STUDENT NOTES P r e - AP Chemistry U N I T 1 | Page 1

UNIT 1 NOTES: THE LABORATORY

STUDENT OBJECTIVES: Your fascinating teachers would like you amazing learners to be able to…

1. Outline the steps of the scientific method. 2. Form a valid hypothesis. 3. Distinguish between a “law” and a “theory”. 4. Identify the independent, dependent, and controlled variables in an experiment. 5. Distinguish between experimental errors and mistakes. 6. Describe the types of personal safety equipment used in a high school chemistry laboratory. 7. Locate and know how to use the following safety equipment in a high school chemistry laboratory: eyewash, fume hood, safety shower, fire blanket, and fire extinguisher. 8. Outline safe responses for administering first aid. 9. Understand and practice safe laboratory techniques. 10. Define the following terms related to chemical safety: corrosive, toxic, irritant, carcinogenic, flammability, and radioactivity. 11. Describe the purpose of and be able to read an MSDS Sheet. 12. Read a simplified NFPA safety diamond. 13. Identify and be able to state the function of common laboratory equipment. 14. Differentiate between glassware that is “qualitative” and glassware that is “quantitative”. 15. Identify the best piece of equipment to use in certain laboratory settings. 16. Differentiate between qualitative and quantitative data. 17. Define the terms accuracy and precision. 18. Calculate the % error of an experimental value. 19. Identify which pieces of equipment are more precise. 20. Record data according to the appropriate number of significant figures.

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I. WHY LEARN ABOUT CHEMISTRY??? a. Chemistry is ALL AROUND US. Where do we see Chemistry around us?

Environment (Water, Air, Decomposition, Recycling, Water Purification) Food (Digestion, Energy Usage, Cooking, Preservatives) Your Body Medicine Metals Minerals Superconductors Oil/Gasoline Electronics Electricity (Batteries, Power Plants) Products (Textiles, Paper, Paints, Cleaners, Soap) Pesticides Fireworks

b. What kind of careers (besides being a Chemistry teacher!) can Chemistry tie into?

Chefs Pyrotechnicians Analytical Chemist Food Production (Firework technicians) Biotechnologist Specialists Forensic Investigators Food Chemists Nutritionist Petroleum Engineer Geochemist (mining) Doctors Mechanical Engineer Polymer Chemists Pharmacists Environmentalist (plastics) http://portal.acs.org/portal/acs/corg/content?_nfpb=true&_pageLabel=PP_SUPERARTICLE&node_id=11 88&use_sec=false&sec_url_var=region1&__uuid=ed6ed438-6988-40b4-8d7e-5846b1bccfae

II. HOW DO WE APPROACH EXPERIMENTATION IN THE LAB? The answer to this question is something that you may have heard before… the “Scientific Method”. There are many ways to approach a problem, but this is the standard method used in scientific studies.

Question The scientist poses a testable “beginning question” about a system or a process. We will come up with a beginning question every time we do a lab! Observation/Research The scientist makes qualitative and/or quantitative observations. Qualitative: based on _ descriptions _ (ex: color, clarity, texture) Quantitative: based on _ numbers __ (ex: mass, volume, length) Hypothesis The scientist formulates a possible explanation for the observation. A valid hypothesis meets two criteria: 1. It must use conditional language… such as “____ might ______” or “___ may ____” statements. 2. It must be ____ testable ___. STUDENT NOTES P r e - AP Chemistry U N I T 1 | Page 3 Experiment – testing The scientist designs a process or the hypothesis! method that makes appropriate measurements that will either support or reject (refute) the hypothesis. The Scientific Method Based on the results of the is a ___ CYCLE ___! experiment, the scientist either supports & refines their hypothesis or formulates a new hypothesis.

Example 1-1. Indicate whether or not the following hypotheses are valid. If they are not, state the reason. 1. Dr. Leggett has two cats named Tigger and Nala. After observing the cats eating habits she decided to study their food preference and made the following hypothesis: Tigger enjoys his food more than Nala. Not valid – not testable or conditional 2. Mr. Koder was making sure that marvelous truck of his was in tip top shape. He noticed that he typically had to add air in his tires when winter came, but when the weather warmed up, they were just fine. He hypothesized that a decrease in temperature may cause the pressure in his tires to decrease as well. Valid – testable and conditional 3. If leaf color change is related to temperature, then exposing plants to low temperatures will result in changes in leaf color. Not valid – while testable, it is not conditional.

