PREPARE FOR LABORATORY WORK

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1 Scientific Processes Safety 1. Demonstrate safe practices during field and laboratory investigations Scientific Method 2. Plan and implement investigative procedures including asking questions, formulating testable hypothesis, and selecting equipment and technology 3. Collect data and make measurements with precision 4. Organize, analyze, evaluate, make inferences, and predict trends from data 5. Communicates valid conclusions Critical Thinking & Problem Solving 6. Analyze, review scientific explanations, including hypotheses and theories, as to their strengths and weaknesses using scientific evidence and information 7. Draw inferences based on data related to products and services PREPARE FOR LABORATORY WORK Never perform unauthorized experiments. Know how to use the safety shower, eye wash, fire blanket and first aid kit & bucket of sand. Do not work in the lab without your teacher in the room. DRESS FOR LABORATORY WORK Tie back long hair. Do not wear loose sleeves as they tend to get in the way. Do not wear open shoes on a lab day. Wear lab aprons during all laboratory sessions. Wear safety goggles during all laboratory sessions BUNSEN BURNER SAFETY: A Bunsen burner flame is very hot. The center of the flame will be over 1000 degrees Celsius. Treat burner flames with respect. Always use the main gas shut off valve on the desk to shut off a Bunsen burner. The valve at the base of the burner is only used to control the flame. If your hair or clothing catches on fire stop drop and roll. If someone else's hair or clothing catches on fire, wrap them with a fire blanket to smother the fire. Do not let them run. AVOID HAZARDS Use caution when handling hot glassware. When diluting acid, always add acid slowly to water. Never add water to acid. Keep caps on reagent bottles. Never switch caps. ANIMAL SAFETY Do not cause pain, discomfort, or injury to an animal Wash hands after handling animals SAFETY WITH CHEMICALS AND DISSECTING SPECIMENS: Do not touch or taste any chemical unless specifically instructed to do so. Read chemical labels more than once before using the contents - it is easy to confuse chemicals. When working with chemicals or dissections, keep your hands away from your face. The skin on your face is much more sensitive to irritation than your hands.

2 To smell something, hold it away from your nose and wave your hand over it towards your nose. You may pass out or inhale dangerous gases is you just stick your nose over the container and breathe in. Flush any chemical spill on your skin with plenty of water. The rule of thumb is 15 minutes. When heating anything in a test tube, point the mouth of the test tube towards a wall, away from people. Do not lay the glass stopper from a reagent bottle on the lab table. Hold the handle of the stopper between two fingers while you pour from the bottle. When mixing acids and water, pour the acid into the water. Remember, AnW (root beer) Wash your hands when you are finished with the lab. SAFETY WITH GLASSWARE & BROKEN GLASS Never use chipped or broken glass. If you notice chipped or cracked glassware during a lab please report it to the instructor to be replaced. Broken glass should never be handled with your hands. Use a dustpan and broom to sweep up broken glass. Small pieces can be wiped up using a wet paper towel. Broken glass should be placed in the proper container - either a can for broken glass or a sharps container. Always have the instructor clean up a broken mercury thermometer. Mercury is a poisonous substance and should not be handled. VHHS no longer has any mercury thermometers. Broken glass that has contacted blood must be disposed of in a sharps container. The plastic cylinder guard on a graduated cylinder is to protect the cylinder from breaking if it should tip over. The cylinder guard is not made to slide up and down for measuring. A graduated cylinder should be laid down when it is empty - if it is laying down it can't be tipped over. Remove glass tubing and funnels from stoppers as soon as your lab is finished. If you do not they will become stuck in the stopper. BLOODBOURNE PATHOGEN SAFETY Wear latex gloves anytime you assist someone who is or has been bleeding or vomiting. Clean the entire area (desktop, floor, etc.) with a disinfectant when you are finished caring for the person. Remove your latex gloves by pulling them off inside out. Avoid contact with the outside of the gloves. All paper towels, tissues, latex gloves and other materials used to clean up blood and other possible infectious materials should be disposed of in the proper biohazardous waste bag. Standard Biohazardous waste bags are red with the biohazardous waste symbol on them. If one is not available, use a regular plastic garbage bag and attach a biohazardous waste sticker to the bag. Wash your hands thoroughly with a disinfectant when you are finished.

3 CLEAN UP Consult teacher for proper disposal of chemicals. Wash hands thoroughly, following experiments. IN CASE OF ACCIDENT Report all accidents and spills immediately. Place broken glass in designated containers. Wash all chemicals from your skin immediately with plenty of running water. If chemicals get in your eyes, wash them for at least 15 minutes in an eyewash. The Meniscus When water is placed in a glass or plastic container the surface takes on a curved shape. This curve is known as a meniscus. Volumetric glassware is calibrated such that reading the bottom of the meniscus, when it is viewed at eye level, will give accurate results. Viewing the meniscus at any other angle will give inaccurate results. Erlenmeyer Flasks and Beakers Erlenmeyer flasks and beakers are used for mixing, transporting, and reacting, but not for accurate measurements. The volumes stamped on the sides are approximate and accurate to within about 5%.

