Hot-water and warm-air heating systems burn fuel for thermal energy, transfer the energy to water or air, and circulate the water or air throughout the house. Cooling systems such as refrigerators reverse the normal direction of heat flow by doing work. They use a refrigerant to transfer thermal energy from the refrigerator to the room. A combustion engine burns fuel to produce thermal energy and then uses the thermal energy to do work. Combustion engines may by external or internal combustion engines, depending on where the fuel is burned.
- Identify common home heating systems.
- Explain how a cooling system transfers thermal energy.
- Outline how a combustion engine works.
combustion engine: complex machine that burns fuel to produce thermal energy and uses the thermal energy to do work
refrigerant: substance with a low boiling point that is used to transfer thermal energy in a cooling system such as a refrigerator
Introducing the Lesson
Demonstrate the use of hot air and hot water with a hair dryer and hot water bottle. Ask students if they can think of other ways that hot air or hot water can be used. Tell them they will learn in this lesson how hot air and hot water can be used to heat a house.
Use simulations to help students understand how thermal energy is used in the home. You can find two examples at the URLs below. The first animation demonstrates how a solar water heater works. The second animation demonstrates how a thermostat controls a home heating system.
Use the excellent animations at the following URLs to demonstrate how external and internal combustion engines work. Along with the animations, the Web pages include a step-by-step illustrated explanation of how the engines work.
Use the lesson diagram showing how a refrigerator works when you explain how a cooling system transfers thermal energy. Show students the animated version of the diagram at this URL: http://www.ior.org.uk/ior_/fantastic_fridges_site/science/fridge1/fridgediag.htm.
Before students read the lesson, have them think about how thermal energy might be used to heat a home or run an automobile. After they read the lesson, pair English language learners with native English speakers, and have partners discuss the ways of using thermal energy that they read about in the lesson.
Ask one or more interested students to interview an automobile repair technician or other expert about how an internal combustion engine works. They should prepare a list of questions in advance. Have the students summarize what they learn in an oral presentation to the class.
Students can explore the use of thermal energy from the sun by building and using a solar cooker. The activity will teach them the basic principles of solar-thermal and passive-solar heating.
Suggest that students learn about the heating system in their own home. Through inspection and asking parents or other adult members of the household, they should find out which type of heating system it is and, if it burns fuel, which type of fuel it uses. They also might learn how the fuel is stored or supplied, where heating vents or radiators are located, and the locations of ducts or pipes.
Reinforce and Review
Copy and distribute the lesson worksheets in the CK-12 Physical Science for Middle School Workbook. Ask students to complete the worksheets alone or in pairs to reinforce lesson content.
Lesson Review Questions
Have students answer the Review Questions listed at the end of the lesson in the FlexBook® student edition.
Check students’ mastery of the lesson with Lesson 18.3 Quiz in CK-12 Physical Science for Middle School Quizzes and Tests.
Points to Consider
In this chapter, you read that thermal energy can travel in waves by radiation. You can learn more about waves in Chapter 19.
- What other forms of energy travel in waves? (Hint: How does sound energy travel?)
- Think about ocean waves. How do the waves move? How do you think they carry energy?