This animation illustrates the concept of the free path length of molecules in a gas.

Brownian motion. The chaotic motion of a minute particle suspended in a gas or liquid.

Boltzman Distribution. The behaviour of the gas molecules under the action of gravity.

Compression and expansion of an adiabatically isolated gas is accompanied by its heating and cooling.

Thermal oscillation of a piston in the presence of gas.

The Maxwell Distribution. An experiment with a Galton board demonstrates the statistical sense of the Maxwell distribution.

Molecular structures.

The increase in the Earth's positive surface charge is cancelled out by the flow of negative electrons from the clouds which we can see in the form of lightning bolts.