AP Chemistry
Unit 5 – States of Matter
Lesson 4 – Kinetic/Molecular Theory
Book Section: 10.7
Kinetic-Molecular Theory
• This is a model that
aids in our
understanding of what
happens to gas
particles as
environmental
conditions change.
• This determines what
is an ideal gas.
Main Tenets of Kinetic-Molecular
Theory
• The combined volume of all molecules of
the gas is negligible relative to the total
volume in which the gas is contained.
• In other words, the volume of the gas
molecules themselves doesn’t matter.
Main Tenets of Kinetic-Molecular
Theory
• Attractive and
repulsive forces
between gas
molecules are
negligible.
Main Tenets of Kinetic-Molecular
Theory
• Energy can be
transferred between
molecules during
collisions, but the
average kinetic energy
of the molecules does
not change with time,
as long as the
temperature of the gas
remains constant.
Main Tenets of Kinetic-Molecular
Theory
• The average kinetic
energy of the
molecules is
proportional to the
absolute
temperature.
1994 MC #45
•
A sample of an ideal gas is cooled from
50.0 ºC to 25.0 ºC in a sealed container of
constant volume. Which of the following values
for the gas will decrease?
I. The average molecular mass of the gas
II. The average distance between the molecules
III. The average speed of the molecules
A) I only
B) II only
C) III only
D) I and III
E) II and III
1994 MC #45
•
A sample of an ideal gas is cooled from
50.0 ºC to 25.0 ºC in a sealed container of constant
volume. Which of the following values for the gas will
decrease?
I. The average molecular mass of the gas
II. The average distance between the molecules
III. The average speed of the molecules
A) I only
B) II only
C) III only – 44% correct, medium
D) I and III
E) II and III
1999 MC #22
•
A)
B)
C)
D)
E)
A hot air balloon, shown above, rises.
Which of the following is the best
explanation for this observation?
The pressure on the inside of the walls
of the balloon increases with increasing
temperature.
The difference in temperature between
the air inside and outside the balloon
produces convection currents.
The cooler air outside the balloon
pushes in on the walls of the balloon.
The rate of diffusion of cooler air is less
than that of warmer air.
The air density inside the balloon is less
than that of the surrounding air.
1999 MC #23
•
A)
B)
C)
D)
E)
A hot air balloon, shown above, rises.
Which of the following is the best
explanation for this observation?
The pressure on the inside of the walls
of the balloon increases with increasing
temperature.
The difference in temperature between
the air inside and outside the balloon
produces convection currents.
The cooler air outside the balloon
pushes in on the walls of the balloon.
The rate of diffusion of cooler air is less
than that of warmer air.
The air density inside the balloon is
less than that of the surrounding air.
– 68% correct, easy
1999 MC #44
•
A)
B)
C)
D)
E)
A rigid metal tank contains oxygen gas. Which of the
following applies to the gas in the tank when additional
oxygen is added at constant temperature?
The volume of the gas increases.
The pressure of the gas decreases.
The average speed of the gas molecules remains the same.
The total number of gas molecules remains the same.
The average distance between the gas molecules increases.
1999 MC #44
•
A)
B)
C)
D)
E)
A rigid metal tank contains oxygen gas. Which of the
following applies to the gas in the tank when additional
oxygen is added at constant temperature?
The volume of the gas increases.
The pressure of the gas decreases.
The average speed of the gas molecules remains the
same. – 54% correct, medium
The total number of gas molecules remains the same.
The average distance between the gas molecules increases.
Homework: 10.72, 10.74
• Next week:
– Monday: Volume-Temperature Behavior of Gases Lab
– Tuesday: Graham’s Law of Effusion (10.8)
– Wednesday: Volume-Temperature Behavior of Gases
Lab
– Thursday: Van der Waals Equation (10.9)
– Friday: Gas Stoichiometry (10.5)
• Due Dates:
–
–
–
–
Volume-Temperature Behavior of Gases: 11/30
States of Matter Exam: Monday, 12/6
Molar Mass of Condensable Vapor: 12/8
Problem Set 4: 12/10