ideal gas whose pressure increases directly with the temperature and the density.

(See Ideal Gas).

a hypothetical gas with molecules of negligible size that exert no intermolecular forces

A hypothetical gas which obeys the gas laws of Boyle and Charles perfectly. For practical purposes the gases which compose unsaturated air may be considered perfect gases.

( Ideal Gas) A gas which obeys exactly the relationship pV = nRT. Such a gas is a hypothetical model of a real gas in which the particles have zero size, and there are no interactions between particles except perfectly elastic collisions when they collide with each other.