analyzing data and making conclusions identifying possible sources of error

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1 Lesson 3 Scientific Inquiry independent variable dependent variable hypothesis fair test controlled variable observations source of error conclusion testable question variable Vocabulary (0 Grade 8 Science In the last two lessons you investigated and compared the viscosity of different fluids. You also found out that there are some factors that can affect the viscosity of a particular fluid at a given time. For example, pressure can cause a fluid to be more or less viscous. Have you ever wondered why milkshake straws have a larger diameter? If you've tried to drink a milkshake through a straw with a smaller diameter, you would have found you have to work harder and apply more pressure to get the milkshake to flow through the straw as quickly as it would with a larger straw. This next section will lead you through a science inquiry to investigate another factor that affects flow rate. Factors that Affect Flow Rate Learning Outcomes After completing this lesson you will be able to use the scientific inquiry process to conduct a fair test to determine factors that affect flow within a given system. The process includes identifying variables creating a hypothesis planning and conducting an experiment making and recording observations analyzing data and making conclusions identifying possible sources of error reflecting on the process and identifying possible implications for daily life Module 1, Lesson 3 23

2 24 Module 1, Lesson 3 Grade 8 Science Step One: Asking a Question A good testable question should include a cause and an effect. A good testable question will focus your testing to only one factor. For example, asking the question, "What is the effect of sunlight on the growth of plants?" instead of "What affects the growth of plants?" will allow you to make predictions, create a plan, conduct a fair test, and make meaningful observations and conclusions. Example: Testable Question What is the effect of the application of heat on the viscosity of a fluid? C The above question includes the cause (application of heat) and the effect (viscosity of a liquid). These two portions of the testable question are called variables. Variables are factors that can affect an event or process in some way. The cause portion of the testable question, representing the one thing you purposely change, is called the Independent Variable (IV). The effect portion of the testable question, or the thing you will measure, is called the Dependent Variable (DV). Sometimes placing the variables in the following manner helps to identify each portion: Dependent Variable depends on Independent Variable If we were to apply this approach to the testable question above we might say: The viscosity of a fluid depends on Dependent Variable the application of heat Independent Variable Read pages of Nelson Science and Technology Skills Handbook to learn more about testable questions and their independent and dependent variables.

3 Grade 8 Science Module 1, Lesson If the amount of heat added I increases, then the viscosity j will decrease. Using the example of "how heat affects viscosity": N If the increases or decreases, then the will increase or decrease. A hypothesis is a suggested answer or a prediction of how one variable affects the other. The hypothesis should predict the relationship between the independent and dependent variables. Often it follows this pattern: Step Two: Making a Hypothesis 3. How does the density of a substance affect the angle of refraction of light passing through it? Independent Variable Dependent Variable 2. What is the effect of the level of activity on a person's respiratory rate? Independent Variable Dependent Variable Identify the independent and dependent variables in the following testable questions: 1. What is the effect of the size of the tube on the flow rate of a fluid? Independent Variable Dependent Variable Practice: Independent and Dependent Variables

4 26 Module 1, Lesson 3 Grade 8 Science 0 More examples: increases, then the I respiratory rate temperature of a hockey puck decreases, m number of bounces off the boards decreases. Practice: Creating a Hypothesis C Create a hypothesis statement for the following testable questions. (Reminder: It should include the Independent Variable (IV) and Dependent Variable (DV) you listed above.) 1. What is the effect of the size of a tube on the flow rate of a fluid? Hypothesis: 2. What is the effect of physical conditioning on recovery rate? Hypothesis: 3. How does application of pressure affect the flow rate of a fluid? Hypothesis:

5 Ensuring a Fair Test L3 Grade 8 Science Module 1, Lesson How does the addition of salt affect the buoyant force exerted by water? Controlled variables: Identify the things to control (controlled variables) when investigating these testable questions: 1. How does the speed of a car affect how much gas it uses? Controlled variables: Practice: Identifying Controlled Variables For further information and examples of controls, read pages ofnelson Science and Technology Skills Handbook. To conduct a fair test we must ensure that other factors that may affect the outcome of the experiment are controlled or kept the same. These variables that are not changed are called controlled variables. Think of the experiment to see which sponge absorbs the most. Because a larger sponge would probably absorb more liquid, the size of the sponge used is a variable we would want to control. An identically sized sample of each of the different types of sponges to be tested could be cut out. Then the amount of liquid each absorbed could be compared fairly, with the results attributed to the type of sponge and not the size of the sponge. In the case of "the effect of application of heat on the viscosity of fluid," several variables that you may wish to control or keep the same are the amount of fluid distance the fluids have to travel angle of slope Step Three: Designing the Experiment

6 0 28 Module 1, Lesson 3 Grade 8 Science 3. How does water affect the size of a raisin? Controlled variables: Creating a Plan The next step is to create a plan to test our hypothesis. First we must determine what materials are needed to conduct the test. Then we must create a plan or method. The method should be recorded in numbered steps. To continue the concept of fair test, the test should be done several times. This is to ensure that results did not happen by chance or were a fluke, but are accurate and dependable. Learning Activity: Experimenting with Heat and Viscosity Use the apparatus and method below to test the effect of the application of heat on the viscosity of a liquid. Charts for recording your results are found on pages Apparatus: molasses, teaspoon, cookie sheet and material to prop it up at a slight angle, device to measure time Method: 1. Place a teaspoon of molasses (straight from the refrigerator) on the cookie sheet. 2. Record the time it takes to flow a specific distance. 3. Heat up the teaspoon of molasses for 10 seconds in the microwave or in a container resting in hot water for 1 minute. 4. Place the teaspoon of warmed molasses on the cookie sheet and record its flow rate. 5. Heat up one teaspoon of molasses (from fridge) for 20 seconds in the microwave or place in a container resting in hot water for 2 minutes. 6. Place the teaspoon of warmed molasses on the cookie sheet and record the flow rate. 7. Heat, in microwave, one teaspoon of molasses for 30 seconds or in a container resting in hot water for 3 minutes. 8. Record flow rate.

