Ideal gas law $PV=N k T$ :  gas consists of N particle at tempearture T in a container (volume V) with pressure P.
And temperature $T$ is proportional to $V_{avg}^2$ where $V_{avg}$ is the average velocity for all the particles.

This java applet shows a microscopic model for an ideal gas. The pressure that a gas exerts on the walls of its container is a consequence of the collisions of the gas molecules with the walls.
In this model:
1. The molecules obey Newton's law of motion.

2. The molecules move in all direction with equal propability.

3. There is no interactions between molecules (no collisions between molecules).

4. The molecules undergo elastic collisions with the walls.

You can change the following parameters
1. N: Total number of molecules

2. P: The presure of the system

3. v: The velocity of each molecules.

4. The width of the container (Click near the boundary and Drag the mouse)

The volume of the container is adjusted automatically according to the above parameters.
The animation is suspended when you press the mouse button. It is resumed when you release the button.
Try to find out the relations between
1. total number of molecules N ---- volume V

2. the pressure of the system P--- volume V

3. the velocity of the molecules v --- volume V