Molar mass
You have a 1 g sample of hydrogen gas and helium gas.
Approximately how many moles and how many molecules do you
have of each sample?
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Conversions are expected
• Values on the temperatures scales (Fahrenheit, Centigrade/Celsius,
and Kelvin) may be readily interconverted. Physics professors will
want values to eventually be in Kelvin because that is the form in
SI units (and Fahrenheit is dumb).
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Temperature scales
Which temperature is greater or smaller: 20 °F, 20 °C, 20
K? Temperatures are ranked from smallest to largest.
A. 20 °F < 20 °C < 20 K
B. 20 °C < 20 °F < 20 K
C. 20 °C < 20 K < 20 °F
D. 20 K < 20 °F < 20 °C
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Temperature scales
Which temperature is greater or smaller: 20 °F, 20 °C, 20
K? Temperatures are ranked from smallest to largest.
A. 20 °F < 20 °C < 20 K
B. 20 °C < 20 °F < 20 K
C. 20 °C < 20 K < 20 °F
D. 20 K < 20 °F < 20 °C
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Temperature scales
Three samples start at the same temperature. The three
samples are then heated by DT = 5 °F, 5 °C and 5 K,
respectively? Which one has the highest final temperature?
DT is ranked from smallest to largest
A. 5 °F < 5 °C = 5 K
B. 5 °C = 5 °F < 5 K
C. 5 °C = 5 K < 5 °F
D. 5 K < 5 °F < 5 °C
Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley
Temperature scales
Three samples start at the same temperature. The three
samples are then heated by DT = 5 °F, 5 °C and 5 K,
respectively? Which one has the highest final temperature?
DT is ranked from smallest to largest
A. 5 °F < 5 °C = 5 K
B. 5 °C = 5 °F < 5 K
C. 5 °C = 5 K < 5 °F
D. 5 K < 5 °F < 5 °C
Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley
Q17.2
A sample of a low-density gas is initially at room
temperature and has pressure p0. The gas is warmed at
constant volume until the pressure is 2p0.
Compared to the initial Celsius temperature of the gas, the
final Celsius temperature is
A. greater by a factor of more than 2.
B. greater by a factor of 2.
C. greater by a factor between 1 and 2.
D. the same.
E. less.
Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley
A17.2
A sample of a low-density gas is initially at room
temperature and has pressure p0. The gas is warmed at
constant volume until the pressure is 2p0.
Compared to the initial Celsius temperature of the gas, the
final Celsius temperature is
A. greater by a factor of more than 2.
B. greater by a factor of 2.
C. greater by a factor between 1 and 2.
D. the same.
E. less.
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Q18.1
A quantity of an ideal gas is contained in a balloon. Initially
the gas temperature is 27°C.
You double the pressure on the balloon and change the
temperature so that the balloon shrinks to one-quarter of its
original volume. What is the new temperature of the gas?
A. 54°C
B. 27°C
C. 13.5°C
D. –123°C
E. –198°C
Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley
A18.1
A quantity of an ideal gas is contained in a balloon. Initially
the gas temperature is 27°C.
You double the pressure on the balloon and change the
temperature so that the balloon shrinks to one-quarter of its
original volume. What is the new temperature of the gas?
A. 54°C
B. 27°C
C. 13.5°C
D. –123°C
E. –198°C
Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley
Q18.2
p
This pV–diagram shows three
possible states of a certain amount
of an ideal gas.
3
2
Which state is at the highest
temperature?
1
A. state #1
B. state #2
O
C. state #3
D. Two of these are tied for highest temperature.
E. All three of these are at the same temperature.
Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley
V
A18.2
p
This pV–diagram shows three
possible states of a certain amount
of an ideal gas.
3
2
Which state is at the highest
temperature?
1
A. state #1
B. state #2
O
C. state #3
D. Two of these are tied for highest temperature.
E. All three of these are at the same temperature.
Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley
V
Car engine
• In automobile engine, a mixture of air and gasoline is
compressed in the cylinders before being ignited. A typical
engine has a compression ratio of 9.00:1. The initial pressure is
1.00 atm and the initial temperature is 27°C. If pressure after
compression is 21.7 atm, find the temperature of the compressed
gas.
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Thermal processes
• You have two identical samples of gas held at P1, V1. One
sample undergoes an isothermal process that halves its volume,
the other undergoes an isobaric process that halves its volume.
• Draw the processes on a PV diagram and find final pressure and
volume Pf and Vf for the two gas samples in terms of P1, V1.
Which gas is at a higher temperature and by what factor?
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PV curves at constant temperature—isotherms
• A single experiment can
measure how pressure changes
as volume changes. This is an
isothermal curve.
• Many isothermal curves
together make a threedimensional phase surface.
• How do you predict from these
graphs what happens to
material in a sealed, rigid
container if temperature is
increased?
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The positions of (s), (l), and (g) are plotted on phase diagrams
• Lines are drawn for freezing, melting, and boiling curves on a pT
axis.
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P, V, and T may all be plotted to form 3-D surfaces
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P, V, and T may all be plotted to form 3-D surfaces II
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