Question

give reason why gases have lower densities as compared to solids and liquids

Answer 1

because their intermolecular space is large .So they are very loosely packed .
Hope it helps u mate

Answer 2

This is because the molecules or atoms in a gas are much further apart than in a solid or a liquid.Gas molecules or atoms are usually flying around at very high speeds, occasionally bouncing off each other on the walls of the container the  gas is stored in. Hence,gases have lower densities as compared to solids and liquids.