Chapter 7
Exercises
1. The varying conductivity of different objects
can give different temperature sensations to objects with a common temperature.
4. No. Heat flows from your hand through the metal
nail to the ice. The loss of heat in your hand provides the sensation of
cold.
8. Fiberglass is used because of its ability to
trap air between the fibers. The air pockets dramatically increase its ability
to insulate.
12. Place the ice block on top of the object.
13. The majority of the heat is transferred from
the paper to the water. The boiling point of water (212º F) is well
below the ignition point of water ( 451º F). TRIVIA: Who wrote Fahrenheit
451, and what is it about?
15. Air is a poor conductor. The air will not transfer
the high temperature of the oven very quickly. the metal, on the other hand
(no pun intended), is a good conductor and will transfer the heat very quickly.
18. The smoke, being warmer than the surrounding air, will rise. As it rises it expands and cools. Eventually it reaches a point where its density and temperature match the air around it, thus it begins to settle and spread out.
20. The hydrogen molecules will move faster. Same
temperature means both hydrogen and oxygen have the same KE. Recall KE =
1/2mv^2 and since hydrogen molecules are smaller than oxygen molecules they
must move faster in order to give the same KE.
22. No. As air expands it cools. Expanding a volume
of air will cause a decrease in temperature.
24. The mixture expands when it exits the nozzle, and therefore cools enough to form ice crystals.
28. No. If a good absorber is only a good absorber,
then its temperature will climb higher than its surroundings. Also, if a
poor absorber were a good emitter, its temperature would fall below the
temperature of its surroundings.
32. To prevent too much solar energy entering the
greenhouse and thus overheating the inside.
33. Wear the plastic coat on the outside.
34. If more terrestrial radiation could escape the earth's temperature would decrease. If less terrestrial radiation could escape the earth's temperature would increase.