An ideal gas consists of a large number of identical molecules. The volume occupied by the molecules of an ideal gas is negligible compared to the volume occupied by a real gas. An ideal gas has identical particles of zero volume, with no intermolecular forces between them. The atoms or molecules in an ideal gas move at the same speed. Potential energy is zero in an ideal gas. The average kinetic energy of gas particles is proportional to the absolute temperature of the gas, and all gases at the same temperature have the same average kinetic energy