Kinetic Theory is simply the application of Newton's Laws to ideal gases. You start with one atom of ideal gas in a box and determine the pressure associated with that atom. Then you add more atoms and sum (or average) over all the atoms to see what you get.

Results include:

1. Pressure is associated with collisions of the particles with the walls. When a particle hits a wall the wall exerts a force on the particle to change the particle's momentum (only the direction changes, not the magnitude). The particle exerts an equal-and-opposite force back on the wall. Dividing the total force from all the particles by the wall area gives the pressure.

Increasing temperature means the particles move faster so the pressure goes up - there are more collisions and the collisions involve a larger average force.
For a fixed volume and temperature, adding more particles increases pressure because there are more collisions with the walls of the container.

What is the average velocity of the ideal gas particles?

2. The average velocity is zero, because, on average, the velocity of particles going in one direction is cancelled by the velocity of particles going in the opposite direction. You might think it would make sense to talk about the average speed of the particles, but when you do the analysis you find that the thing that really matters is the rms-speed (rms stands for root mean square).

3. The really fundamental result that comes out of kinetic theory is that temperature is a direct measure of the average kinetic energy of the particles of ideal gas.

Compare the kinetic theory result:

PV

=

2N 3

Kav

to the ideal gas law

PV = NkT

This tells us that the average translational kinetic energy of the molecules is:

Kav

=

3 2

kT

Here we have a fundamental connection between temperature and the average translational kinetic energy of the atoms - they are directly proportional to one another. Temperature is a measure of the average kinetic energy of the atoms.