Chapter 19 QQ

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QUICK QUIZ 19.1
(end of section 19.1)
In a kitchen experiment, you empty a tray of ice cubes into a bowl of water. After
an hour or so, when the mixture has come to thermal equilibrium, you notice a little
more water in the bowl than you started with and fewer ice cubes in the bowl than
you started with. One can say that a) the temperature of the water is slightly higher
than the remaining ice cubes, b) the temperature of the water is slightly lower than
the remaining ice cubes, c) the temperature of the water is the same as the
temperature of the remaining ice cubes, or d) the temperature of the water or the ice
cubes depends on the exact mass of water and ice cubes in the bowl.
QUICK QUIZ 19.1 ANSWER
(c). Thermal equilibrium means that the temperature of the
water and the ice cubes must be the same. Temperature is the
property of an object that defines whether it will be in thermal
equilibrium with another object. It does not matter what the
composition, state, or phase of the objects are. By the zeroth
law, if they have the same temperature, they must be in thermal
equilibrium and visa versa.
QUICK QUIZ 19.2
(end of section 19.3)
The three curves of the
figure at right indicate that,
for each gas, a) the
pressure of the gas is
proportional to the
temperature of the gas, b)
the pressure of the gas is
linearly dependent on the
temperature of the gas, c)
both a and b, or d) neither a
nor b.
QUICK QUIZ 19.2 ANSWER
(b). Although only two data points are shown for each gas, the
lines are justified in the text of Section 19.3 by the statement
that experiments show a linear relationship between pressure
and temperature. However, linear does not necessarily mean
proportional. If pressure were proportional to the temperature,
this would imply that a doubling of the temperature would be
accompanied by a doubling of the pressure. An examination
of pressures that correspond to temperatures between 100 and
200°C indicates that this is clearly not the case. For a graph to
be proportional it must be linear and have a y intercept that is
zero. This criteria is met only for the Kelvin temperature scale
where zero temperature is associated with zero pressure.
QUICK QUIZ 19.3
(end of section 19.4)
You have an option of using one of four differently shaped mercury
thermometers to measure temperature changes in a very sensitive
experiment. To obtain the highest sensitivity, that is the biggest
change in height of the mercury column for a given change in
temperature, you should use thermometer a) a, b) b, c) c, d), d or e) a,
b, c, or d, each will work equally well.
QUICK QUIZ 19.3 ANSWER
(a). From Equation 19.6, DV = bViDT, a large
volume change will be associated with a large initial
total volume (volume of bulb plus column). For this
reason, you would not choose thermometers c or d
because of their much smaller total volumes. In
addition, you would like to have a narrow column so
that a given change in volume is associated with a
large change in height. Thermometer “a” best
satisfies both of the desired criteria.
QUICK QUIZ 19.4
(end of section 19.4)
You are designing a railroad and must determine an appropriate gap spacing
between adjoining rails to allow for the linear expansion of the rails during hot
weather. The rails are made from an alloy of steel with a linear expansion
coefficient equal to 10 x 10-6 (°C-1) and are initially 10 meters long. For a
maximum temperature increase of 40°C, Equation 19.4, DL = aLDT , yields a
change in length, DL = (10 x 10-6 (°C-1))(10 m)(40°C) = 0.004 m = 4 mm. So that
the rails just touch with a 40°C temperature increase, the gap spacing between
adjoining rails should be a) 1 mm, b) 2 mm, c) 4 mm, d) 8 mm, or e) 16 mm.
QUICK QUIZ 19.4 ANSWER
(c). The final length of each rail will be Li + DL. This means that
each end of a rail will increase in length by DL/2. In the gap, each
adjoining rail will move toward one another by DL/2 which means
that the gap should be equal to just DL.
QUICK QUIZ 19.5
(end of section 19.5)
Using the cylinder shown at right, you
measure the initial pressure, volume and
temperature of the ideal gas in the
container. You then push down on the
piston until the pressure increases by a
factor of two. If you then measure the
temperature of the gas, you will notice that
a) it has also increased by a factor of two,
b) it has remained constant, c) it has
decreased by a factor of two, or d) it is
impossible to determine from the given
information.
QUICK QUIZ 19.5 ANSWER
(d). The ideal gas law, PV = nRT, determines the state of
the gas in terms of the variables, P, V, n, and T. Since no
gas escapes, the number of moles will remain constant so
that,
PV
1 1  nRT1 and PV
2 2  nRT2 , and
T2 PV
V2
2 2

2 .
T1 PV
V1
1 1
Without knowing how the volume changes, it is impossible
to determine the change in temperature. For example, the
volume could be reduced by a factor of two which would
keep the temperature constant. However, it would also be
possible for the volume to be reduced by a factor less than
or more than two which would be accompanied by an
increase or decrease in temperature.
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