Chapter 12
Thermal
Properties of
Matter
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PowerPoint® Lectures for
College Physics: A Strategic Approach, Second Edition
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Slide 12-3
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Slide 12-4
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Slide 12-5
Phases of Matter
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Slide 12-16
Atomic mass unit (either u or amu)
1 u = 1.66 X 10^-27 kg
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Checking Understanding
What is the mass, in u, of a molecule of carbon dioxide, CO2?
A. 
B. 
C. 
D. 
E. 
12
24
32
36
44
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Slide 12-12
Answer
What is the mass, in u, of a molecule of carbon dioxide, CO2?
A. 
B. 
C. 
D. 
E. 
12
24
32
36
44
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Slide 12-13
Checking Understanding
Rank the following in terms of the number of moles, from greatest
number of moles to least:
1.
2.
3.
4.
5.
20 g of He (A = 4)
60 g of Ne (A = 20)
120 g of O2 (atomic oxygen, O, has A = 16)
160 g of Ar (A = 40)
200 g of Pb (A = 207)
A. 
B. 
C. 
D. 
5>4>3>2>1
5>4>2>3>1
3>1>4>2>5
1>4>3>2>5
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Slide 12-14
Answer
Rank the following in terms of the number of moles, from greatest
number of moles to least:
1.
2.
3.
4.
5.
20 g of He (A = 4)
60 g of Ne (A = 20)
120 g of O2 (atomic oxygen, O, has A = 16)
160 g of Ar (A = 40)
200 g of Pb (A = 207)
A. 
B. 
C. 
D. 
5>4>3>2>1
5>4>2>3>1
3>1>4>2>5
1>4>3>2>5
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Slide 12-15
Speed and Kinetic Energy of Gas Molecules
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Slide 12-17
Checking Understanding
An object moving faster than the earth’s escape velocity (about
11 km/s) has enough energy to escape the pull of the earth’s
gravity. 11 km/s is pretty speedy, but gas atoms move at high
speeds. Which one of the following gas molecules would be most
likely to be moving at a speed high enough to escape the earth’s
atmosphere?
A. 
B. 
C. 
D. 
E. 
Carbon dioxide
Oxygen
Nitrogen
Water vapor
Hydrogen
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Slide 12-19
Answer
An object moving faster than the earth’s escape velocity (about
11 km/s) has enough energy to escape the pull of the earth’s
gravity. 11 km/s is pretty speedy, but gas atoms move at high
speeds. Which one of the following gas molecules would be most
likely to be moving at a speed high enough to escape the earth’s
atmosphere?
A. 
B. 
C. 
D. 
E. 
Carbon dioxide
Oxygen
Nitrogen
Water vapor
Hydrogen
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Slide 12-20
Example Problem
What are the rms speeds of a nitrogen molecule (mass
4.5 × 10-26 kg) at the following temperatures?
A.  Room temperature of 68ºF (20ºC)
B.  The coldest temperature ever observed on earth,
-129ºF (-89ºC)
C.  Polar night on Mars, -133ºC
D.  The coldest temperature achieved in the laboratory,
0.5 nK
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Slide 12-18
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The Definition of Pressure
1 pascal = 1 Pa = 1 N/m2
1 atmosphere = 101,300 Pa
= 101.3 kPa
= 14.7 psi
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Demo time
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The Ideal Gas Law
Changing the temperature, volume or number of particles
changes the pressure of the gas. We can understand this using
our model of the ideal gas.
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Slide 12-28
The Ideal Gas Law
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Slide 12-21
Ideal Gas Law for a Fixed Amount of Gas
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Slide 12-22
Reading Quiz
2.  A sample of nitrogen gas is in a sealed container with a
constant volume. Heat is added to the gas. The pressure
A. 
B. 
C. 
D. 
increases
stays the same
decreases
can’t be determined with the information given
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Slide 12-8
Answer
2.  A sample of nitrogen gas is in a sealed container with a
constant volume. Heat is added to the gas. The pressure
A. 
B. 
C. 
D. 
increases
stays the same
decreases
can’t be determined with the information given
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Slide 12-9