Example 1-2. The example below follows the entire procedure taken by scientists to solve a medical mystery. Answer the questions below based on the scientists’ procedures. The Strange Case of BeriBeri1 - In 1887 a strange nerve disease attacked the people in the Dutch East Indies. The disease was called BeriBeri. Symptoms of the disease included weakness and loss of appetite, and victims often died of heart failure. Scientists thought the disease might be caused by bacteria. They injected chickens with bacteria from the blood of patients with BeriBeri. The injected chickens became sick. However, so did a group of chickens that were not injected with bacteria. One of the scientists, Dr. Eijkman, noticed something. Before the experiment, all the chickens had eaten whole-grain rice, but during the experiment, the chickens were fed polished rice. Dr. Eijkman researched this interesting case. He found that polished rice lacked thiamine, a vitamin necessary for good health. i. State the Problem. What is causing BeriBeri?

ii. What was the original hypothesis? Bacteria may be causing people to get BeriBeri.

iii. How was the hypothesis tested? A group of chickens were tested with bacteria, and a group was tested without bacteria.

iv. Should the original hypothesis be supported or refuted based on the experiment? Refuted – all the chickens got sick.

v. Based on the last research done, what should be the new hypothesis? The lack of thiamine in polished rice may be causing people to contract BeriBeri.

1 http://www.biologycorner.com/worksheets/scientificmethodstories.html STUDENT NOTES P r e - AP Chemistry U N I T 1 | Page 4

III. WHAT’S THE DIFFERENCE BETWEEN A LAW AND A THEORY?

As shown by the scientific method cycle above, scientists will do their experiments over and over again until their results match up with their hypothesis. Even when they do match up, they will repeat the experiment over and over again just to make sure their results are correct, and to refine their findings. Eventually, they will publish their reports in some sort of scientific journal, for other scientists to read. All over the world, other scientific groups will also complete the same experiment, just to verify the findings. Eventually, all of this work can lead to Scientific Laws & Theories!

______Scientific Law ______: This is a concise, factual ___ statement ___ meant to state a proven observation. It is accepted to be true and universal by scientists, and is often expressed in terms of a mathematical equation. Laws are usually developed from a hypothesis that has been tested multiple times.

______Scientific Theory _____: A theory is an ____ explanation ___ of a natural or physical phenomenon based upon proven multiple hypotheses and verified multiple times by independent researchers. Theories will very often include ____ facts and laws ______in order to prove their point. Some scientific theories include the theory of evolution, the theory of relativity, the atomic theory, and the quantum theory. All of these theories are well documented and proven without a reasonable doubt – yet scientists continue to tinker with the component hypotheses of each theory in order to make them more elegant and concise as new technology is developed. Theories can be tweaked, but they are seldom, if ever, entirely replaced.

The biggest difference between a law and a theory is that a theory is much more complex and dynamic. A law governs a single action, where a theory explains an entire group of related phenomena.

For example, Charles’s Law says that “as temperature of a gas increases, the volume of that gas increases”.

There is even a mathematical formula that goes along with this relationship, V1/T1 = V2/T2.

However, there is a theory called the “Kinetic-Molecular Theory of Gases”. The theory goes into explaining why gases behave the way they do, and why they show particular properties. There are a lot of different points to the theory, but there is no simple statement, and no set formula. A lot of laws (including Charles’s Law) can be used to prove the Kinetic-Molecular Theory of Gases.

IV. WHAT KIND OF VARIABLES ARE THERE IN EXPERIMENTATION? Most experiments have _____ variables ______– quantities that may or may not be changed during the experiment. There are three types of variables in an experiment and you will need to be able to identify them and state them in your lab reports.

Independent This is the variable that the scientist is changing to see the effect on the dependent variable. He or she Variable is ____ independently ______varying this value. This is the variable that you, the scientist changes.

This is the variable that is ____ measured ______in response to a change in the independent Dependent variable. The changes in the independent variable that were made by the scientist _____ cause ____ Variable or _____ result in ______a change in the dependent variable. These are the “results” which you, the scientist, measures and records.

