S.I. unit of density is kg/m3
The relative density of a substance is the ratio of its density to that of water
Density of water
Relative Density=——————————- * —————————-
Volume of substance Mass of water
Relative density of substance=————————-
Mass of water
For Ex:Relative density of iron is 7.8 means iron is 7.8 times heavy as an equal volume of water.
Relative density has no units.
Density of a substance is one of its characteristic property and is different for different substances.