7 9. Continue tests, raising heating time by 10 seconds for each test up to and including 50 seconds. 10. Repeat tests. Plant 3 - In Shade 1 (2) Plant 1 - In Sunlight lant 2 - In Partial Sunlight 5 3 Plant Growth After 1 Week (cm) (1) Effect of Sunlight on Plant Growth (3) L3 Using page 63 of Nelson Science and Technology Skills Handbook as a reference, identify the components of the following data table using the terms provided on the following page. Observations can be recorded in any of the following ways: written in sentences graphs (handwritten or computer-generated) point-form notes diagrams charts lists spreadsheets Step Five: Observing and Recording Data During the experiment, it is important to follow your plan to take accurate measurements and make careful observations. The safety of yourself and others should always be on your mind. To increase the accuracy and reliability of the experiment, measurements should be repeated. Step Four: Conducting the Experiment Safety Note: This experiment should be done under the supervision of an adult. Grade 8 Science Module 1, Lesson 3 29

8 30 ModuIe I Lesson 3 Terms: dependent variable, unit of measurement, independent variable, title When you have recorded your observations, you might observe patterns and/or discrepancies in your data. These may be recorded in your observations. It is at this time that you may also identify possible sources of error. For example, one plant that was in sunlight may have been exposed to spider mites or disease, resulting in poor growth. Recording Results Record the test results from your experiment on the effect of heat on the viscosity of a fluid. Test #1 Time heated I Length of time to Ranking (1 is the travel 25 cm slowest and most viscous substance) 0

9 Time heated Length of time to Ranking (fis the I travel25cm - -, slowest -and mostviscous substance) 31 0.o Grade If appropriate, data can be placed on a graph to better analyze the results of your experiments. (Refer to page of Nelson Science and Technology Skills Handbook for instructions on creating graphs.) Your conclusion should explain the cause and effect relationship between the independent variable and the dependent variable. For example: In our experiment, all variables, other than the amount of sunlight, were kept constant. The geranium plants that received additional sunlight did grow more than the plants that were only given limited amounts of sunlight. In the 32 days that we ran the experiment, the plants Step Six: Organizing and Analyzing Results Record any possible sources of error that may have affected the outcome of your tests. 0 (right from fridge) 8 Science Module 1, Lesson 3 Test #2

10 32 Module 1, Lesson 3 Grade 8 Science 0: that received an additional 10 hours of sunlight a day grew an average of3 cm, while the plants that received only limited sunlight grew an average of 1 cm. Our results support our predictionlhypothesis. Conclusion Record your conclusions for your application of the heat/viscosity experiment: 0 Maybe you noted in your sources of error that the molasses did not flow in a straight line, but spread. In your Reflections on the Process you may want to suggest ways to improve the testing of the flow rate. You may want to suggest using a channel made of a cross section of tubing or large straw so that the molasses does not have the opportunity to spread but only flow down in the narrow channel. Implications and Applications for Daily Use deals with how this concept can be applied to other instances or events. Knowledge about heat and its effects on the flow rate and viscosity of a liquid may help in deciding what type of engine oil to use in different seasons, for example. You may wish to use less viscous oil in wintertime because the temperatures will cause viscosity to rise and thereby strain the engine. 0

11 Step Seven: Communicating Results 1. is a factor that can affect an event or process in some way. 2. A prediction of how one variable affects the other is called a(n) 3. The part of the experiment that we can change or manipulate is called the 4. is a factor that can be affected because of a change to other variables. 5. is determined by calculating the time it takes a fluid to flow a certain distance. 6. can be recorded as written sentences, graphs, point form notes, diagrams, charts, lists, and/or spreadsheets. 7. To conduct a the investigator must ensure that other factors that may affect the outcome of the experiment are controlled or kept the same. 8. includes a cause and effect relationship to investigate and focuses your testing to only one factor or variable. 9. An explanation of the cause and effect relationship between the independent variable and the dependent variable is included in the Complete the sentences with the choices below (one term is used twice). independent variable hypothesis temperature dependent variable fair test pressure applied controlled variable flow rate/variable conclusion testable question observations tube diameter Questions: Thinking about Scientific Inquiry It is important to communicate results and share with others. This can be done in a variety of ways. Lab Report templates have been provided for you to use for experiments throughout the course. Grade 8 Science Module 1, Lesson 3 33

12 34 Module 1, Lesson 3 Grade 8 Science 10. Variables that are not changed are called The length of time it takes an ice cube to melt would be an example of a(n) 12. Three factors that affect the flow rate of a fluid are C C