Other factors may alter the dependent variable. The scientist wants to determine the effect of ONLY Control the chosen independent variable on the dependent variable, so all other factors are kept Variable(s) _____ constant ______. Control variables are frequently referred to as constants. NOTE: this is a different concept than a control group which is used as comparison.

DRY MIX: dependent variable is resulting on the y axis, manipulating is the independent variable on the x axis when graphing! STUDENT NOTES P r e - AP Chemistry U N I T 1 | Page 5

Tired of finding dirt on your floor after you’ve just vacuumed it? Then it’s time for you to try the…. Suck-O-Matic 5000 Bagged Vacuum Cleaner

Guaranteed to pick up 20% more dirt than other leading bagged vacuum brands!

Available for $159.99 at your nearest vacuum retailer!

Example 1-3. Answer the following questions about the above advertisement: i. How could you test the claim made by the advertisement above? Have several different brands of bagged vacuums and run them over an amount of dirt. Make mass measurements of the dirt initially and after vacuum has passed over it.

ii. What would be your beginning question for this experiment? Which vacuum will pick up the most dirt? -or- Will the Suck-O-Matic pick up more dirt than other brands? iii. What would be your independent variable in this experiment? Brands of vacuums iv. What would be your dependent variable in this experiment? Amount of dirt picked up v. What would be some control variables in this experiment? Only use bagged vacuum cleaners, use the same amount and type of initial dirt, vacuum over the dirt for the same amount of time, make sure all vacuums have empty bags initially

V. WHAT IS THE DIFFERENCE BETWEEN MISTAKES AND SOURCES OF ERROR? Not always will things go according to plan in a lab. There are two types of reasons why a lab might not be perfect… 1. ______Human Mistake ______- this is a screw-up caused by someone in the lab. The procedure was not followed, or something was done incorrectly. They cause you to have to redo the lab.

2. ______Source of Error ______- this is a limitation of a procedure. This is very different than a mistake! These cause you to redesign the lab. A source of error should be seen as an opportunity to improve an experiment to get better results the next time. We will be identifying sources of error for labs that we do in class. Some questions to ask yourself to determine sources of error: a. Could the procedure be done more precisely? (Think measurements.) b. Could the procedure be done with less _____ contamination ______? c. Were the variables to be held constant REALLY held constant? d. What ____ assumptions ______were made in the collecting of data? e. Was there a level of subjectivity in interpreting the data?

Example 1-4. For the vacuum lab you designed above, what could be some sources of error for the experiment? Assumed all carpet was the same height, assumed all pieces of dirt were the same size STUDENT NOTES P r e - AP Chemistry U N I T 1 | Page 6

Example 1-5. For each of the following, determine if it is an example of “human mistake” or “source of error”. If it is a “source of error”, then state a way to improve the experiment. i. The student miscalculated the density of the material. Human mistake.

ii. The temperature of the room was assumed to be constant throughout the experiment. Source of error. The temperature of the room may have varied, affecting the results. The experiment could be done more precisely in a temperature-controlled room. iii. When transferring the powder from the weighing paper to the flask, a small amount of powder remained on the weighing paper. Source of error. Not all of the measured volume was transferred. The experiment could be done using more precise tools. iv. The student used too much NaCl and had to repeat the experiment. Human mistake.

v. The student added the solutions in the wrong order. Human mistake.

vi. The student compared the results to his hand-drawn graph and estimated the volume to be about 145 mL. Source of error. A better estimate could be made using a more precise graph or correlation.

vii. Twenty drops of each solution were added to the reaction. Each drop was assumed to be the same volume. Source of error. The experiment could be done using more precise measurements

VI. HOW CAN I KEEP SAFE IN THE LAB? (PERSONAL PROTECTION EQUIPMENT) a. Wear ___ goggles _____ at all times when you are in the laboratory area. Goggles must fit securely around the eye, or you are at risk of getting chemicals or broken glass in your eye! WE WILL TAKE POINTS OFF YOUR LAB IF YOU ARE NOT WEARING GOGGLES AT YOUR LAB STATION. b. Wear ___ closed-toe ______shoes to all labs due to broken glass or spilled chemicals on the floor. YOU WILL NOT BE ALLOWED TO PARTICIPATE IN LABS IF YOU ARE NOT WEARING THE RIGHT SHOES! c. Wear an ___ apron ______during all labs. Some of the chemicals we use may not be harmful, but they could stain your clothes! d. Eating & drinking are not allowed during labs. e. ______wash your hands ______with soap before leaving the lab. Just imagine if you have chemicals left on your hands and you… eat a bag of potato chips… rub your eyes… you get the idea! f. Pull back _____ long hair ______into a ponytail, especially on days where we use the Bunsen burners.

