KS3 Science Home learning

Reactions 2 Name: ______Class: ______Teacher: ______In this topic you will learn about: • Exothermic and Endothermic reactions. • How to represent energy changes in reactions. • How to speed up reactions. Practical skills: • Measuring temperature changes This will prepare you for: • GCSE • GCSE Physics Maths in science: • Reading a graph • Calculating differences in temperature and energy Lesson 1: Exothermic Reactions Lesson 1: Exothermic Reactions

In and On: Look at the images on the board. Are the following physical or chemical changes?

1. Ice melting

2. Frying an egg

3. Burning magnesium

Challenge: What is the difference between a physical and chemical change?

Learning Objectives • Describe examples of exothermic reactions • Explain the energy changes taking place during an exothermic reaction

What does ‘exothermic’ mean? ______Exothermic reactions are reactions or processes that release energy, usually in the form of or ______light. In an exothermic reaction, energy is released ______because the total energy of the products is less than the total energy of the reactants. Exothermic reactions Energy changes occur in all ______. In exothermic reactions, energy is ______, usually in the form of ______. This means that the temperature of the surroundings ______.

Challenge: An example of an exothermic reaction is…. Investigating exothermic reactions Citric Acid and Baking soda Magnesium ribbon and Hydrochloric 1. Add 2cm depth of citric acid to a acid test tube 1. Add 2cm depth of Hydrochloric 2. Record temperature acid to a test tube. 3. Add 1 spatula scoop of baking 2. Record temperature soda 3. Add a few pieces od magnesium 4. Record temperature ribbon 4. Record temperature Record your observations to identify the exothermic reaction Citric acid and baking soda Magnesium ribbon and Hydrochloric acid Temperature at start (oC) 23 22

Temperature at end (oC) 10 42

Conclusion: ______Citric acid and baking soda is an endothermic reaction as ______the temperature decreases. ______Magnesium and hydrochloric acid is exothermic as the temperature increases.

Explain, using ideas about particles and atoms, why burning magnesium is an exothermic reaction. ______Burning magnesium is an exothermic reaction because ______when magnesium and particles collide to form new ______bonds, energy is released into the surroundings.

How canThis you tellreaction that this isreaction exothermic is exothermic?because the energy of the ______products is less than the energy ______of the reactants 11

the temperature increases allow gets hotter / heat / energy is given off

(energy of) products lower than (energy of) reactants Lesson 2 : Endothermic reactions

In and On: Using only addition, how can you add eight 8's to get the number 1,000? 888 +88 +8 +8 +8 =1,000 Learning Outcomes: • Describe examples of endothermic reactions • Explain the energy changes taking place during an endothermic reaction

What is the difference between endothermic and exothermic reactions? ______Endothermic reaction take in heat ______from their surroundings whereas ______exothermic reactions give out heat ______to their surroundings. ______

Practical 1: Practical 2: 1. Fill a test tube 1/3 with 1. Fill test tube 1/3 water Copper sulfate 2. Add 1 spatula of Sodium 2. Record the temperature Bicarb 3. Add a 2cm length of 3. Record the temperature magnesium ribbon 4. Add 1 spatula of Citric acid 4. After 1 minute, record the 5. After 1 minute, record the temperature. temperature. Results: 5 degree temperature Result: 7 degree temperature Practical 1 increase decrease ExothermicThis reaction aswas the ______. temperature I knowincreased. this because… ______Practical 2 This reaction was ______. I know this because… Endothermic as the temperature decreased. ______Endothermic reactions

Reaction Start Temp (oC) End Temp (oC) Temp Change (oC) Exo or Endo

A 22.0 33.4

B 18.6 41.7

C 24.3 19.5

D 6.1 21.7

E 22.0 -3.6

F -12.2 2.3

How can you tell this reaction is endothermic? ______This reaction is endothermic because the energy of ______the products is more than the energy than the ______reactants. Energy has been taken in. ______Endothermic or Exothermic? 1. Which type of reaction gives out energy to the surroundings?

