Gas Model is a transparent plastic cylinder with bouncing balls activated by a vibrating plate. The moving balls lift a disk to a height which depends on the amount of energy introduced by the vibrating plate. This exhibit demonstrates the properties of molecules of a gas. The bouncing balls represent molecules of a warm gas. When a gas is heated, energy is added. This energy can raise the temperature of the gas by increasing the motion of the molecules. The effect is seen when boiling a lidded pot of water—it's the energy in the heated gas (water vapor and air) at the top of the pot that can lift up the pot lid. On the other hand, if the temperature of a substance is lowered to absolute zero, the molecules will stop moving.