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VII. WHAT ARE SOME IMPORTANT SAFETY TIPS FOR THE LAB? I should have used a. Never _____ taste ______anything in the lab! YUCK! the fume hood! b. Do NOT perform any unauthorized __ experiments ____ in the lab, no matter how harmless you think they are. c. Use the ____ fume hood ______for any reaction that may produce a harmful (toxic) gas. d. Never put extra chemicals back into the ___ bottle _____. If you pour too much out of a bottle, simply ask your teacher for the best way to dispose it. If you put it back into the original bottle, you may ____ contaminate _____ the rest of the chemical! e. Make sure you ___ close ______any chemical containers after use. Some chemicals can dry out, absorb water from the atmosphere, or react with water from the atmosphere. f. Make sure to clean off any spilled chemicals from the ____ balances _____. They can react and corrode the metal of the balance. g. Always ______ask the teacher ______for the best way to dispose of wastes at the end of the lab. Quite frequently, there will be a special waste container for chemicals left over after a lab. NEVER throw ____ solids ______in the sink, as it may clog them up! h. Smell chemicals through ____ wafting ______the vapors toward your nose. Use your hand to wave the vapors toward you so that you can smell them. i. Point heated test tubes ____ away _____ from people. They may erupt like a geyser and splash the contents on you! j. Always pour ___ acid ____ into ___ water _____, and never the opposite. If you do it the wrong way, it can create too much heat and break the glass! (HINT: A&W Root Beer – A[cid] in W[ater]) k. Know where all the safety equipment is in the room, such as: exits, fume hood, fire blanket, fire extinguisher, emergency shut-off, safety shower, eyewash station, first-aid kit, and glass disposal box. l. USE YOUR ______common sense ______! Most laboratory accidents can be prevented this way. VIII. WHAT SHOULD I DO IF AN EMERGENCY HAPPENS? a. TELL THE ____ teacher _____. This should always be your first response to any emergency situation. b. Spills on the countertop/floor: i. Acid Spills – Place ______baking soda ______on the spill to neutralize the acid before you attempt to wipe it up. ii. Base Spills – Place _____ vinegar ______on the spill to neutralize the base before you attempt to wipe it up. c. Chemicals in your eye: i. Eyewash station – you must remain in the eyewash station for at least ___10-15____ minutes in order to flush all the chemical out of your eyes. However, we should never have to use this… if we are wearing our goggles! d. Chemicals on you (Chemical Burns): i. Do not try and neutralize an acid or base chemical on you! The process creates lots of heat which can burn you.

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ii. If it is a small drop, rinse the area thoroughly with water at the sink. iii. If you get a large amount of chemical on you, then you must go and use the ____ safety shower ______. e. Fire: i. For very small fires, an ______inverted beaker ______is very effective. ii. If someone’s clothes are on fire, use the _____ fire______blanket ______. Simply wrap the blanket around the person. iii. For larger fires, the ______fire extinguisher ______is necessary. The three steps to using the fire extinguisher are: 1. ___ pull ____ the silver pin which will break the seal 2. ___ point ___ the nozzle at the base of the fire 3. ___ press ___ the two handles together iv. Do not put ____ water _____ on fires in the chemical laboratory! For chemical fires, water can sometimes make the fire worse! v. Also, it is a good idea to go and press the Emergency Shut-Off button. This will turn off the gas coming out of the valves. f. Thermal (Heat) Burns: i. Flush the area with cold water. g. Other Random First-Aid Tips: i. For ______fainting ______, provide the person with fresh air, if possible. Have the person recline so that the head is lower than the rest of the body. ii. For ______major cuts (wounds )______, apply pressure to the wound and get medical attention quickly. iii. For _____ poisoning ______, call Poison Control.

