1. Chapter 22 Review and Study Guide: Heat Transfer

2. Describe the three methods of heat transfer and give one example of each. Conduction: atoms and free electrons bump into one another; metals are the best conductors because they have loose/free outer electrons Convection: molecules move from place to place; occurs in fluids (liquids and gases) Radiation: energy is transferred by electromagnetic waves, travels through a vacuum; the sun, a fire place, campfire

3. What are two more differences between conduction and convection. Conduction –Atoms and free electrons bump into one another –Metals are the best –Atoms do not leave their spaces Convection –Molecules move from place to place –Happens in fluids –Winds occurs due to convection –Convection currents

4. Heat transfer by convection occurs in what states of matter? Liquids and gases (fluids)

5. What happens to the temperature of a gas when it expands? It decreases. A gas cools when it expands because the molecules are farther apart.

6. Explain the difference between a conductor and an insulator and give three examples of each Conductors –loose outer electrons –conduct heat well –Metals: silver, copper, aluminum, iron Insulators –tightly-bound electrons –delay the flow of heat –air, fiberglass, feathers, snow, fleece, glass, rubber, plastic

7. How does energy travel form the sun to the earth? By radiation in the form of electromagnetic waves.

8. By what method of heat transfer does the earth “lose” heat? Radiation in the form of electromagnetic waves This is called terrestrial radiation.

9. Is black a good absorber of radiation? Yes

10. If something is a good absorber of radiation, is it also a good emitter? Yes (black)

11. Would your hot beverage cool down faster in a black or white mug? In a black mug because black is a good emitter.

12. Why is it a good idea to wear light- colored clothes on a sunny summer day? Because light colors, white is the best, are good reflectors of radiation.

13. What is Newton’s law of cooling? The rate of cooling is depends on the temperature difference between the object/substance and its surroundings. To put it simply, hot objects will cool down faster in a cooler environment.

14. Will a hot apple pie cool down faster on the top of the stove or on the window sill? On the window sill because there’s a greater difference in temperature.

15. Describe the greenhouse effect. Short wavelength radiation from the sun passes through the atmosphere and is absorbed. Energy changes to longer wavelengths (heat) and radiates up through atmosphere. Some long wavelengths get trapped in the atmosphere (greenhouse gases) causing the greenhouse effect.

16. Why does the metal part of your desk feel colder than the top, plastic part? Because the metal part is a good conductor.

17. Why don’t the sides of a burning candle flame feel hot? Because the hot air rises due to convection.

18. What causes ocean breezes during the day? The warmer air over the beach rises and is replaced by the cooler air moving from over the ocean. These are convection currents.

19. Which will cool down faster, hot tea in a silver pot or hot tea in a black pot? The hot tea in the black pot because it’s a good emitter of heat.

20. Why can professional firewalkers walk on hot wooden coals? Because wood is a poor conductor of heat. Wood is an insulator of heat.