Heat Transfer. Leslie Van Montgomery Blair High School Silver Spring, Maryland Summer 2005

Transcription

1 Montgomery Blair High School Silver Spring, Maryland Summer 2005 Research Host: Dr. Margery Anderson Dr. Maria Mayda Walter Reed Army Institute of Research Lesson # 17

2 Appropriate citation: Van, Leslie (APS Archive of Teaching Resources Item #7306. [Online]. Bethesda, MD: American Physiological Society, Editor s notes: Website URLs listed in this resource were current as of publication, but may now be obsolete. If you know of a replacement URL, please suggest it in the resource s Comments section. Safety Concern: Teacher should provide proper supervision when hot materials are being used. Disclaimer: This activity was created by the author and reviewed by the American Physiological Society. Any interpretations, statements, or conclusions in this publication are those of the author and do not necessarily represent the views of either the American Physiological Society or the funding agencies supporting the professional development program in which the author participated. Frontiers in Physiology The American Physiological Society Permission is granted for workshop/classroom use with appropriate citation

3 Teacher Section Purpose The purpose of this activity is to explore how heat can be transferred from one substance to another. Each section of the activity will introduce a new level of inquiry. The first part is a demo on convection to help the students get used to proper procedures in scientific inquiry. The second part is a cookbook lab on radiation so students can practice proper laboratory skills. The third part is a guided inquiry on conduction that can be adapted into an open inquiry that allows the students to come up with their own question, hypothesis, and procedure. Objectives The students will be able to Describe heat transfer through conduction, convection, and radiation Formulate and test a hypothesis Identify appropriate methods for conducting an investigation Use relationships in the lab to explain phenomena observed outside the laboratory Grade Level 9 th grade physical science National Science Education Standards Grades 9-12 Science as Inquiry Abilities necessary to do scientific inquiry Understandings about scientific inquiry Physical Science Interactions of energy and matter Maryland Science Education Standards HS HS1.2.1 HS1.2.2 HS1.2.3 HS1.2.4 HS1.2.5 HS1.2.6 HS1.2.7 HS1.3.1 HS1.3.2 Explain how differentials in energy can result in energy transfer Identify meaningful, answerable scientific questions. Pose meaningful, answerable scientific questions. Formulate a working hypothesis. Test a working hypothesis. Select appropriate instruments and materials to conduct an investigation. Identify appropriate methods for conducting an investigation. Use relationships discovered in the lab to explain phenomena observed outside the laboratory. Develop and demonstrate skills in using lab and field equipment to perform investigative techniques. Recognize safe laboratory procedures.

4 Teacher Section Prior Knowledge Students should understand heat as a form of energy. We do this lesson after discussing the different forms of energy and conservation of energy. They need to know that molecules are in constant motion, but the term kinetic molecular theory is not necessary. Density vocabulary and concepts may arise in explaining why warm fluids rise and cold fluids sink. Including All Students Heat is all-pervasive. All students can relate to how heat affects their lives. On the other hand, different cultures deal with heat differently, especially when its weather related. Students can choose their own topic to research and are encouraged to choose something with which they are familiar. Students are provided with a variety of ways to demonstrate their understanding in order to cover all types of learning intelligences. Questions to Ask Along the Way 1) Why does snow on asphalt roads melt faster than snow on cement? 2) How do greenhouses work? 3) How do you warm your house? How do you prevent heat loss? 4) Why are pipes in solar panels painted black? 5) Why are radiators placed on the floor of a room? 6) Where are the heating vents in the classroom or your house? Why are they in these locations? Does this work better for heat or air conditioning? 7) Discuss making observations and forming hypotheses. 8) Discuss the idea of testing one variable at a time and the difference between independent variables and dependent variables. 9) What did you observe? What patterns did you find? What might be the cause? 10) How do your results compare with what you expected? Materials Convection demo 500mL beaker Food coloring for ice cubes Thermometer Hot plate Student handout Radiation cookbook lab Black tin cup Silver tin cup Two thermometers Large desk lamp Styrofoam caps for cups Student handout provided Conduction guided inquiry Cubes made of different types of metal Bunsen burner/hot plate Wax Beakers Thermometers Conductivity wheel Water Other materials will depend on groups procedures Student handout provided

