How To Complete and Experiment and Write a Lab Report: Using Questions to Write a Hypothesis With Clear Independent and Dependent Variables

Transcription

1 How To Complete and Experiment and Write a Lab Report: Using Questions to Write a Hypothesis With Clear Independent and Dependent Variables 1

2 I can How to Write a Hypothesis What is a hypothesis? A hypothesis is a tentative statement that proposes a possible explanation to some phenomenon or event. A useful hypothesis is a testable, measurable statement, which may include a prediction. In writing a hypothesis a tentative relationship is stated. If you always ask yourself if one thing is related to another, then you should be able to test it. How are hypothesis written? 3 Different Methods 1. RELATIONSHIP METHOD-"IF THE INDEPENDENT VARIABLE IS RELATED TO DEPENDENT VARIABLE, THEN THE DEPENDENT VARIABLE WILL DO THIS (PREDICTION THAT ANSWERS THE QUESTION) BECAUSE..." Look at the two examples of hypotheses below: Question/Purpose: To study how the mass of a car effect the distance it will travel down a ramp. "If the mass of a car is related to the distance the car will travel down a ramp, then the heavier the car the farther the car will travel because it has more momentum." Question/Purpose: How does the color of a shirt effect the heat it absorbs? "If the color of a shirt is related to the heat it absorbs under a heat lamp, then the darker the shirt the hotter it will be because dark colors do not reflect light waves." 2. TRADITIONAL METHOD-"IF THE INDEPENDENT VARIABLE (WHAT IS CHANGED), THEN THE DEPENDENT VARIABLE WILL DO THIS (PREDICTION THAT ANSWERS THE QUESTION) BECAUSE..." Look at the two examples of hypotheses below: Question/Purpose: How does the mass of a car effect the distance it will travel down a ramp? "If a heavier car is run down a ramp then the heavier the car will travel farther than a lighter car because it has more momentum." Question/Purpose: To study how the color of shirt effect heat absorption. "If a black shirt is placed under a heat lamp, then the black shirt will be hotter than a lighter colored shirt because dark colors do not reflect light waves. 2

3 Notice that all three of these ways are statements that contain the words if, then, and because. These words are necessary in a formalized hypothesis. The if tells what is being changed, the then tells the prediction of what will happen, and the because tells why the scientist thinks this will happen. Two Variables in a Hypothesis Formalized hypotheses contain two variables. One is independent and the other is dependent. The independent variable is the one you, the scientist change, manipulate, or compare. This is represented in the upper left hand column of a data table and as the label on the x-axis in a graph. The independent variable is the I change variable; as the scientist, it s the thing that I m changing or messing with (or manipulating) in the experiment! The dependent variable is the one that you measure; it s the data and results that you intend to collect (distance the car went). This variable is represented in the upper right hand column of a data table and as the label on the y-axis in a graph. The dependent (responding) variable depends on how you manipulate the independent variable. This is found in the Then part of the hypothesis. The because statement explains why the scientist thinks the prediction given in the then statement will happen. Why Write a Hypothesis The ultimate value of a formalized hypothesis is it forces us to think about what results we should look for in an experiment. Of course, the strongest hypotheses also include a measurable prediction. More on THAT in just a minute! Measurable Hypotheses A strong scientific hypothesis not only uses one of the two formalized methods shown above, but it should also include a measurable prediction about the results. Basically, this means that when you write a hypothesis, you want to indicate what is being measured. Let s look at some examples. The prediction is underlined. Question/Purpose: How does the mass of a car effect the distance it will travel down a ramp? If the mass of a car is related to the distance the car will travel down a ramp, then the heavier the car the farther the car will travel because of has more momentum. Question/Purpose: How does the color of a shirt effect the heat it absorbs? If a black shirt is used, then the darker the shirt will be hotter than a lighter colored shirt because dark colors do not reflect light waves. To make your prediction measurable, you are basically using words that indicate measurement (i.e. travel farther, temperature). These words indicate that there are numbers that need to be recorded (whether it is distance a car traveled or the temperature recorded). That is the ultimate goal of any science experiment, to generate data. With data, a student can begin to find answers to questions and solutions to problems. 3

