Download WBL6_Lecture_Ch10-2djgx21

Lecture Outlines
Chapter 10
College Physics, 6th Edition
Wilson / Buffa / Lou
© 2007 Pearson Prentice Hall
This work is protected by United States copyright laws and is provided solely for
the use of instructors in teaching their courses and assessing student learning.
Dissemination or sale of any part of this work (including on the World Wide Web)
will destroy the integrity of the work and is not permitted. The work and materials
from it should never be made available to students except by instructors using
the accompanying text in their classes. All recipients of this work are expected to
abide by these restrictions and to honor the intended pedagogical purposes and
the needs of other instructors who rely on these materials.
Chapter 10
Temperature and Kinetic
Theory
Units of Chapter 10
Temperature and Heat
The Celsius and Fahrenheit Temperature Scales
Gas Laws, Absolute Temperature, and the
Kelvin Temperature Scale
Thermal Expansion
The Kinetic Theory of Gases
Kinetic Theory, Diatomic Gases, and the
Equipartition Theorem
10.1 Temperature and Heat
Temperature is a measure of relative hotness
or coldness.
Heat is the net energy transferred from one
object to another due to a temperature
difference.
This energy may contribute to the total internal
energy of the object, or it may do work, or both.
10.1
Temperature
and Heat
10.1 Temperature and Heat
A higher temperature does not necessarily
mean that one object has more internal energy
than another; the size of the object matters as
well.
When heat is transferred from one object to
another, they are said to be in thermal contact.
Two objects in thermal contact without heat
transfer are in thermal equilibrium.
10.2 The Celsius and Fahrenheit
Temperature Scales
A thermometer is used to measure
temperature; it must take advantage of some
property that depends on temperature. A
common one is thermal expansion.
10.2 The Celsius and Fahrenheit
Temperature Scales
In everyday use, temperature is
measured in the Fahrenheit or
Celsius scale.
To convert from one to the
other:
10.3 Gas Laws, Absolute Temperature,
and the Kelvin Temperature Scale
When the temperature of an ideal gas is held
constant,
When the pressure is held constant,
10.3 Gas Laws, Absolute Temperature,
and the Kelvin Temperature Scale
Combining gives the ideal gas law:
or
with Boltzmann’s constant:
N is the total number of molecules in the gas.
10.3 Gas Laws, Absolute Temperature,
and the Kelvin Temperature Scale
The ideal gas law can also be written
where n is the number of moles of gas and R
is the universal gas constant:
A mole of a substance contains Avogadro’s
number of molecules:
10.3 Gas Laws, Absolute Temperature,
and the Kelvin Temperature Scale
A constant-volume gas thermometer is useful
because the temperature is directly proportional
to the pressure. If P-T curves are plotted for
different gases, they converge at zero pressure.
10.3 Gas Laws, Absolute Temperature,
and the Kelvin Temperature Scale
The temperature at which this occurs is called
absolute zero—no lower temperature is
possible.
The Kelvin temperature scale has the same
increments as the Celsius scale, but has its
zero at absolute zero.
10.3 Gas Laws, Absolute Temperature,
and the Kelvin Temperature Scale
The three temperature
scales are shown here. In
physics calculations, the
Kelvin temperature scale is
used.
The Kelvin scale is also
called the absolute scale, as
the Kelvin temperature is
proportional to the internal
energy.
10.4 Thermal Expansion
Most materials expand when heated. For small
changes in temperature, the change in length is
proportional to the change in temperature.
10.4 Thermal Expansion
The changes in area and in volume can be
derived from the change in length.
10.4 Thermal Expansion
10.4 Thermal Expansion
Water behaves nonlinearly near its freezing
point—it actually expands as it cools. This is
why ice floats, and why frozen containers may
burst.
10.5 Kinetic Theory of Gases
According to the kinetic
theory of gases, pressure
is due to elastic collisions
of molecules with
container walls.
10.5 Kinetic Theory of Gases
Using the kinetic theory, it can be shown that
The mass and speed are those of an individual
molecule.
The molecular kinetic energy can be related
to the temperature:
10.5 Kinetic Theory of Gases
The internal energy of a monatomic gas is due
to the kinetic energy of its atoms, and is
therefore related to its temperature.
10.5 Kinetic Theory of Gases
The kinetic theory of gases also helps us
understand diffusion as a result of the motion
of molecules.
10.6 Kinetic Theory, Diatomic Gases,
and the Equipartition Theorem
The atoms in a monatomic
gas have only translational
equilibrium to contribute to
the internal energy. A
diatomic molecule can also
rotate around two distinct
axes (x and y).
10.6 Kinetic Theory, Diatomic Gases,
and the Equipartition Theorem
The equipartition theorem tells us what the
contribution of the rotational states is to the
internal energy.
A diatomic molecule has 5 degrees of
freedom—translation in x, y, or z, rotation
around x, and rotation around y.
10.6 Kinetic Theory, Diatomic Gases,
and the Equipartition Theorem
The predicted internal energy of a diatomic
gas is then:
Summary of Chapter 10
Celsius–Fahrenheit conversions:
Heat is the energy transferred from one
object to another due to temperature
difference.
Summary of Chapter 10
Ideal gas law:
Absolute zero is –273.15°C.
Celsius–Kelvin conversion:
Summary of Chapter 10
Thermal expansion:
Results of kinetic theory of
gases:
(monatomic gas)
(diatomic gas)