5 Teacher Section Safety Students need to get teacher approval of their procedure before beginning. All testing must be done under strict teacher supervision to avoid any potential problems. Students should abide by all laboratory safety policies established in the classroom. Heat is a major factor in this unit, so a special reminder about working with Bunsen burners, hot plates, etc. will be useful. Procedure Part 1 Intro to (Engage 10 min) Start with a discussion of how things get hot. Brainstorm ideas. If you want to guide students towards the three different methods of heat transfer, you can group the ideas they come up with and then ask them why they think their ideas are grouped in this manner. You can do this as a whole class or you can give each student a few index cards, have them write down the ideas, and then stick the ideas to the board. Part 1, contd. Convection Demo (Explore 30 min, Extend/Evaluate 5 min) You need to have made ice cubes with colored water. The more concentrated the food coloring, the darker the ice cube will be, and the easier it will be for the students to see the effect. Fill a 500mL beaker with hot water. If you do not have a hot water faucet in the classroom, you can heat the water up on a hot plate. It does not have to be boiling water, but hotter water has a more dramatic effect. To begin the demo, ask the students to observe the ice cube and the beaker of water. You will need to take the temperature of the water and ice cube if the students don t suggest it first. Then hypothesize what will happen when you put the ice cube into the water. Write down observations and hypotheses on the board. Students will compile all information from the demo on a corresponding worksheet (see Student Section). Ask for a student volunteer to take temperatures. Have the other students write down observations and draw a picture of what they see happening. Gently place the ice cube into the water. It may be useful to place the beaker of water on the overhead with the light on so students can see the water more clearly. Technically, they should be able to see the colored water sink to the bottom of the beaker as the ice cube melts. Depending on how big your ice cube is students may also see the water at the bottom of the beaker begin to flow back up to the top. After 10 seconds, have the student volunteer take the temperature of the water at the surface of the beaker and at the bottom of the beaker. Take the temperatures again after 1 minute. Take the temperatures once more when the ice cube has completely melted. Have volunteers draw their observations on the board. Discuss their drawings and the temperature data. Talk about how heat was transferred in the demo. Introduce the concept of convection. Write down any conclusions, sources of error, and room for improvement on the board. Depending on how much time you have left in the period, you can brainstorm ideas on how to test any new questions the students may have come up with. As an exit card, have students write what they think the definition of convection is and give you another example of when convection occurs.

6 Teacher Section Part 2 Radiation Cookbook Lab (Explore 45 min, Evaluate - homework) Begin by asking students how the sun heats things up. Some of these issues may have already been addressed on during Part 1 of this unit. You can ask them some of the suggested questions below to jumpstart the conversation. Hand out the student lab instructions and materials. It shouldn t take them more than 30 minutes to complete the procedure. They can start the lab analysis questions if they have time during class and finish them for homework. Part 3 Conduction Guided Inquiry (Explore min, Evaluate - homework) Students will explore how heat is transferred through direct contact. Each group of students will be given a certain set of materials and be asked to design and carry out a procedure that answers the question: What type of metal would be the best at heating materials? If students are confused about this, a conversation about what things are made of metal and why they aren t made of some other type of metal (i.e. cooking utensils, pots and pans, etc.) might help. For students who are having difficulty coming up with a procedure, you may want to guide them towards using the conductivity wheel. The materials available at your school will also affect what kind of lab the students can design. Students and teachers should use the checklist provided to track their progress in setting up their experiment and getting their procedure approved. The students should be monitored carefully as they carry out their experiment. You will want to limit the length of each experiment so this does not take more than 90 minutes to complete. To assess, have students individually write a paragraph abstract on their experimental design using the class discussion from Part 1 as a guide. Finally, they will create a poster to present their experiment to the rest of the class, according to the rubric in the student section. You could also make this an open inquiry about conduction of any materials. Part 4 Researching (Extend/Evaluate 45 min + HW or 90 min + HW) Students will be researching a common appliance or natural phenomenon that illustrates the concepts of heat transfer. They will be writing a standard five-paragraph paper, so individual topics may be the most appropriate. Depending on the size of your class, duplication of topics is probably inevitable. Students may come up with their own ideas for research. Just make sure their topics have to do with heat transfer and the information is readily available. Students will start their research on the How Stuff Works website, Each website they visit will be evaluated according to the Website Evaluation worksheet in the student section. The worksheet will also prompt them to collect all the information they will need to properly cite their sources. They need to find all the information necessary to answer the questions to complete their paper. Paper details, including rubric, are in the Student Section. Students can also use any other sources (books, magazines, etc.) as long as they remember to cite them. Talk to your media center specialists they may have a lot of resources for the students to use. Books like David MacCauley s The Way Things Work are very useful.

