P 1 V 1 = P 2 V 2. Charles' Law: The pressure of a gas will change directly with the volume in which that gas is contained and vice versa. (This is very, very basic. We sill spend almost no time on this) (P 1 V 1)/T 1 = (P 2 V 2)/T 2Common Gas Law: The pressure and volume of a gas will change in direct relation to each other. The impact of changes in temperature is inversely preportional.