Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Solving Problems: A Chemistry Handbook
Chemistry: Matter and Change
117
States of Matter
States of Matter
SOLVING PROBLEMS:
A CHEMISTRY HANDBOOK
CHAPTER
12
12.1 Gases
In the late 1800s, two scientists, Ludwig Boltzmann and James
Maxwell, independently proposed a model to explain the properties
of gases in terms of particles in motion. This model is now known as
the kinetic-molecular theory. The model makes the following
assumptions about the size, motion, and energy of gas particles.
• Particle size The particles in a gas are separated from one
another by empty space. The volume of the empty space is much
greater than the volume of the gas particles themselves. Because
gas particles are so far apart, there are no significant attractive or
repulsive forces between them.
• Particle motion Gas particles are in constant, random motion.
Until they bump into something (another particle or the side of a
container), particles move in a straight line. When gas particles
do collide with something, the collision is said to be elastic. An
elastic collision is one in which no kinetic energy is lost.
Although kinetic energy may be transferred from one particle to
another, the total amount of kinetic energy of the two particles
does not change.
• Particle energy Mass and velocity determine the kinetic energy
of a particle, as represented in the equation below.
KE ϭ ᎏ
1
2
ᎏ mv 2
KE ϭ kinetic energy
m ϭ mass of the particle
v ϭ velocity of the particle
The velocity of a particle includes both its speed and its direction.
Each particle in a sample containing only one gas will have the same
mass but not the same velocity. Thus, all the particles in a sample of
gas do not have the same kinetic energy. Temperature is a measure
of the average kinetic energy of the particles in a sample of matter.
At a given temperature, all gases have the same average kinetic
energy.
Solving Problems: A Chemistry Handbook
Chemistry: Matter and Change
117
States of Matter
States of Matter
SOLVING PROBLEMS:
A CHEMISTRY HANDBOOK
CHAPTER
12
12.1 Gases
In the late 1800s, two scientists, Ludwig Boltzmann and James
Maxwell, independently proposed a model to explain the properties
of gases in terms of particles in motion. This model is now known as
the kinetic-molecular theory. The model makes the following
assumptions about the size, motion, and energy of gas particles.
• Particle size The particles in a gas are separated from one
another by empty space. The volume of the empty space is much
greater than the volume of the gas particles themselves. Because
gas particles are so far apart, there are no significant attractive or
repulsive forces between them.
• Particle motion Gas particles are in constant, random motion.
Until they bump into something (another particle or the side of a
container), particles move in a straight line. When gas particles
do collide with something, the collision is said to be elastic. An
elastic collision is one in which no kinetic energy is lost.
Although kinetic energy may be transferred from one particle to
another, the total amount of kinetic energy of the two particles
does not change.
• Particle energy Mass and velocity determine the kinetic energy
of a particle, as represented in the equation below.
KE ϭ ᎏ
1
2
ᎏ mv 2
KE ϭ kinetic energy
m ϭ mass of the particle
v ϭ velocity of the particle
The velocity of a particle includes both its speed and its direction.
Each particle in a sample containing only one gas will have the same
mass but not the same velocity. Thus, all the particles in a sample of
gas do not have the same kinetic energy. Temperature is a measure
of the average kinetic energy of the particles in a sample of matter.
At a given temperature, all gases have the same average kinetic
energy.