Lesson Plan: Designing & Engineering a Fast Defroster for the Forgetful Chef FOR THE TEACHER Summary In this activity students use their understanding of energy transfer to “design a solution to a complex real-world problem, based on scientific knowledge, student-generated sources of evidence, prioritized criteria, and tradeoff considerations.” And “evaluate a solution to a complex real-world problem, based on scientific knowledge, student-generated sources of evidence, prioritized criteria, and tradeoff considerations.” The real world problem is to help a cook who is trying to make a meal, but realizes some of the ingredients are frozen and must be thawed before he can begin.
Submitted by ACS High School Professional Development Team Washington, D.C.
Grade Level Middle and High School NGSS Standards ● MS-PS1-4: Develop a model that predicts and describes changes in particle motion, temperature, and state of a pure substance when thermal energy is added or removed. ● MS-PS3-2: Develop a model to describe that when the arrangement of objects interacting at a distance changes, different amounts of potential energy are stored in the system. ● HS-PS3-2: Develop and use models to illustrate that energy at the macroscopic scale can be accounted for as a combination of energy associated with the motions of particles (objects) and energy associated with the relative position of particles (objects). Science & Engineering Practices (SEP) • Designing solutions (for engineering) • Engaging in argument from evidence Crosscutting Concepts (CCC) • Energy and matter: Flows, cycles, and conservation Objectives By the end of this lesson, students should be able to ● Apply scientific ideas to design, test, and refine a device that transfers thermal energy from one substance to another. ● Use tools and materials to design and build a device that speeds the defrosting of frozen foods. Chemistry Topics This lesson supports students’ understanding of ● Heat ● Energy Transfer ● Properties of Matter ● Thermal Conductivity ● Density ● Specific Heat Capacity ● Engineering Design
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Time Teacher Preparation: 30 minutes Lesson: • Introduction and Design Phase: 50 minutes • Building Phase: 30-50 minutes • Testing Phase: 30-50 minutes • Re-Design Phase: 30-50 minutes Materials ● Student Handout ● Power Point Slides ● Various construction materials: foam board, aluminum foil, ceramic plates, ceramic tiles, plastic plates, wood blocks, wax paper, paper plates, plastic wrap, copper sheets, zinc sheets, steel pans ● IR Thermometers (like Thermoworks IR Pocket Thermometer) ● Ice ● Paper Towels ● Student Whiteboards and Markers (or chart paper and markers) Safety • Always wear safety goggles when handling chemicals in the lab. • Students should wash their hands thoroughly before leaving the lab. • When students complete the lab, instruct them how to clean up their materials and dispose of any chemicals. Teacher Notes Course Sequence Suggestion • This lesson follows the lesson plan “What Makes Something Feel Warm? Modeling Energy Transfer: A Macroscopic and Particulate View”. Students will be provided the opportunity to use their knowledge of materials to design a device that will defrost quickly. Instructors may choose to have student engage in all parts of the engineering cycle, or focus on a particular phase, depending on time and needs of the students. Background Information for Teachers • Design: While many teachers have included scientific inquiry and experimental design into their courses, the engineering design practice may be new to most. This practice calls on students to “design a solution to a complex real-world problem, based on scientific knowledge, student-generated sources of evidence, prioritized criteria, and tradeoff considerations.” And also to “evaluate a solution to a complex real-world problem, based on scientific knowledge, student-generated sources of evidence, prioritized criteria, and tradeoff considerations.” • Keep in mind that there are a number of ways in which you can scaffold ideas of designing solutions, depending on their prior experiences. In our experience, less is really more. Providing as little guidance in the design phase, often leads to a greater diversity in solutions. • Students will want to immediately make designs without articulating why they are making the design choices. You might want to have all students make a design individually, and then as a group of four, come to consensus on one design BASED on evidence from the earlier experiments.
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The initial materials that you provide for students to choose need to be safe and appropriate for this activity. They may not necessarily be the best choice for a defroster. A list of materials is provided, but add or substitute materials based on available supplies and your best judgment. Students should only test one variable at a time. Depending on the level of your students’ experience, you may need to provide scaffolding for the experimental design. You may also need to provide hints to students to display the results of their tests. For example: A paper towel might be useful as a way to measure the extent of melting. o Draw a circle on the paper towel with the ice in the center and time how long it takes for the water to reach the circle o Allow the ice to melt for a certain amount of time then outline on the paper towel how far the water reached You might want students to take a digital photo of their prototype to include with their results. Students may want to take the mass of the ice before using the defroster, and have the ice stay in the defroster for a given amount of time. Pat the ice dry and measure the mass after.
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Student Prerequisite Information: Students should have an understanding of thermal conductivity, temperature, and heat (see the lesson plan “What Makes Something Feel Warm? Modeling Energy Transfer: A Macroscopic and Particulate View”).
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Instructional Notes and Answers: Refer to the downloads box for possible responses to the student questions. Keep in mind that in many of the questions, the answers may vary and are not limited to what is provided in this teacher’s guide.
FOR THE STUDENT Lesson
Designing the Fast Defroster for the Forgetful Chef Learning Objectives • •
Students will apply scientific ideas to design, test, and refine a device that transfers thermal energy from one substance to another. Students will use tools and materials to design and build a device that speed the defrosting of frozen foods.
For this part of the lesson, we will be using the NGSS Engineering Design Cycle:
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Step 1: Instructions, Defining the Problem, Developing Solutions Your to: • • • • •
job is to design an effective defrosting device. Keep in mind that you will need Explain why you are choosing the materials that you want to use. Test the device using the testing protocol that the class agrees on. Test one other device and provide feedback to the design team so that they might make modifications. Once you have your own test results, and feedback from another team, you will be required to make some modifications and re-test your device. You will have a variety of materials to use.
1. Write down your initial ideas about the materials that you want to use and explain why you are choosing these materials based on the ideas that you uncovered in the first part of this session.
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Step 2: Building Using the plan you decided upon with your group, build your 2 prototypes. Step 3: Optimizing: Testing Protocol In your design teams, brainstorm testing strategies to present to the class. We will engage in a class discussion that will generate our testing protocol. 2. Record the protocol here:
Step 4: Optimizing: Testing and Comparing Solutions Test your prototype. Make sure your results are reliable and reproducible.
3. Record results and analysis of your testing. 4. Describe any modifications you would make to your plate if you had any other necessary resources available.
Repeat for a prototype from another team. Provide the other team with the data generated in testing, as well as any suggestions for improvement. Step 5: Optimizing Make modifications to your device, and re-test.
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Record your observations.
6. Did the modifications help? Defend your answer.
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7. Do you think you could make more modifications if you had the time? If so, what would they be?
Analysis Questions 8. Based on your experiment and your models, describe how thermal energy is transferred.
9. Are there possible aspects of thermal energy transfer that your model did not account for?
10. During the engineering process, did your ideas about thermal energy transfer change? Explain.
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Assessment 11. Think again about the Forgetful Chef warm up question. Which of the following materials would you suggest the chef use to defrost the chicken? Use your model, ideas from this activity and the data in the table below to support your response. o Wooden Butcher Block o Granite countertop o Aluminum baking pan o Glass bowl o Plastic container with cold water o Kitchen towel
Material aluminum Water Wood, white oak Glass, pyrex Granite Wool, Felt Cotton
Thermal Conductivity (W/mK)
Specific Heat Capacity (J/g 0C)
Density (g/cm3 )
237 0.6 0.209 1.13 2.51 0.07 0.04
0.90 4.18 2.39 0.73 0.75 1.38 1.30
2.70 1.00 0.83 2.22 2.65 1.31 1.56
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