4 Dissecting the Hypothesis Fill in the chart below showing how each part of the hypothesis is different If Then Because variable The variable that is variable or variable The variable that is why the scientist thinks the prediction given in the statement will happen. Read the introduction, example and then complete the Practice Writing hypothesis problems 1-5 below: Hypothesis Practice Answer the following questions by creating a hypothesis. 1. What effect does the size of a rubber ball have on the height it bounces? If then because 2. What effect does fertilizer have on tomatoes? If then because 3. What effect does the amount of wings have on the height a rocket flies? If then because 4

5 4. What effect does playing video games have on blood pressure? If then because 5. What effect does the size of a coin have on how many water drops it can hold? If then because 5

6 More Hypothesis Practice Alka-Seltzer Video Observation What happens when an Alka-Seltzer is added to water? A student is interested in designing several experiments to test the factors that effect how quickly an Alka-Seltzer tablet dissolves in water (solution rate). For each question, write a hypothesis that could be tested with an experiment. Be sure each hypothesis is in the proper If then because format. See example below. Example: Question/Purpose: What effect does stirring have on solution rate of a tablet? Hypothesis: If the stirring of water is related to solution rate, then the tablet will dissolve faster in water that is stirred because when sugar is added to water, it dissolves when it is stirred. Hypothesis: If a tablet is placed in water that is stirred then the tablet that is stirred will dissolve faster than a tablet that is not stirred because when sugar is added to water, it dissolves when it is stirred. 1. Question/Purpose: What effect does the water temperature have on how fast a tablet will dissolve? Hypothesis: 2. Question/Purpose: What effect does crushing the tablet have on how fast it dissolves? Hypothesis: 3. Question/Purpose: What effect does adding soda to the water have on how fast the tablet dissolves? Hypothesis: 6

7 I can Lab-Testing a Hypothesis Bombs Away Question: What effect does the height of a water dropper is held at have on the size of a spot the water drop will make? Hypothesis: Materials: 1-50ml Beaker 1- Eyedropper 1- Meter Stick 2- Pieces of Construction Paper Procedure: 1. Fill your beaker with water. 2. Place your meter stick with the 0 cm end on the construction paper. 3. Release one drop of water from 10 cm onto the paper. Be sure the tip of the eyedropper is even with each of these centimeter marks. Do not hold the dropper too close to the meter stick or the drop will hit the end of the meter stick. 4. Draw around each wet spot between drops and label the spot with the distance the drop fell and the trial number. Measure the diameter of the drop in millimeters and record it in the data table. Make qualitative observations describing what the drop did in the qualitative observation section. 5. Repeat steps 3 and 4, 2 more times. Each time move the meter stick after each drop so the next drop lands on a different area of the paper. 6. Take a new sheet of construction paper. Place your meter stick with 0 cm end on the construction paper. 7. Release one drop of water from 50 cm onto the paper. Be sure the tip of the eyedropper is even with each of these centimeter marks. Do not hold the dropper too close to the meter stick or the drop will hit the end of the meter stick. 7

8 8. Draw around each wet spot between drops and label the spot with the distance the drop fell and the trial number. Measure the diameter of the drop in millimeters and record it in the data table. Make qualitative observations describing what the drop did in the qualitative observation section. 9. Repeat steps 7 and 8, 2 more times. Each time move the meter stick after each drop so the next drop lands on a different area of the paper. Qualitative Observations: Height-10 cm Trial 1: Trial 2: Trial 3: Height-50 cm Trial 1: Trial 2: Trial 3: Drawing: Draw the set up of the two different tests below: 10 cm Height 50 cm Height 8

9 Quantitative Observations: Data Table 1: Height of a Water Dropper and Average Size of a Spot Height of a Water Dropper 10 cm height Trial 1 Trial 2 Trial 3 Average Size of a Spot 50 cm height Reflection Questions: 1. What was the independent variable in this lab? 2. What was the dependent variable in this lab? 3. Explain how the height in which the dropper was held affected the size the drop made. 4. Did your hypothesis work? Give evidence to support your answer. 9

10 I can (Title of Lab Report) Fill in the parts of graphic organizer below, based upon the lab, using complete sentences. Section A-Question/Purpose, Hypothesis, Materials, Variables Question/Purpose: Hypothesis (If/then/because statement): Independent Variable (what variable is being changed also the top left hand column of the data table): Dependent Variable (what will happen also the top right hand column of the data table): Materials (bullet point list with how many of each was used): 10