2. Thermal decomposition is an example of …

3. is an example of…

4. Which type of reaction causes the temp of the surroundings to decrease?

5. An Ice pack is an example of… use a polystyrene cup better insulator

✓ ✓ ✓

15.8 16.1

21.4 Lesson 3: Investigating endothermic Reactions In and On: Is this reaction endothermic or exothermic? ______Challenge: How do you know?______

Method: 1. Measure out 10 cm3 of water using a measuring cylinder. Record the starting temperature of the water in your results table 2. Collect a polystyrene cup with a pre weighed amount of potassium chloride in it. Record the mass to the appropriate number of decimal places in the table. 3. Add the water to your cup. Record the lowest temperature shown on your thermometer and record this answer to the appropriate number of decimal places. 4. Calculate the change in temperature.

What are the variables for this experiment? Independent______Independent – Mass of potassium chloride (g) Dependant______Dependent – Temperature Control______Control – Volume of water, same polystyrene cup, length of

Masstime of Start temperature End temperature Change in temperature potassium (oC) (oC) (oC) chloride (g)

2 24 22 2

4 24 20 4

6 24 18 6

8 24 16 8

10 24 14 10 Drawing graphs

• Independent variable always goes on the x axis (horizontal) • Dependent variable always goes on the y axis (vertical) • Remove any anomalous results • Ensure you have a title • Ensure you have labelled each axis and state the unit • Ensure gaps are uniform ie. Every square is equal to 2 degrees Celsius • Draw a line of best (either with a ruler or a curve – do NOT join the points)

Conclusion: ______The more marble chips added to the acid, the greater the ______temperature increase. This is an exothermic reaction. ______

Challenge: Why did you use a polystyrene cup rather than a beaker? ______The polystyrene cup provides greater insulation than a beaker. ______How could you improve the experiment to make your results more reliable? ______Carry out the experiment 3 times and take an average of your ______results. Additional notes: ______Lesson 4: Catalysts https://www.youtube.com/watch? v=-4HXaUBbv04 Lesson 4: Catalysts In and On: Which road would you choose and why? Road 2 ______Road 1 ______Road 2 as it is a straighter road ______meaning that you will get to your ______destination quicker. ______Learning Objectives:

• To describe what a catalyst is • Explain how catalysts work What is rate of reaction? Different______reactions go at different speeds. We call the time taken for a reaction______to complete the rate of reaction.

1. What are the 4 factors affecting the rate of reaction?

2. What is the ?

3. What does the rate of a reaction depend on? 1. 2. 4. Why does the rate of reaction increase with increased temperature?

5. Why are catalysts not included in reaction equations?

6. How do catalysts speed up the rate of reaction?

7. Give 2 examples of catalysts

Additional notes: ______Which graph shows a reaction with a catalyst? Explain your answer. ______Graph 2 as there is a lower activation ______energy than in graph 1. ______

______

Using the information sheets (next the show in to page), below the (next fill sheets table the Using information in industry: uses catalysts of Haber Process

Making ammonia from nitrogen and hydrogen.

Nitrogen + Hydrogen → Ammonia

N2 (g) + 3 H2 (g) → 2 NH3 (g)

An iron catalyst is used to speed up the rate of this reaction.

Reactions 2 Catalysts Making Margarine

Vegetable oils are ‘hardened’ using hydrogen gas. This type of reaction is known as hydrogenation.

Example: Ethene + Hydrogen → Ethane

A nickel catalyst is used to speed up the rate of this reaction. Reactions 2 Catalysts Making

A three step reaction. The catalyst is needed in step 2.

Step 1: Sulfur + Oxygen → Sulfur dioxide Step 2: Sulfur Dioxide + Oxygen → Sulfur Trioxide Step 3: Water + Sulfur Trioxide → Sulfuric Acid

A Vanadium Oxide catalyst is used to speed up the rate of this reaction.

Reactions 2 Catalysts Catalytic Converters in Cars They convert harmful emissions into less harmful substances.

Carbon monoxide + Oxygen → Carbon dioxide

2 CO (g) + O2 (g) → 2 CO2 (g)

Carbon monoxide + Nitrogen monoxide → Carbon dioxide + Nitrogen 2 CO (g) + 2 NO (g) → 2CO2 (g) + N2 (g)

Hydrocarbons + Nitrogen monoxide → Carbon dioxide + Nitrogen + Water

Rhodium, Palladium and Platinum can be used as a surface for the catalytic converter.

