Kinetic Theory Apparatus.

The IEC Kinetic Theory apparatus is a robust demonstrator for the movement of molecules in a gas. A strong DC motor is connected to a vibrating platform inside an acrylic tube with a scale. The platform has a rubber surface and a set of 100 small stainless steel balls is loaded into the tube. As the motor is changed in speed (simulating the heating of a gas), the agitation of the balls changes inside the tube.

A light polystyrene foam disc is placed in the tube and it 'floats' on the agitated balls at a certain height. A second heavier disc can be added or can replace the first.
An approximate relationship between the floating height (volume of the gas) and the weight of the discs (pressure of the gas) can be seen.