Questions

  1. Running hot water over the metal lid of a glass jar makes it easier to open the jar. Why?
  2. When a mercury-in-glass thermometer is heated, its mercury column goes down briefly before rising. Why?
  3. Is it meaningful to say that an object at a temperature of 200° C is twice as hot as one at 100° C
  4. Why do tables of densities always include the temperature for which the listed values hold? What would be true of the densities of most solids and liquids at a temperature higher than the quoted one?
  5. When a person drinks a soda through a straw, where does the force come from that causes the soda to move upward?
  6. A jar is filled to the top with water, and a piece of cardboard is slid over the opening so that there is only water in the jar. If the jar is turned over, will the cardboard fall off? What will happen if there is any air in the jar?
  7. some water is boiled briefly in an open metal can. The can is then sealed while still hot. What does the can collapse when it cools?
  8. A U-shaped tube contains water and an unknown liquid separated by mercury, as in Fig. 4-39. How does the density of the liquid compare with the density of water? How do the pressures at A and B compare?
  9. The tree containers shown in Fig. 4-40 are filled with water to the same height. Compare the pressure at the bottoms of the containers.
  10. A highway bridge in Sweden carries the Gota Canal over a highway. What, if anything, happens to the load on the bridge when a boat passes across it in the canal?
  11. As Table 4-2 shows, ice has a lower density than water, which is why ice floats. What will happen when an ice cube floating in a glass of water filled to the brim begins to melt?
  12. An ice cube with an air bubble inside it is floating in a glass of water. Compare what happens to the water level in the glass when the ice melts with what would happen if the cube had no bubble in it.
  13. An aluminum canoe is floating in a swimming pool. After a while it begins to lead and sinks to the bottom of the pool. What, if anything happens to the water level in the pool?
  14. Suppose the pressure in a liquid did not increase with depth. Would anything float in such a liquid?
  15. When water is boiled in a pan, the bubbles of steam increase in size as they rise through the water. Why?
  16. Gas molecules have speeds comparable with those of rifle bullets, yet it is observed that a gas with a strong odor (ammonia, for instance) takes a few minutes to diffuse through a room. Why?
  17. At absolute zero, a sample of an ideal gas would have zero volume. Why would this not be true of an actual gas at absolute zero?
  18. The pressure on a sample of hydrogen is doubled while its temperature is kept unchanged. What happens to the average speed of the hydrogen molecules?
  19. When they are close together, molecules attract one another slightly. As a result of this attraction, are gas pressures higher or lower than expected from the ideal gas law?
  20. Temperatures in both the Celsius and Fahrenheit scales can be negative. Why is an negative temperature impossible on the absolute scale?
  21. How can the conclusion of kinetic theory that molecular motion occurs in solids be reconciled with the observation that solids have definite shapes and volumes?
  22. You can safely put your hand inside a hot oven for a short time but even a momentary contact with the metal walls of the oven will cause a burn. Explain.
  23. Why is a piece of ice at 0° C more effective in cooling a drink than the same mass of cold water at 0° C?
  24. Would it be more efficient to warm you bed on a cold night with a hot water bottle that contain 1 kg of water at 50° C or a 1-kg gold bar at 50° C?
  25. Canteens often have cloth coverings. On a hot day, what is the advantage to keeping to cloth around a canteen wet?
  26. Why does evaporation cool a liquid?
  27. Give as many methods as you can think of that will increase the rate of evaporation of a liquid sample. Explain why each method will have this effect.
  28. If you wish to speed up the rate at which potatoes are cooking in a pan of boiling water, would it be better to turn up the gas flame or use a pressure cooker?
  29. Why are both a hot and a cold reservoir needed for a heat engine to operate?
  30. The ocean contain an immense amount of heat energy. Why can a submarine not make use of this energy for propulsion?
  31. Is it correct to say that a refrigerator "produces cold"? If not, why not?
  32. A person tries to cool a kitchen by switching on an electric fan and closing the kitchen door and window. What will happen?
  33. In another attempt to cool the kitchen, the person leaves the refrigerator door open, again with the kitchen door and windows closed. Now what will happen?
  34. When salt is dissolved in water, do you think the entropy of the system of salt and water increase or decreases? Why?