4. More energy will be transferred between water at 10 C and a freezer at 15 C because the temperature difference is greater.

Transcription

1 Section Review Answers Chapter 14 Section 1 1. Absolute zero is the temperature at which particles have theoretically zero kinetic energy. 2. The higher temperature of the hot soup means that the water molecules in the soup will move faster on average than the water molecules in iced lemonade. 3. Temperature is a measure of the average kinetic energy of particles of a substance. The higher the kinetic energy of particles is, the higher the temperature is. 4. More energy will be transferred between water at 10 C and a freezer at 15 C because the temperature difference is greater. 5. A cup of boiling water has a higher temperature and thus higher average kinetic energy than Lake Michigan has, but Lake Michigan has more total kinetic energy (and thus more heat) because it has more particles (20.0) = 68.0 F = 293 K 7. ( )/1.8 = 89.2 C = 184 K Section 2 1. Energy transfer by conduction involves direct contact. Higher-energy molecules transfer energy to lower-energy molecules. Energy transfer by convection involves the movement of the higherenergy molecules from one place to another. Energy transfer by radiation involves the emis-

2 sion and absorption of electromagnetic waves. 2. The hottest part of the room should be near the ceiling because hot air rises. 3. The temperature differences on the moon s surface are due to two factors. One is the varying composition of the moon s surface. The other factor is the location of the spot, whether it is in the sun or covered by shade. 4. The cookies near the turned-up edge receive conduction energy from the cookie sheet, just as the cookies in the middle do. However, those near the edge also receive energy from air convection currents and radiation from the side. 5. energy = (385 J/kg K)(0.55 kg)(45 C 24 C) = 4,400 J 6. energy = (449 J/kg K)(144 kg)(35 C 25 C) (1 kj/1000 J) = 650 kj 7. energy = (4186 J/kg K)(2 kg)(355 K 298 K) = 4.8 _ 105 J Section 3 1. Sample answer: The first law of thermodynamics states that energy from heat always goes somewhere rather than being created or destroyed. The second law of thermodynamics states that heat always tends to go from an area of high temperature to an area of low temperature. 2. The disorder of a system will increase over time if the system is left to itself. 3. Sample answer: Entropy is the amount of randomness in a region.

3 4. The two types of heat engines are the internal combustion engine and the external combustion engine. 5. The second law of thermodynamics requires that the output energy of a heat engine always be less than the energy put into it. 6. Sample answer: I transfer kinetic energy when I pedal my bicycle. The first law of thermodynamics states that none of that energy is destroyed. According to the second law of thermodynamics, some of the energy gets transferred to the bicycle and turns the wheels, while some of it turns into heat. 7. Students drawings should resemble Figure 4 on this page. The spark plug ignition uses electrical energy to convert the chemical energy of gas into mechanical energy, which is also called work. 8. Since cleaning up my room increased the room s order, an increase of disorder elsewhere must be the result. End of chapter Review Answers Using Key Terms 2. A thermometer using the Kelvin scale would have 0 set at absolute zero, while a thermometer using the Celsius scale would have 0 set at the freezing point of water. 3. Warm, moist air rises up as it approaches the mountains. As the air rises, it cools. The cool,

4 dry air continues over the mountain and sinks down the other side toward the desert, creating a downdraft. 4. Metal is a conductor with a low specific heat, so pouring a hot beverage in a metal cup would make the cup hot also. This cup would be unpleasant to hold. A china cup is a better insulator with a higher specific heat, so it will not become hot as rapidly. 5. The dark clothing absorbs energy transferred from the sun by radiation. 6. The amount of entropy in books on a library shelf is lower than the entropy of books that are randomly piled. Understanding Key Ideas 7. b 8. c 9. a 10. d 11. d 12. a 13. d Math Skills = 195 K 1.8( 78) = F = 270 C 1.8( 270) = 454 F

5 25. c = 3,190 J/[(0.400 kg)(308 K 273 K)] = 228 J/kg K 26. c = 1124 J/[(93 g)(1 kg/1000 g)(25 K)] = 480 J/kg K 27. T = (2.4 _ 104 J)/[(897 J/kg K)(0.225 kg)] T = 120 K = 120 C Tf 25 C = 120 C Tf = 145 C