As the volume of a gas or liquid its density decreases

Density is related to mass and volume as;

                                   Density  =  Mass / Volume

Above relationship shows that Density is directly proportional to Mass and inversely related to Volume. Therefore, increasing the mass increases density and vice versa, and decreasing volume will increase density and vice versa.

Result:
          As the volume of a gas or liquid Increases, its density decreases.