CHAPTER 10 Quick Quizzes 1.(b). The glass surrounding the mercury expands before the mercury does, causing the level of the mercury to drop slightly. The mercury rises after it begins to get warmer and approach the temperature of the hot water, because its coefficient of expansion is greater than that for glass. 2.(c). Gasoline has the highest coefficient of expansion. 3. (c). A cavity in a material expands in exactly the same way as if the cavity were filled with material. Thus, both spheres will expand by the same amount. 4.(a) On a cold day, the trapped air in the bubbles would be reduced in pressure, according to the ideal gas law. Thus, the volume of the bubbles may be smaller than on a hot day, and the material would not be as effective in cushioning the package contents. 5.(a). It expands. Imagine the balloon rising into air at uniform temperature. The air cannot be uniform in pressure because the lower layers support the weight of all the air above them. The rubber in a typical balloon stretches or contracts until interior and exterior pressures are nearly equal. So as the balloon rises, it expands; this can be considered as constant temperature expansion with Vincreasing as Pdecreases by the same factor in PVnRT=. If the rubber wall is strong enough, the buoyant force will eventually match the total weight of the balloon and helium so the balloon will stop rising. It is more likely that the rubber will stretch and rupture, releasing the helium, which in turn will escape from the Earth’s atmosphere. 6.(b). Helium, because it has the lower molar mass. 321
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