Some of the properties of solids, liquids and gases can be explained n the basis of their interaction energy and thermal energy as follows :
1. A solid has rigidity because thermal motion is too weak to overpower the strong intermolecular forces of attraction. In a gas, thermal energy is so high that the molecules cannot come close together. Hence, there are large empty spaces between them. In a liquid, there is a reasonable balance between the attractive intermoleculr forces and thermal energy. Hence, molecules in a liquid exist together, i.e., it is a condensed state of matter but there is no rigidity. That is why they have no definite shape.
2. A solid melts on heating because on heating, the thermal motion increases.
3. In both liquids and solid, their molecules exist together, i.e., both of them are condensed state of matter having sufficiently strong intermolecular forces of attraction. Hence, they exhibitve very low compressibility. On the other hand in gases, there are large empty spaces between the molecules, therefore, they possess high compressibility.