The Solid state

The Solid state

The matter exists in three states- solid, liquid, gas. They differ in the interparticle spaces which are the least in the solids and maximum in the gas. The liquids and gases are quite often called as fluids while solids are not. A substance is said to be in the solid state if its melting point is above the room temperature under the atmospheric pressure.

The temperature at which a solid melts under normal pressure (1 atmosphere) is known as melting point.

A solid is defined as that form of matter which possesses rigidity and hence possesses a definite shape and a definite volume.
The liquids and gases are quite often called as fluids while solids are not. Unlike gases and liquids in which the molecules are free to move about and hence constitute fluid state, in solids the constituent particles are not free to move but oscillate about their fixed positions.

Characteristic properties of the solids

·         They have definite mass, volume and shape.

·         Intermolecular distances are short.

·         Intermolecular forces are strong.

·         Their constituent particles (atoms, molecules or ions) have fixed positions and can only vibrate about their mean positions.

·         They are incompressible and rigid.

The main objectives of the chapter are:

·         Classification of Solids

·         Crystal Lattices and Unit Cells

·         Calculation of number of particles per unit cell

·         Close packing in crystals

·         Tetrahedral and octahedral voids.

·         Packing Fractions

·         Imperfections in Solids and defects in Crystals

·         Properties of Solids