Question

Difference between solids,liquids and gases

Answer 1

Solid is a state of matter in whch the molecules are tightly packed.They are rigid

liquid is a state of matter in which the molecules are loosely packed as compared to solids

gases is the state of matter in which the molecules are freely packed as compared to solids and liquids

Answer 2

Solid has definite shape, distinct boundaries and fixed volumes.So, they are rigid.
Liquid has no fixed shape but has a fixed volume. Liquids flow and change shape, so they are not rigid but can be called fluid. 
Gaseous have no fixed shape and no fixed volume. It is compressible for example LPG, CNG gas, etc.