1. Pressure of a gas

2. Kinetic theory of gases
The particles of a gas are in constant rapid random motion
The forces between the particles is negligible
The particles collide with each other and with the walls of the container.
All the collisions are perfectly elastic. (no kinetic energy is lost)
The time for the collisions is negligible compared to the time between collisions
The volume of the particles is negligible compared to the volume of the gas

3. The pressure of a gas is the force from all the particles
hitting 1 m2 of the walls of the container.
Force
Pressure =
_____________
area

4. We can’t see the particles, so what is the evidence?
Brownian motion
Dust mites seem to dance around in the air
Albert Einstein explained it. He said that the
random movement of the dust mites (or smoke
particles ) which are large and we can see because of the light reflected from them,
is due to very much smaller particles, which we can’t see, jostling them about.

6. What happens if we raise the temperature of a gas but keep the volume the same

7. Because the temperature increases the average kinetic energy of the particles,
they hit the walls of the container harder and more often and so the pressure increases
Draw a graph of pressure and temperature (⁰C)

9. The experimenter says ‘it makes the molecules contract’
What is wrong with this statement?