Which has a specific volume?
Which has a specific shape?
Compressibility – how much the volume of
matter decreases under pressure
A gas can be squeezed into a small space
See the all the space
between the gas
particles? The particles
can be squeezed closer
together under pressure
Pressure is the force the gas molecules exert
on the container as they collide with it
Four variables to describe a gas:
Pressure (P): measured in kilopascals (kPa)
Volume (V): measured in liters (L)
Temperature (T): measured in kelvins (K)
Amount (n): measured in number of moles
When you pump air into a container, you
increase the amount of gas inside the tire,
which increases the number of collisions between
which increases the pressure
Relationship is direct:
If you double the amount of gas, the pressure
Fewer gas particles,
More gas particles, higher
In a sealed container, gases move from an
area of high pressure to low pressure
If the volume of a container is reduced, the
pressure will increase
If the volume of a container is increased, the
pressure will decrease
Relationship is inverse
If the volume is doubled, the pressure will
decrease by half
If the temperature is increased, the particles
will move faster,
Which causes more collisions between particles
Which increases the pressure
Increasing the temperature causes the
pressure to increase
Decreasing the temperature will cause the pressure to
Relationship is direct
As the temperature is doubled, the pressure is doubled
As the temperature is decreased by half, the pressure will
decrease by half
1. Why is a gas easy to compress?
2. List three factors that can affect gas pressure.
3. Why does a collision with an air bag cause less damage
than a collision with a steering wheel? (extra help)
4. How does a decrease in temperature affect the pressure
of a contained gas?
5. If the temperature is constant, what change in volume
would cause the pressure of an enclosed gas to be
reduced to one quarter of its original volume?
6. What happens to particle motion as the temperature
increases? What if it decreases?
7. Write a paragraph explaining how the compressed gas in
an aerosol can force paint out of the can. Describe how
the gas pressure inside the can changes as the paint is
sprayed, and identify the variable that causes this
change. Refer to figure 14.5 in the text.