Solid:- A solid is defined as the substances which possess rigidity have a definite shape and size.
Example: Book, Sodium, Calsium etc. The main point in which the solid differ from the gases and liquids is that they possess fluidity and solid does not.
CAUSE OF EXISTENCE OF SOME SUBSTANCES AS SOLIDS:-
1. Intermolecular Forces:-
These are the forces existing among the constituent particles of substance which keep them close together.
2. Thermal energy:-
This is the energy possessed by the constituent particles molecules apart as it tends to make them move fast. As low temperature intermolecular forces are strong and thermal energy is low. Thus the constituent particles only oscillate about their mean position and substance exists as solid.
GENERAL CHATERISTICS OF SOLID STATE:-
Solids possess following properties:-
The constituent particles are very closely packed and the intermolecular distances are very small.
The constituent particles occupy fixed positions and they can only oscillate about their mean positions.