Question

Differentiate between density and relative density of a substance?

Answer 1

Hint: We know that when we are defining the relative density, we should always mention the standard substance under some specific conditions. In case of solids and liquids the standard material is usually taken as water which is at a temperature of 4 degree Celsius or can be under some other mentioned temperature.

Complete answer:
We know that density of a substance is defined as the mass of that substance that will be taken in consideration per unit volume.
The expression for the density of a substance can be given as: ${\displaystyle \frac{\text{mass of substance}}{\text{ volume of substance}}}$.
Density is also expressed as: ${\displaystyle \frac{m}{v}}={\displaystyle \frac{Mass}{Volume}}$
On the other hand, the relative density of a substance is defined as the ratio between the density of that substance and the density of the water.
The expression for the relative density of a substance can be given as: ${\displaystyle \frac{\text{ Density of substance }}{\text{ Density of water}}}$.
Moreover, one more difference between density and relative density is that, the SI unit of density is given as: $\mathrm{kg}/{\mathrm{m}}^3$.
On the other hand, since relative density is a ratio, it has no units.

Note: We should know that in case the relative density is 1 then the densities are always equal. This signifies that the volume of the two substances will be same, thus the mass will also be the same. In case the material taken as reference is water then the substance whose relative density if less than 1 will always float on water. Relative density can also be defined as the density of the substance divided by the density of water at 4 degree Celsius.