Fair Test: What Is the Difference?

Transcription

1 Throughout this unit, you have been presented with the question, How would I make a fair test to compare these 2 objects? Now, it is time for you to show what you have learned by designing and conducting fair tests to demonstrate the difference between the substances (solids, liquids or gases) you have chosen. You may choose more than 2 substances, as long as you control variables in your testing. You may use any of the tests you have learned how to conduct, such as making a fair test for density, a fair test for acids and bases, or a fair test for texture. Remember to identify and control variables during your tests. You will be sharing your experimental design and results for 3 tests conducted. Make sure you can present them in graph form when you are finished collecting your data. 1 of 17

2 Suggested Grade Span 3 5 Task Throughout this unit, you have been presented with the question, How would I make a fair test to compare these 2 objects? Now, it is time for you to show what you have learned by designing and conducting fair tests to demonstrate the difference between the substances (solids, liquids or gases) you have chosen. You may choose more than 2 substances, as long as you control variables in your testing. You may use any of the tests you have learned how to conduct, such as making a fair test for density, a fair test for acids and bases, or a fair test for texture. Remember to identify and control variables during your tests. You will be sharing your experimental design and results for 3 tests conducted. Make sure you can present them in graph form when you are finished collecting your data. Big Idea and Unifying Concept Cause and effect Physical Science Concept Properties of matter Mathematics Concepts Data collection, organization and analysis Graphs, tables and representations Patterns Time Required for the Task One week. Context As a team-taught class of 50 students, we are finishing up a unit on the chemical and physical properties of matter. Students have completed experiments and activities and have seen 2 of 17

3 demonstrations involving density, hardness, bouncibility, ph, solubility, simple chemical reactions, simple physical changes and melting point, as well as color, texture, volume and mass. Throughout the unit, we have also concentrated on what constitutes a fair test. What the Task Accomplishes This investigation gives students the ability to choose substances and conduct fair tests on what they choose to distinguish each substance from the other(s). It teaches students properties of items not yet tested in class, as well as how to relate the activities they have done in class to substances of their choosing. As students choose three tests to conduct and complete, the assignment reinforces what they have learned about chemical and physical properties. This inquiry task assesses their knowledge of these properties, as well as their knowledge of fair tests and of properties of matter. How the Student Will Investigate Many times throughout the unit, the students have been presented with the question, How would I make a fair test to compare these two objects? I refresh their memories on these demonstrations and discussions before passing out this assignment. For example, if making a fair test of density, I review the activity we did with a density column. We then read the assignment together, stressing that they need to show three tests to demonstrate the difference between the objects (or among the objects if they choose more than two). On the first day, students complete the first part of their worksheet by identifying what they will test and how they will test it. That is handed in and checked by the teacher before students begin the next day. Data are then collected for three tests over the next two class periods. For each test, a graph is created displaying data collected. Graphs are drawn on large paper for (four-minute) presentations on the last day of class. Interdisciplinary Links and Extensions Science Students can critique the fairness of tests conducted by their classmates and compare results when several students conducted similar tests with the same substances. Language Arts Students practice speaking and listening skills when they present their findings to the class. Students develop and organize information to be presented in a logical manner so that the audience can understand the test design and the results of tests presented. Mathematics Students create graphs for each of the three tests conducted. Graphs must be correctly labeled and large enough for the audience to see them clearly. 3 of 17

4 Teaching Tips and Guiding Questions Make sure the students check in with you before they begin experiments on certain substances. As there can be many hazards with mixing materials or choosing dangerous items such as glass, all preliminary work should be first checked with you. Once students have their substances, they should first determine fair tests that can be completed for their substances. (For example, bouncibility might not be a good test for two liquids.) Also, these tests should have the ability to translate to graphs for the presentations. Questions for students to consider include: Do you have all the materials you need? Are you clear on the steps you will take? How will you control variables? How will you record your data? How will you present your information? How will you label your graph? What do you think would be a specific test for these objects? Would you want to find out about the melting point? density? hardness? Concepts to be Assessed (Unifying concepts/big ideas and science concepts to be assessed using the Science Exemplars Rubric under the criterion: Science Concepts and Related Content) Scientific Method: Students observe and explain reactions when variables are controlled (cause and effect). Using data and prior knowledge, students describe cause-effect relationships with some justification. Physical Science Properties of Matter: Students compare physical properties of matter. Students observe and measure characteristic properties of matter (e.g. boiling point, melting point, density, buoyancy, simple chemical reactions) and use them to distinguish one substance from another. Students use the terms acid/base, density, hardness, melting/boiling points, fair test, variable, etc. appropriately. Mathematics: Students represent and analyze data appropriately and use tables and graphs to show how values of one variable are related (increase, decrease, etc.) to values of another. Students identify trends and patterns. Skills to be Developed (Science process skills to be assessed using the Science Exemplars Rubric under the criteria: Scientific Procedures and Reasoning Strategies, and Scientific Communication Using Data) Scientific Method: Observing, predicting/hypothesizing, collecting and recording data, manipulating tools, drawing conclusions, communicating findings, challenging misconceptions and raising new questions. 4 of 17

5 Other Science Standards and Concepts Addressed Scientific Method: Students describe, predict, investigate and explain phenomena. Students control variables. Scientific Theory: Students look for evidence that explains why things happen and modify explanations when new observations are made. Physical Science Properties of Matter: Students describe and sort objects and materials according to observations of similarities and differences of physical properties. Students understand that properties and changes of properties in matter can cause changes in ecosystems. Suggested Materials Have on hand any materials that you have used for previous activities and experiments. I usually have cabbage juice (ph), Karo syrup, dish detergent, water (to test density), a balance scale, meter sticks and water (to test if something rusts) as well as beakers and other containers for measuring, heating liquids, and mixing substances together. Other measuring devices to have available might include meter sticks, measuring tapes, timers and rulers. Possible Solutions Solutions will vary with the substances chosen. There needs to be evidence of data collected and displayed in a labeled graph, three appropriate tests conducted, and variables controlled. Note: Graphs are not shown here due to the large size. Task-Specific Assessment Notes Novice The student completes only one test on the materials. The problem identifies a variable to test (mass) and the hypothesis is clearly stated, but the procedure and conclusion lack definition. There is no explanation as to what is done to test for mass, only which substance has the most mass. The conclusion is based on knowledge available before doing the experiment, not from the experiment itself. A graph is drawn but lacks labels. Apprentice This student completes the three tests on the materials. There is a defined problem and hypothesis. The procedures have enough detail for the reader to understand what is done in each test, yet they are still quite vague for some of the tests. No timer is used in recording data for one test. Some data are recorded, but no conclusions are given for any of the tests. The graphs are drawn and labeled, but some labels are incorrect. 5 of 17

6 Practitioner This student s solution is complete, although only one of the three tests is shown here. The procedure shows a clear explanation of what the student did. Observations are complete, and a diagram is included to show what it looked like. The conclusion is based on the data and relates back to the problem and hypothesis. The graph is labeled and complete. Expert This student s experiments are well-detailed. (Only one of the tests is included due to the length of each write-up.) Although the materials are not listed, they are written in the procedure. The steps are in an order that is easy to follow. The conclusion/explanation of tests shows that the student ran the test more than once. Explanations show that the student knows what acids/bases (or whatever the student is testing) are. The conclusion is supported by data. The graph is labeled correctly and displays the information clearly. 6 of 17

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