EXPLANATION OF RELATIVE DENSITY
As you know, the density of a substance is defined as the mass of a unit volume. The unit of density is kilogram per meter cube (kgm–3). The density of a given substance, under specified conditions, remains the same. Therefore, the density of a substance is one of its characteristic properties. It is different for different substances. For example, the density of gold is 19300 kgm-3 while that of water is 1000 kgm-3. The density of a given sample of a substance can help us to determine its purity.
It is often convenient to express the density of a substance in comparison with that of water. The relative density of a substance is the ratio of its density to that of water:
Relative density = \(\frac{Density \,\,of \,\,a \,\,substance}{Density \,\,of \,\,a \,\,water}\)
Since the relative density is a ratio of similar quantities, it has no unit.
Illustration 10.7:
Relative density of silver is 10.8. The density of water is 103 kgm–3. What is the density of silver in SI unit?
Sol:
Relative density of silver = 10.8
Relative density = \(\frac{Density \,\,of\,\,silver }{Density \,\,of\,\,water}\)
Density of silver = Relative density of silver \(\times\) density of water
= 10.8 \(\times\)103 kgm–3
Source: This topic is taken from NCERT TEXTBOOK