**Relative Density**

Density is the ratio between the mass and the volume of a body. Relative density is the ratio between the density of an object and the density of some other reference object at some given temperature.

\(Density(\rho )\,\,=\,\,\frac{Mass(m)}{Volume(V)}\).

**What is a Relative Density?**

Relative density also known as specific gravity, it is the ratio of density of any substance (Solid, Liquid and Gas) at given temperature and pressure to the density of water at 1 atm and 4°C is called as density of that substance at that temperature and pressure.

Relative density of a Substance = \(\frac{Density\,\,of\,\,the\,\,subs\tan ce}{Density\,\,of\,\,water}\).

Let’s take the density of honey is 1.42 g/ cm³ and Density of water is 1 g/ cm³. So,

Specific gravity = \(\frac{Density\,\,of\,\,the\,\,subs\tan ce}{Density\,\,of\,\,water}\).

Therefore, specific gravity does not have a unit and hence specific gravity is a dimensionless physical quantity. The specific gravity of a substance will let us know if it will float or sink, it given us the idea about relative mass or relative density. If the specific gravity of a substance is below 1 then it will float and if it is greater than 1 it will sink.

**For Example: **Relative density of Iron = \(\frac{Density\,\,of\,\,Iron}{Density\,\,of\,\,Water}\,\,=\,\,\frac{8500kg/{{m}^{3}}}{1000kg/{{m}^{3}}}\,\,=\,\,8.5\).

Thus, the Relative density of Iron is 8.5.