4 Graduated Cylinders Graduated cylinders are useful for measuring liquid volumes to within about 1%. They are for general purpose use, but not for quantitative analysis. If greater accuracy is needed, use a pipet or volumetric flask. amount in container amount removed Mass is the amount of matter in an object. There are different kinds of balances used to measure mass. Be sure you understand how your balance works. Some balances give a single reading. Others give two or more readings that you have to add together. For example, look at the triple-beam balance below. Notice that the middle beam measures the largest amounts. To read the mass of an object, find and record the masses shown on each of the beams. Then add the readings. 200g + 70g + 6.5g = 276.5g

5 Scientific Method a systematic procedure for solving problems and exploring natural phenomena 1. Observations (data) are the foundation of the scientific method. This observation might lead to a question regarding the event or characteristic. For example, you might drop a glass of water one day and observe it crashing to the floor near your feet. This observation might lead you to ask a question, "Why did the glass fall?" 2. Hypotheses Hypothesis: In attempting to answer the question, a scientist will form a hypothesis (or some would say a guess) regarding the question's answer. In our example there are many possible hypotheses, but one hypothesis might be that an invisible force (gravity) pulled the glass to the floor. tentative explanations designed to guide experimentation a useful hypothesis must be testable must be rejected or corrected when they conflict with experiment Notice that the hypothesis postulates a relation between the independent and dependent variable, one which produces the change, the other one in which the change is produced. The hypothesis should fit well with what we already believe about the natural order of things.

6 3. Experimentation: Of all the steps in the scientific method, the one that truly separates science from other disciplines is the process of experimentation. In order to prove, or disprove, a hypothesis, a scientist will design an experiment to test the hypothesis. Over the centuries, many experiments have been designed to study the nature of gravity. Let's look at one. In the late 16th century, it was generally believed that heavier objects would fall faster than lighter objects. The Italian scientist Galileo thought differently. Galileo hypothesized that two objects would fall at the same rate regardless of their mass. Legend has it that in 1590, Galileo planned out an experiment. He climbed to the top of the Leaning Tower of Pisa and dropped several large objects from the top of the Leaning Tower. What happens when you drop objects from the top of the tower? The two different objects fall at the same rate (as long as we ignore wind resistance). Data can be qualitative or quantitative. Quantitative data is obtained by making a measurement Qualitative is descriptive data. Accuracy indicates how close a measurement is to the accepted value. For example, we'd expect a balance to read grams if we placed a standard g weight on the balance. If it does not, then the balance is inaccurate. Precision indicates how close together or how repeatable the results are. A precise measuring instrument will give very nearly the same result each time it is used Data is most useful when collected under controlled conditions (experiments) Experiments must be repeatable and reproducible Develop a controlled experiment: Now we will take a closer look at what goes into making a "controlled" experiment. variable - The quantities on which the outcome of an experiment depends are called variables. dependent variable - this will be the single observation, or the result we will be observing. In reality one would observe as many dependent variables as possible. independent variable - this will be the single variable we elect to manipulate. All of the other variables must now be held constant so they don't influence our dependent variable. This way any change that occurs to the dependent variable can be attributed to our independent variable. "control" - this will be the part of our experiment that does not receive the independent variable. This step is critical to the validity of a controlled experiment. trials - Make sure sufficient data is gathered to form a conclusion. (more the better)

7 4. Develop a model or theory or Law = Evaluate Results Galileo's experiment proved his hypothesis correct; the acceleration of a falling object is independent of the object's mass. Why is this true? A few decades after Galileo, Sir Isaac Newton would show that acceleration depends upon both force and mass. While there is greater force acting on a larger object, this force is canceled out by the object's greater mass. Thus two objects will fall (actually they are pulled) to the earth at exactly the same rate. Theories a well-tested explanation for experimental data based on a set of hypotheses. must be discarded or refined when they can't explain new experimental results Natural laws compactly summarize patterns in a large amount of data often apply only under special conditions are descriptions of nature, not explanations Errors. Errors are unavoidable in any experiment. No measurement is perfect. Two kinds of error: random errors uncertainty of measurement, errors in reading a measurement, environmental factors systematic errors-design of experiment, faulty equipment, false assumptions or simplifications Making Science Graphs and Interpreting Data Pie graphs are used to show how a whole is broken up into its parts. Note parts add up to 100%. # of Bald Eagles in 1998 Wisconsin 40% Illinois 2% Iowa 5% Michigan 17% Minnesota 36%

8 Bar graphs are used to compare measurements taken from a number of objects or categories. (demonstrate trend in data) Household Energy Consumption 1979 vs 1997 Quadrillion BTU's Natural Gas Electricity Fuel Oil LP Gas Fuel Type Most scientific graphs are made as line graphs. Line graphs show the relationship between two variables. (In the graph below absorbance and concentration are directly proportional and the concentration of a sample can be determined by measuring the absorbance) The lines on scientific graphs are usually drawn either straight or curved. These "smoothed" lines do not have to touch all the data points, but they should at least get close to most of them. They are called best-fit lines

9 Practice Interpreting Data: 1. Which of the following hypotheses are best represented by this graph? a. Smoking causes cancer. b. Cancer is dangerous. c. One out of a thousand people will get cancer during their lifetime. d. Young people don't get cancer. e. The probability of getting cancer increases with age. 2. Answer these questions about the graph on the below: a. How many total miles did the car travel? b. What was the average speed of the car for the trip? c. Describe the motion of the car between hours 5 and 12? d. What direction is represented by line CD? e. How many miles were traveled in the first two hours of the trip? f. Which line represents the fastest speed? 3. Answer these questions about the graph at to the right: a. What is the dependent variable on this graph? b. Does the price per bushel always increase with demand? c. What is the demand when the price is 5$ per bushel? 4. The bar graph at right represents the declared majors of freshman enrolling at a university. Answer the following questions:

10 a. What is the total freshman enrollment of the college? b. What percent of the students are majoring in physics? c. How many students are majoring in economics? d. How many more students major in poly sci than in psych? 5. Answer these questions about the data table: a. What is the independent variable on this table? b. What is the dependent variable on this table? c. How many elements are represented on the table? d. Which element has the highest ionization energy? e. Describe the shape of the line graph that this data would produce? : a. Atomic Number Ionization Energy (volts)