The Behavior of Gases
Three measurable properties of gases:
1. Volume: The amount of space a gas occupies depends on
temperature and air pressure. Gases fill all available space
so the volume of a gas depends on the size of the container.
2. Temperature: the average energy of motion of the particles in
a substance. The faster the particles move, the greater the
temperature.
(Example: At room temperature particles in a gas move at 500
m/s.)
3. Pressure: the force of the push from the particles of a substance
on the walls of the container in which the gas is contained.
(Remember: P = F/area)
Gas particles move from areas of high pressure to areas of low
pressure until equilibrium is reached.
Relationships between the properties of gases:
1. The relationship between pressure and volume is
known as Boyle’s Law.
Boyle’s Law states that, at a constant temperature,
when the pressure of a gas increases the volume
decreases. When the pressure decreases the
volume increases. This relationship is inversely
proportional.
Example: Compressed gases exert greater
pressure such as a CO2 cartridge.
2.
As the temperature of a gas at a constant volume increases so does
the pressure. Heat provides energy to the particles in the gas causing
them to move more rapidly increasing the collisions. The more
collisions that occur the greater the pressure.
As the temperature decreases energy also decreases thus decreasing
the number of collisions of gas particles. The decreased number of
collisions results in decreased pressure. This relationship is directly
proportional.
Example: Tire pressure increases in warm
weather and decreases in cold weather.
3. The relationship between volume and temperature is known as Charles
Law.
Charles Law states that at a constant pressure, when the temperature of a
gas increases its volume also increases. When the temperature of a gas
decreases, its volume decreases.
This relationship is directly proportional. As the temperature increases, the
gas particles increase motion. The volume of a gas must increase to keep
rate of collisions constant thus, keeping the pressure constant. If the volume
of a container of gas can change, the total force from the collisions results in
the gas taking up more space.
Example: Hot air balloon – as air is heated it fills up the balloon.
Law
Volume
Temperature
Pressure
Relationship
Boyle’s
Increase
Constant
Decrease
Inverse
Boyle’s
Decrease
Constant
Increase
Inverse
Charles
Increase
Increase
Constant
Directly
Charles
Decrease
Decrease
Constant
Directly
Pressure and
Temperature
Constant
Increase
Increase
Directly
Pressure &
Temperature
Constant
Decrease
Decrease
Directly