Normally matter exists in three forms:
Heat energy can bring about a change of state in matter from solid to liquid and liquid to gaseous state.
Suppose a solid is heated continuously at constant pressure, its temperature goes on increasing till it starts melting. The temperature does not increase further until all the solid melts into liquid. This temperature is known as 'The melting point' of a solid. Melting point is a characteristic property of a given solid. Melting point is a very sharp temperature of a pure solid and hence, by determining the melting point, purity of a solid may be tested.
