In this world, the things are exist in three states that are solid, liquid and gases. Every thing that we touch and have a definite shape, color and volume should be solid. In solid, the things made up of some material but the liquid are made up of ions and molecules like, water and the gases are exist in the outer atmosphere like carbon dioxide, carbon monoxide, nitrogen dioxide, hydrogen gas.

There are different types of solid, that are crystalline solid, amorphous solid and polymers solid. The crystalline solid are those solids which have definite shape, means molecules are arranged in a regular pattern and have a definite melting point like iron, copper and sodium chloride.

But in amorphous solid, the molecules are not arranged in a regular pattern and have no definite melting point like ordinary glass. Polymers solid consist and made up of long-chain organic molecules like rubber, wool, proteins and silk.

The mechanical properties of solid are that, solids have a ability to bend and rotate in a desired shape. In some solids, elasticity is present and which can be stretched out like rubber but some solids have no elasticity like steel, glass, stones.

Solid substance are very useful like, our homes and also the material of construction of homes buildings are also solid substance. All the things that are used in our daily life are solid in nature.