Density

Density (ρ) of any substance can be defined as the mass per unit volume or

                      density = mass / volume

                               ρ = m / v

Relative density

 The ratio of density of substance to the density of water at 4°C is called relative density or specific gravity.

    Relative density = density of substance / density of water at 4°C .

 

Note :  Relative density is a pure ratio. So, it has no units. 

            Density of water at 4°C in CGS is 1 g/cm3 . Therefore, numerically the relative density  and density of substance (in CGS) are equal. 

exam: Relative density of an oil is 0.6. find the absolute density in CGS and SI unit.

sol:  Density of oil (in CGS) = relative density (g/cm3) 

                     absolute density = 0.6 g/cm3

                        absolute density = 600 kg/m3

                                                         https://youtu.be/UCHIvvAvekA