7 Where to Go From Here Part 4 (the research paper) is the extension of the inquiry lab on heat transfer. If you wish to go further than this, depending on your curriculum and how much time you have, environmental concerns are always a relevant topic. Global warming, increase in ocean temperatures leading to the melting of the polar ice caps, heat production (coal burning, heat/ac systems, etc.), energy conservation, and alternative energy sources can all be discussed. Students can do background research on heat transfer and additional research on other topics not discussed in class, read articles, and debate the hot topics. Suggestions for Assessment Rubrics for the lab design (Part 2), poster (Part 3), and research paper (Part 4) are included in the Student Section. It is also feasible to collect all the steps of this lesson into a portfolio to be evaluated at the end of the lesson or at the end of a grading period so students can examine their work and see what they ve accomplished. References and Resources How Stuff Works ( MacCauley, David. The Way Things Work. Teacher Section

8 Student Section Convection Demo Practice analyzing an experiment Observations and diagram of demo set-up: Hypothesis: Observation and diagram of demo results: Temperature data: Temperature ( C) At 10 seconds At 1 minute Top of beaker Middle of beaker Bottom of beaker After ice cube melted Conclusions (What happened and why): Sources of error and room for improvement: New questions?

9 Student Section Designing a Scientific Investigation You will be working in groups of three to investigate how different types of metal affect heat conduction. As a group you will decide how to test the question, What type of metal would be the best at heating materials? You will have a variety of metal objects to perform your tests on. You will need to propose a hypothesis, state the independent and dependent variables and constants, and write out a step-by-step procedure before beginning your experiment. Today: Get into your groups to do the tasks listed below. There are certain check points when you must see me at before you can move on. 1. Phrase (state) a purpose or question. 2. State a hypothesis. Checkpoint #1 3. State the Independent Variable, Dependent Variable, and constants. 4. List the materials you will use. 5. Develop a detailed, step-by-step procedure. Checkpoint #2 6. Design a data table into which you will record your data. Checkpoint #3 Checkpoint #4 Next Class: Next class you will perform your experiment that your group has designed.

10 Student Section Rubric for Scientific Investigation Names of group members: Title: Is present, clear, and gives insight to what the experiment is about /2 Purpose: Clearly states what the purpose of the scientific investigation is Hypothesis: Is present and has been thoroughly developed Materials: All materials used are listed IV/ DV /Constants: Present, correctly stated, well thought out Procedure: Listed step-by-step, detailed, easy to follow Data Table/Data: Contains a well-designed data table for the scientific investigation Data and observations are present and detailed /2 /3 /3 Conclusion: Contains a summary of what was observed. Contains a conclusion about how the variable tested relates to heat transfer Well organized, complete sentences used. Analysis: Was the hypothesis right or wrong? Why? What errors were made? If the investigation were to be done again, what changes would be made? Well organized, complete sentences used. Appearance/neatness Report to class: What was investigated? What was observed and concluded? Total: /45