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12 I can Qualitative and Quantitative Observations Observations are an important part of scientific experiments. Hypotheses are accepted or rejected based on how well they explain observations. Some observations, such as "the plant turned brown" are qualitative; these observations have no associated numbers. A quantitative observation includes numbers, and is also called a measurement. A measurement is obtained by comparing an object to some standard. Any observation is useful to a scientist, but quantitative observations are commonly considered more useful. Even if the measurement is an estimate, scientists usually make both qualitative and quantitative observations in every experiment. Qualitative Observations Example from the Bombs Away Lab Qualitative Observations: Height-10 cm Trial 1: Trial 2: Trial 3: Height-50 cm Trial 1: Trial 2: Trial 3: Drawing-Draw the set up of the two different tests below: 10 cm Height 50 cm Height 12

13 I can Quantitative Observations-How to Create a Data Table and Graph It all starts with the question for the lab. Every lab begins with a question. In that question there is an independent and dependent variable. In a data table, the independent and dependent variable of that question is analyzed. How? A data table is a series of rows and columns that contains the results (dependent variable) of what is being tested (the independent variable). Therefore, the question of the lab helps set up the data table. For example, in the Bombs Away lab that was just performed the question of that lab was as follows: Independent Variable Dependent Variable Question: What effect does the height of a water dropper is held at have on the size of a spot the water drop will make? Notice how the independent and dependent variable identified in the question is used to set up the data table for this lab, including the title! Independent variable from the question of the lab Dependent variable from the question of the lab Data Table 1: Height of a Water Dropper and Average Size of a Spot Height of a water dropper Trial 1 Trial 2 Trial 3 Average Size of a Spot 10 cm height 50 cm height The importance of the independent and dependent variable in a lab does not stop with the data table. The information in the data table is used then to create the graph for the lab. In a graph, the final results are graphed. Therefore, if three trials are done, it is the average measurement that is recorded. Graph 1: Height of a Water Dropper and Average Size of a Spot Average Size of a Spot (mm) Dependent Variable 10 cm height 50 cm height 13 Height of a Water Dropper

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16 I can How to Calculate Average Foldable-Data Table/Graphing 16

17 Practice-Data Table and Graphing Using the example lab questions below fill in the missing information in the data table and graph each data table. Use a single underline to identify the independent variable and use a double underline to indicate the dependent variable in each question. Practice #1 Question-What effect does the size of a parachute have on the time a parachute stays in the air? Data Table 1: Size of a Parachute and Average Time a Parachute Stays in the Air Trial 1 Trial 2 Trial 3 10 meters in diameter 5.25 min. 6.0 min min. 30 meters in diameter 10.0 min min min Graph 1: 17

18 Practice #2 Question-What effect does the weight of a car have on the speed it travels down a ramp? Data Table 1: Trial 1 Trial 2 Trial 3 15 gram car 14 sec. 16 sec. 18 sec. 55 gram car 5 sec. 8 sec. 6 sec. Graph 1: 18

19 I can Lab-Testing a Hypothesis and Making Qualitative and Quantitative Observations Drops on a Penny Lab Background:. Water contains unique physical features. A special property of water is surface tension. The surface of the liquid behaves as an elastic membrane in which surface tension appears, allowing the formation of drops and bubbles. When water is dropped on a penny, the surface tension allows the water to form a bubble dome on the penny. Question/Purpose: What effect does the side of a penny have on the number of drops it can hold? Hypothesis (Claim): Materials: 1 penny 1 beaker with water 1 medicine dropper 1 Paper towel 1 magnifying glass Procedure: 1. Fill a beaker with water. Take a penny and place it in front of you. 2. Take the medicine drop and fill it up with water from the beaker. 3. Carefully drop water on the penny. Keep count of how many drops of water the penny holds. Record how many drops the penny held. 4. Dry the penny and repeat step 2 two more times. Record your findings in the data table. 5. Dry the penny and flip it over completing steps Average your three trials for a more accurate idea of how many drops of water a penny will hold. Qualitative Data: Look at each side of a penny with a magnifying glass. Draw each side in the boxes below. Heads Side Tails Side 19

