Density

If we hold cubes of equal volumes of different solids such as wood, aluminium, lead etc., we notice immediately that lead is heavy but wood and aluminium are light. We express this by saying that lead has a higher density than wood or aluminium.

Density is defined as mass per unit volume of a substance.

The SI unit of density is kilogram per cubic metre (kgmâˆ’3).

The CGS unit of density is gram per cubic centimetre [gcmâˆ’3].

• The density of a material varies with temperature and pressure.
• The variation of density with pressure for a gas is much more than that of a liquid because gases are more compressible than liquids. So density and pressure are related to each other.