational evidence supporting Einstein’s theory was first obtained in 1919 during a solar eclipse, when stars viewed close to the Sun appeared to shift in position. • If the density of the Universe exceeds the critical density, then the space-time distortion is such that it causes light to travel around a closed path. • The geometry of a closed universe can be represented by analogy with the surface of a sphere, which is a two-dimensional surface in three-dimensional space and which is finite but without boundaries (light or anything else travelling in a ‘straight line’ actually follows a closed path). In a closed universe, our three-dimensional space is finite but without boundaries. • Similarly, the geometry of an open universe can be represented by analogy with a hyperboloidal surface, and if the Universe has critical density its geometry is analogous to that of a flat plane.
581 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.7 | Physics 7 © Education Institute 2005 Objectives Possible teaching activities Notes School resources
Theories of the Universe Point out to students that current thinking about the Universe differs from earlier ideas. Current thinking is that we inhabit a planet that orbits an unexceptional star, one of many stars (which might also have planets) in the outskirts of an unexceptional galaxy that does not occupy any particularly privileged place in the Universe, whereas in historical times people believed that the Universe was centred on human civilisation. Divide students into small groups and set each the task of researching one of the historical developments that preceded our current understanding. Suitable topics include: • Ancient Greek geocentric models; • the heliocentric models of early Islamic philosophers; • conflicts in Europe involving geocentric and heliocentric models; • the discovery of ‘island universes’. Tell students to use the Internet and library resources to research information and to pay ICT opportunity: Use of the Internet; use of particular attention to the way scientific work is influenced by the social, cultural, moral and PowerPoint. spiritual contexts in which it is undertaken. They should also note the importance of Enquiry skills 12A.1.6, 12A.1.8, 12A.2.1, technological developments, such as the telescope, and the way in which prevailing paradigms 12A.2.2, 12A.2.4, 12A.2.5, 12A.3.4 can be overthrown by observational evidence.
Ask each group to prepare a PowerPoint presentation and a handout summarising their findings for photocopying and distribution to the rest of the class. After students have given their presentations to the class, allow time for them to continue and extend their discussions from the previous activities.
582 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.7 | Physics 7 © Education Institute 2005 Assessment Unit 12AP.7
Examples of assessment tasks and questions Notes School resources
Assessment A student who is not studying science says ‘No one has ever travelled to a star. It must be Set up activities that allow impossible to know how far away they are or anything else about them.’ Write an explanation students to demonstrate what for this student describing how it is possible to deduce the temperatures and distances of stars they have learned in this unit. using Earth-based observations. The activities can be provided In a scale model, the Milky Way and the Andromeda galaxy are both to be represented by discs informally or formally during 10 cm in diameter. Given that the diameter of the Milky Way is about 30 kpc, and the and at the end of the unit, or Andromeda galaxy lies at a distance of about 2.4 million light-years, how far apart should the for homework. They can be discs be placed in the model? selected from the teaching activities or can be new Draw a sequence of labelled diagrams to show how the collapse of a cold interstellar cloud can
experiences. Choose tasks produce a main-sequence star. and questions from the Write a short account of how elements heavier than hydrogen are produced in stars and examples to incorporate in become the raw material for making planets. Include the following terms: nuclear fusion, star, the activities. supernova, gravity.
Use a simple model (e.g. paper dots stuck onto the surface of a balloon) to explain Hubble’s observation that the redshifts of galaxies are proportional to their distances.
–1 –1 Using H0 = 75 km s Mpc and assuming a constant rate of expansion since the big bang, calculate the age of the Universe. Give your answer in seconds and in years.
583 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.7 | Physics 7 © Education Institute 2005
584 | Qatar science scheme of work | Grade 12 advanced | Unit 12AP.7 | Physics 7 © Education Institute 2005