I am not your maid! Clean up your equipment, lab station, and sink!!!

IX. UNDERSTANDING SAFETY VOCABULARY

a. All chemicals have safety warnings listed on the outside of the container and on their MSDS sheet (which we will talk about later). It is important to understand these safety warnings in order to keep yourself protected.

i. Corrosive: ______eat away at objects, attacks & burns skin ______ii. Toxic: ______poisonous ______iii. Irritant: ______causes a rash or allergic reaction ______iv. Carcinogenic: ______can cause cancer ______v. Flammability: ______easily set on fire; combustible ______vi. Radioactivity: __spontaneously emits radiation resulting from changes in the nuclei of atoms __ STUDENT NOTES P r e - AP Chemistry U N I T 1 | Page 9

b. Chemical containers and MSDS sheets also display the NFPA (National Fire Protection Association) Hazard Diamond. The hazard diamonds are placed on the containers for easy and quick identification of basic hazards associated with each chemical.

FLAMMABILITY Numbers are used in the squares HAZARD to indicate the amount of danger

for each of the specified hazards: (red)

HEALTH REACTIVITY 0 ______no hazard____ HAZARD HAZARD 1 ______slight______(blue) (yellow) 2 ______hazard______SPECIAL

INFORMATION 3 ______extreme____

(white) 4 ______deadly______

Example 1-6. The NFPA diamond for highly concentrated HCl (Hydrochloric Acid) is below. Determine the meaning for each of the ratings.

No flammability hazard 0 Extreme health hazard Reactivity hazard 3 2

c. Material Safety Data Sheets (MSDS) are bulletins developed to communicate the potential hazards to users. It also includes information such as basic physical and chemical properties, storage instructions, first aid measures, and disposal procedures.

Example 1-7. On the next page, you will find the first page of a MSDS for highly concentrated Hydrochloric Acid. We commonly use this chemical in lab, but at much lower concentration levels. Answer the following questions using the MSDS sheet:

i. Do we need to be concerned with flammability for this substance? No – NFPA diamond rating for flammability is zero

ii. How should we store this substance? Store in a dedicated acid cabinet away from water

iii. What are some health hazards we should be concerned of with this substance? Severely corrosive to body tissues, especially skin & eyes – avoid all body contact

iv. What should we do if someone accidentally swallows this substance? Drink 1-2 cups of water or milk, followed by gastric antacid; call physician or poison control STUDENT NOTES P r e - AP Chemistry U N I T 1 | Page 10

STUDENT NOTES P r e - AP Chemistry U N I T 1 | Page 11 X. LABORATORY GLASSWARE (pictures not to scale)

QUALITATIVE OR EQUIPMENT NAME FUNCTION? QUANTITATIVE?

Qualitative Large mouth glass containers used to contain approximate volumes of Beaker (holding vessel) liquid Long tube with a stopcock that opens and closes; it is used to precisely deliver solutions, especially in a titration Quantitative Buret ALSO: BE AWARE OF THAT THEY COUNT BACKWARDS, as they measure how much liquid has been delivered! Small mouth glass container used to contain approximate volumes of Qualitative liquid; the small mouth accommodates a stopper for storage or to Erlenmeyer Flask (holding vessel) prevent spillage while mixing

Graduated Cylinder Quantiative Used to measure and deliver precise volumes of liquids

Graduated Pipet Quantitative Used to deliver precise volumes of liquids

Qualitative Glass cylinder that holds liquids being tested in an experiment; does not Test Tube (holding vessel) have any measurement markings on it

Used to precisely contain a specific volume; commonly used when Quantitative Volumetric Flask making aqueous solutions (aqueous = water + dissolved compound) STUDENT NOTES P r e - AP Chemistry U N I T 1 | Page 12 XI. OTHER LABORATORY EQUIPMENT (pictures not to scale)

EQUIPMENT NAME FUNCTION?