Reactions 2 Catalysts Oxygen Sulfur trioxide activation

catalyst or increase temperature

increases Lesson 5: Combustion https://www.youtube.com/watch? v=cRnpKjHpFyg Lesson 5: Combustion

In and On: match the reaction to its definition Physical Physical properties of a substance changes but no new reaction substances are made Chemical where energy is taken in reaction Exothermic Chemical reaction where energy is given out reaction Endothermic One or more substances are changed into others by reaction rearranging their atoms Extension: how are hand warmers an example of an exothermic reaction? ______

Learning Objectives: • Summarise combustion using an equation • Make observations during chemical reactions • Write word equations to represent chemical equations

Label the reactants and products for the following reaction:

Methane + Oxygen → Carbon dioxide + Water

Challenge: Write this as a symbol equation:

CH4 + O2 → CO2 + H2O

When a fuel burns, chemical energy is transferred into heat ______. Wood, coal, petrol and gas are all examples of ______. Burning is a ______reaction. The scientific name for burning is ______.

When a fuel burns, it reacts with ______in the air to form carbon dioxide and ______. The reaction also gives out ______energy.

Can you lightYou a candle can onnot the light moon? a Explain candle your onanswer. the ______moon because there is no oxygen gas WhatWhen is the a fuel difference undergoes betweencomplete complete combustion and incomplete, it releases combustion? the maximum amount of energy from the fuel being reacted. Incomplete combustion is ______also a reaction between oxygen and fuel but the products are carbon ______monoxide, water and carbon

Label the reactants and products for the following reaction:

Write this as a symbol equation:

CH4 + O2 → CO2 + H2 O +

Describe why burning is a chemical reaction ______Explain why a fire will burn more brightly is you fan the flames with air ______Describe the problems associated with the production of carbon dioxide ______Challenge Explain why combustion is also known as an oxidation reaction ______

Additional notes: ______• used up in burning accept ‘oxygen burned’ do not accept ‘used up’ • it reacted with fuel or petrol • formed carbon dioxide or carbon monoxide water

It is poisonous or toxic Lesson 8: Explaining changes Lesson 8: Explaining changes

In & On: Mass of water: 250g What would be the mass of the salt solution? Explain your answer. Mass of salt = 5g 255g

Learning Objectives:

• Observe and explain mass changes for chemical and physical processes • Use particle diagrams to explain chemical processes

What is physical change? ______No new products are made, the process is reversible ______e.g. freezing water or melting ice ______TheLaw of conservationLaw of Conservation of mass of Mass ______No______atoms are lost or made during a chemical reaction so the mass______of the products equals the mass of the reactants. ______

Examples: Calcium + Oxygen → Calcium oxide If 6g of calcium reacts with 2g of oxygen, what mass of calcium oxide will form? 8g If 12g of calcium oxide forms from 9g of calcium, what mass of oxygen has reacted? 3g Burning Magnesium

Magnesium and Magnesium Oxide are both solids at room temperature. Oxygen is a gas. Predict – what would appear to happen to mass when they react? ______I predict that the mass will increase as Mg ______bonds with the oxygen in the air.

10.00g 50.00g

54.00.00g

5.00g 9.00g

Describe and Explain what appears to happen to mass when magnesium and oxygen react. ______The______mass increases as Mg bonds with ______oxygen______in the air forming magnesium oxide (white______powder). Challenge: Describe and Explain what appears to happen to mass during the thermal decomposition of copper carbonate. ______Mass appears to decrease. When copper carbonate ______decomposes, carbon dioxide is formed, which is a gas, and ______escapes from the boiling tube, therefore is not accounted for ______when weighing products. ______Total mass of reactants = Total mass of products If one of the reactants is a gas, mass can appear to ______If one of the products is a gas, mass can appear to ______Use the state symbols to predict whether mass would APPEAR to increase or decrease in the reactions. Use full sentences.

CaCO3 (s) → CaO (s) + CO2 (g) ______Decrease as carbon dioxide is a gas and it would escape ______from the container (beaker). ______

4 K (s) + O2 (g) → 2 K2O (s) ______Increase as potassium bonds with oxygen from the air ______to form magnesium oxide. ______Additional notes ______a compound or a new substance has been formed

B

D oxygen carbon dioxide

the same numbers of each type of atom are present Revision The next 2 pages are left blank for you to use for revision in preparation for the end of topic test. Your teacher may ask you to complete a specific revision activity or ask you to revise independently. Suggested activities include: Mind maps, practice questions from the text book, flash cards, memorising key words and concepts. Use this booklet to help you, revision guides and the internet.