Page 256 - Schaum's Outline of Theory and Problems of Applied Physics

CHAP. 20] KINETIC THEORY OF MATTER 241

Multiple-Choice Questions

20.1. Molecular motion in a gas stops
(a) at absolute zero
(b) when the gas becomes a liquid
(c) when the gas becomes a solid
(d) when the pressure on it exceeds a certain value

20.2. At a given temperature
(a) the molecules in a gas all have the same average velocity
(b) the molecules in a gas all have the same average energy
(c) light gas molecules have lower average energies than heavy gas molecules
(d) heavy gas molecules have lower average energies than light gas molecules

20.3. The temperature of a gas sample in a container of fixed volume is raised. The gas exerts a higher pressure on the
walls of its container because its molecules

(a) lose more PE when they strike the walls.
(b) lose more KE when they strike the walls
(c) are in contact with the walls for a shorter time
(d) have higher average velocities and strike the walls more often
20.4. The volume of a gas sample is increased while its temperature is held constant. The gas exerts a lower pressure on
the walls of its container partly because its molecules strike the walls
(a) less often (c) with less energy
(b) with lower velocities (d) with less force

20.5. When evaporation occurs, the liquid that remains is cooler because
(a) the pressure on the liquid decreases
(b) the volume of the liquid decreases
(c) the slowest molecules remain behind
(d) the fastest molecules remain behind

20.6. When a volume of air is heated,
(a) it can hold less water vapor
(b) it can hold more water vapor
(c) the amount of water vapor it can hold does not change
(d) its relative humidity increases

20.7. Cooling saturated air causes
(a) its relative humidity to decrease
(b) its relative humidity to increase
(c) its ability to take up water vapor to increase
(d) some of its water content to condense out

20.8. Which one or more of the following quantities are the same for both a mole of oxygen molecules and a mole of
nitrogen molecules at the same temperature and pressure?
(a) the number of molecules present
(b) the average velocities of the molecules
(c) the volume of the gas
(d) the density of the gas