Density and relative density

Density is the ratio of the mass to the volume of a body. Relative density, on the other hand, is the ratio of the density of an object and the density of some other reference object (usually water) at some given temperature. Density is measured in
kg/m³. Density is unique for each body, while the same body can have numerous relative densities (compared to different reference bodies). The density (ρ) of an object can be defined mathematically as the mass (m) divided by the volume (V):

The relative density (RD) or specific gravity (SG) of a substance is the ratio of density of a substance to the density of water at 4^oC. Since the units for both the numerator and denominator are same, they cancel each other. Thus relative density has no units.

Key Terms

• Pressure is defined as the amount of force exerted on a surface per unit area.
• The density (ρ) of a substance can be defined mathematically as the mass divided by the volume.
• The relative density (RD) of a substance is the ratio of density of a substance to the density of water at 4^oC.