20 Describe what happened as water was dropped on each side of the penny. Heads Side: Tails Side: Quantitative Data: Data Table 1: Trial 1 Trial 2 Trial 3 20

21 I can (Title of Lab Report) Fill in the parts of graphic organizer below, based upon the lab, using complete sentences. Section A-Question/Purpose, Hypothesis, Materials, Variables Independent Variable (what variable is being changed also the top left hand column of the data table): Dependent Variable (what will happen also the top right hand column of the data table): 21

22 Section B-Procedure 22

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24 Section C-Qualitative and Quantitative Data 24

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27 I can Writing Analysis Once the data table and graph have been done, the data is then analyzed. The purpose of this is to explain the results of the data as recorded in the data table and graph. The goal of this is to show the relationship between the independent and dependent variable. Fill in the data table below with the results from the Drops on a Penny Lab. Then write analysis for the results following the instructions given in the graphic organizer below the data table. Data Table 1: Section D-Analysis 27

28 I can Identifying the Experimental Error and Writing the Conclusion Scientists often make many measurements during experiments. As in just about every human endeavor, errors are unavoidable. In a scientific experiment, this is called experimental error. Systematic errors are part of the experimental setup, so that the numbers are always skewed in one direction. For example, a scale may always measure one-half of an ounce high. Random errors occur because a measurement is not made precisely. For example, a stopwatch may be stopped too soon or too late. To correct for this, many measurements are taken and then averaged. Experiments always have a margin of error associated with them. In an experiment, if a result is inconsistent with the results from other samples and many tests have been done, it is likely that a mistake was made in that experiment. The inconsistent data point can be thrown out. Let s Practice Identifying Source Error Observe the following experiments performed by the teacher and record the experimental errors. In the box to the right explain why it is a source error. Below identify how the lab could be improved (another way of saying what can be done to eliminate the source error next time). Ball Bounce Question: Can a smaller ball bounce higher than a basketball? Source Error Why? 28

29 Rubber Band Question: Which type of rubber band flies the longest distance? Source Error Why? Mass and Speed Question: How does the mass affect the speed of a car? Source Error Why? 29

30 Write out the conclusion using the Drops on a Penny Lab. Follow the instructions in each box on the conclusion graphic organizer. Section E-Conclusion 30

31 I can Come Fly with Me Lab Background: There are three forces that act upon a paper airplane. Those forces are lift, weight, and drag. Drag is the aerodynamic force that opposes an aircrafts motion through the air. Lift is the force that holds an aircraft in the air. Lift is caused by wind going over and under the wings. Finally, weight is a force caused by the gravitational attraction of the Earth. In this lab, we want to find out what effect does the weight of an airplane have on its flight? In other words, does the weight of an airplane affect how far a paper airplane can travel? Problem/Question: Does the weight of a paper airplane affect how far it flies? Hypothesis: Materials: 1-Sheet of 8.5 x 11 paper 1-Metric measuring tape 1-Paper Clip Procedures: 1. Build a basic airplane 31

32 2. Take the basic airplane, standing behind the starting line, gently fly the plane. 3. When the plane lands, measure the distance with the measuring tape and record that number in the data table. 4. Repeat two more times and record the data in the data table. Then calculate the average distance flown. 5. Take the basic airplane and add a paper clip in the middle along the bottom of the plane. 6. Repeat steps 1-4. Qualitative Observations: (How did the plane fly for each trial? Be sure to be specific!) Drawing: 32

33 Quantitative Data: Data Table 1: Trial 1 Trial 2 Trial 3 Lab Report: On the next several pages is the format for lab reports will be written in junior high. Using the Paper Airplane Lab, which was done in this note packet, we will write a lab report together. Be sure to keep this note packet and all its contents in the Lab Report Section of your science binder. This will be a resource for you throughout this year 33

34 (Title of Lab Report) Fill in the parts of graphic organizer below, based upon the lab, using complete sentences. Section A-Question/Purpose, Hypothesis, Materials, Variables Independent Variable (what variable is being changed also the top left hand column of the data table): Dependent Variable (what will happen also the top right hand column of the data table): 34

35 Section B-Procedure 35

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37 Section C-Qualitative and Quantitative Data 37

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39 Section D-Analysis Section E-Conclusion 39

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