SOLID STATE

The three states of matter : solid, liquid and gas are the result of molecular interaction.

For any substance to be in a particular state of matter is a matter of strength of intermolecular forces which when strongest bring the molecules closest (as much as possible) and substance adopts definite volume and shape at room temperature.

The same substance at three different temperatures

(ii) Temperature above its m.p. but below b.p.

Solids can be classified in two major categories on the basis of pattern of arrangement of constituent particles.

(a) Crystalline Solid; (b) Amorphous Solid

(a) Crystalline Solid: Solids in which constituent particles are arranged in long range ordered pattern. e.g. Salt, Diamond, Iodine

(b) Amorphous Solid: Solids in which pattern is short range ordered or disordered. e.g. Plastic, Glass, Rubber. Amorphous solid are also known as super cooled liquid.

Difference between Crystalline and Amorphous Solid

Property	Crystalline Solid	Amorphous Solid
1. Crystal Geometry	These have definite crystal shapes .	Do not have definite geometrical shape.
2. Symmetry	These can have (a) plane of symmetry (b) center of symmetry (c) axis of symmetry.	Do not have any symmetry.
3. Anisotropic or isotropic nature	In these, some properties are direction dependent e.g. refractive index i.e., these are anisotropic.	Properties are not direction dependent i.e.these are , Isotropic
4. Melting Point	Sharp M.P.	These have range of melting temperature.
5. Physical State	Hard and rigid	Soft
6. Crystal System	These have seven types of definite crystal systems.	These do not have regular crystal systems.