Chapter 19 - 19 Temperature CHAPTER OUTLINE 19.1 19.2 19.3...

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19 CHAPTER OUTLINE 19.1 Temperature and the Zeroth Law of Thermodynamics 19.2 Thermometers and the Celsius Temperature Scale 19.3 The Constant-Volume Gas Thermometer and the Absolute Temperature Scale 19.4 Thermal Expansion of Solids and Liquids 19.5 Macroscopic Description of an Ideal Gas Temperature ANSWERS TO QUESTIONS Q19.1 Two objects in thermal equilibrium need not be in contact. Consider the two objects that are in thermal equilibrium in Figure 19.1(c). The act of separating them by a small distance does not affect how the molecules are moving inside either object, so they will still be in thermal equilibrium. Q19.2 The copper’s temperature drops and the water temperature rises until both temperatures are the same. Then the metal and the water are in thermal equilibrium. Q19.3 The astronaut is referring to the temperature of the lunar surface, specifically a 400°F difference. A thermometer would register the temperature of the thermometer liquid. Since there is no atmosphere in the moon, the thermometer will not read a realistic temperature unless it is placed into the lunar soil. Q19.4 Rubber contracts when it is warmed. Q19.5 Thermal expansion of the glass bulb occurs first, since the wall of the bulb is in direct contact with the hot water. Then the mercury heats up, and it expands. Q19.6 If the amalgam had a larger coefficient of expansion than your tooth, it would expand more than the cavity in your tooth when you take a sip of your ever-beloved coffee, resulting in a broken or cracked tooth! As you ice down your now excruciatingly painful broken tooth, the amalgam would contract more than the cavity in your tooth and fall out, leaving the nerve roots exposed. Isn’t it nice that your dentist knows thermodynamics? Q19.7 The measurements made with the heated steel tape will be too short—but only by a factor of 51 0 5 × of the measured length. Q19.8 (a) One mole of H 2 has a mass of 2.016 0 g. (b) One mole of He has a mass of 4.002 6 g. (c) One mole of CO has a mass of 28.010 g. Q19.9 The ideal gas law, PV nRT = predicts zero volume at absolute zero. This is incorrect because the ideal gas law cannot work all the way down to or below the temperature at which gas turns to liquid, or in the case of CO 2 , a solid. 549
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550 Temperature Q19.10 Call the process isobaric cooling or isobaric contraction. The rubber wall is easy to stretch. The air inside is nearly at atmospheric pressure originally and stays at atmospheric pressure as the wall moves in, just maintaining equality of pressure outside and inside. The air is nearly an ideal gas to start with, but PV nRT = soon fails. Volume will drop by a larger factor than temperature as the water vapor liquefies and then freezes, as the carbon dioxide turns to snow, as the argon turns to slush, and as the oxygen liquefies. From the outside, you see contraction to a small fraction of the original volume.
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Chapter 19 - 19 Temperature CHAPTER OUTLINE 19.1 19.2 19.3...

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