Beaker Tongs Circular tongs with rubber coating that can wrap around and hold a hot beaker

Bunsen Burner Gas flame burner that uses methane as a fuel source

Clay Triangle Set on a ring clamp, it is used to support a crucible or a funnel Ceramic bowl with a lid that is used to heat small amounts of solid substances to high Crucible temperatures Crucible tongs Used to pick up and hold small items, such as crucibles Double Buret Attaches to ring stand to hold two burets Clamp Used to contain small volumes of solutions in order to heat the mixture and evaporate the Evaporating Dish solvent Silicon hot pads that can withstand high temperatures and are used to hold/transfer hot Hot Hands containers Ring Clamp Ring-shaped clamp that attaches to the ring stand to support equipment STUDENT NOTES P r e - AP Chemistry U N I T 1 | Page 13

EQUIPMENT NAME FUNCTION?

Ring Stand Long metal pole on a base; along with clamps, it is used as a support of equipment set-ups

Scoopula A folded piece of metal that is used to transfer solids A plastic or porcelain plate with wells used to test reactions during micro labs; sometimes called Spot Plate a “well plate” Has a flint that sparks to initiate flame on Bunsen burners; DO NOT PLAY WITH THESE AND Striker WEAR OUT THE FLINT! Test tube clamp Clamps a test tube or other equipment onto a ring stand

Test tube holder Spring metal holder used to hold or transfer hot test tubes

Transfer Pipet Plastic, qualitative pipet that is used to dispense chemicals; often used in place of a dropper

Watch Glass Concave glass dish used to hold chemicals or as a cover for evaporating dishes and beakers

Wire Gauze Used to help support equipment and spread the heat of a burner flame

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XII. MEASUREMENT AND OBSERVATIONS a. As a reminder, there are two basic types of data collected in the lab:

______Quantitative ______: numerical information (ex: the mass of the salt was 3.45 g)

______Qualitative ______: non-numerical, descriptive data (ex: the color of the solution is magenta)

b. When dealing with quantitative data, there can be either errors or uncertainty in your results. The terms scientists typically use are accuracy and precision – they are not the same!

1. ____ Accuracy ______refers to the degree of closeness of measurements to the __ actual ___ (true) value. The true value is sometimes also referred to as the accepted or theoretical value. The true value is often a value reported on a reference chart.

Accuracy is most commonly reported by using % error:

true experimental %error  100  true 

The experimental value is what you would have gotten as your measurement in the experiment. Percent error can come out to be either positive or negative.

Example 1-8. A student weighs a beaker and records its mass as 47.21 g. The actual mass of the beaker is 47.93 g. What was the student’s % error?

1.5%

Example 1-9. Billy Fumblefinger’s lab group had 22.5% error in their lab. They found the mass of the object to be 122.4 grams. What was the actual mass of the object, as written on the board by their teacher?

157.9 g

2. _____ Precision _____, also called _____ reproducibility _____, is the degree to which repeated measurements under changed conditions show the same results.

While you can repeat the same results over and over again and show precision, those results may or may not be accurate. Take into consideration the following dart boards:

accurate, not precise not accurate or precise accurate and precise precise, not accurate STUDENT NOTES P r e - AP Chemistry U N I T 1 | Page 15

c. The term precision can also be used for glassware. The ___ closer _____ the range of markings of a piece of glassware, the more precise that piece of equipment is.

Example 1-10. Which of the following pieces of glassware is the most precise? Which is the least precise?

d. Because different pieces of equipment have different levels of precision, we cannot report quantitative results the same every time. We must use the concept of ______significant figures ______to determine how many digits are appropriate to report.

When making a measurement in the lab, we always report all ___ certain ___ digits plus __ one ____ uncertain digit. The uncertain digit will require you to estimate between the lines. If you estimate a measurement to be on a line, you must add a ___ zero ____ to show that you are estimating the uncertain digit to be exactly on the line.

Not reporting measurements to the correct amount of significant figures (AND WITH __ UNITS ___!) can cause you to lose points on labs, quizzes, and tests!

Also – be aware that with glassware, you will have a curvature of the liquid – referred to as a ____ meniscus ______. Always make your measurements from the bottom of the meniscus.

Example 1-11. Read the following ruler & glassware to the correct number of significant figures.

Notice how the buret counts backwards, as it is showing how much liquid has been delivered to another

container!

How much liquid has been delivered from this buret?

Graduated Cylinder Buret