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. STUDENT NOTES P r e - AP Chemistry U N I T 1 | Page 2 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.