11 Student Section Different Strokes: An Exploration of Introduction: When substances come in contact, their molecules interact with each other and heat is transferred by conduction. Conduction most commonly occurs between two solids. Another form of heat transfer is called convection. Convection is the transfer of heat energy by movement of fluids or gases in a pattern called convection currents. The convection current is the movement that occurs as warm fluids or gases rise and cool fluid or gas sinks. Convection currents involving gases occur frequently in weather patterns as warm air masses collide with colder air masses. The third kind of heat transfer, radiation, involves the movement of heat energy by infrared waves. Unlike other forms of heat transfer, radiation can occur in a vacuum. A vacuum is an area of space that does not contain matter. The absorption of heat through the air is another example of radiation. Purpose: To explore how can heat be transferred from one substance to another. Materials: silver and black radiation cups with lids 2 thermometers lamp Procedure: 1. Place thermometers in the empty silver and black cup and secure them with an insulated lid. 2. Record the initial temperatures on each thermometer (temperatures should be the same). 3. Place both cups in equal distances from a light source. Turn the light so it shines equally on each cup. 4. Record the temperatures inside the cans every 30 seconds for two minutes with the light on. (Keep the light on the whole two minutes!) 5. Turn off the light. 6. Record the temperatures inside the cans every 30 seconds for two minutes with the light off. Table 3 Radiant Energy Transfer Time Temperature Taken Silver Cup Black Cup initial 30 sec w/ light on 1 min w/ light on 1 min, 30 sec w/ light on 2 min w/ light on 30 sec w/ light off 1 min w/ light off 1 min, 30 sec w/ light off 2 min w/ light off Analysis and Conclusions: 1. Heat is transferred from the sun to the earth through space. Space is a vacuum, an area with no molecules. By what method does the sun s heat reach the Earth? 2. Why is summer clothing usually made of lighter-colored materials than winter clothing?

12 Student Section Uses of Heat Research Paper When you rub your hands together, the friction you create causes heat. When we are cold, our body senses our need for heat and causes us to shiver, an act that generates internal heat to keep our bodies warm. When substances come in contact, their molecules interact with each other and heat is transferred by conduction. Conduction most commonly occurs between two solids. Another form of heat transfer is called convection. Convection is the transfer of heat energy by movement of fluids that occurs as warm fluids rise and cool fluid sinks. The third kind of heat transfer, radiation, involves the movement of heat energy by infrared waves. In today s society, heat is one of the most often utilized forms of energy. Your research project will involve the study of how heat is involved in various aspects of your lives. Below is a list of household appliances, commercial items, or natural events that involve heat transfer: Air conditioner Clothes dryer Fans Coffee maker Car engine Ovens/Stoves Thermometers Hair dryer Greenhouse effect Lasers Thermos Hurricanes Microwave oven Refrigerator Gas lantern Thermostat Toaster Gas grill Water heater Lava lamp Hot air balloons You are to select one of these topics or choose another topic (to be approved by the teacher) and study it. You will then write a short paper about the appliance you studied. The paper should include answers to the following questions: How does the appliance/event work? What kind of energy does it use to produce heat? How is this heat transferred within the appliance/event? The following is a grading rubric for the paper specifying how the paper will be graded. Explanation of how the appliance/event works (10 points) How and what types of energy are used to produce heat (10 points) How heat is transferred within the appliance/event (10 points) Neatness and logical order of ideas (5 points) APA style bibliography (5 points) TOTAL: 40 points

13 Student Section Web Site Evaluation Form General Information: 1. URL of the Website: 2. What is the top level domain of this website? Choose one of the following:.edu.k12.gov.org.com.net other? 3. Website Title: Authorship: 4. What organization and/or individual created this website? 5. Can you rely on this information? Yes No Why or why not? 6. Is contact information provided? Place an X next to all that apply. address telephone number mailing address contact name Content: 7. What is the main purpose of the site? Place an X next to all that apply. to inform to persuade to sell a product Other 8. Is there advertising? yes no Is it distracting? yes no 9. Is the material: Primary/Original Secondary/Derived? Currency: 10. When was this page written or last updated? Your Evaluation: 11. Please rate this web page. use with caution good, basic information excellent for the assignment