A matter is anything that has mass, occupies space and can be perceived by our senses. For example, the water we drink and the clothes we wear are the matters.

There are some forces of attraction between the particles of matter which bind them together. The force of attraction between the particles of the same substance is known as cohesion. The force of attraction (or cohesion) is different in the particles of different kinds of matter. The forces of attraction tend to hold the particles together and control their movements. The interparticle forces of attraction are the maximum when the particles are close together. As the distances (or spaces) between the particles of matter increase, the forces of attraction between them decrease.

The process by which a solid changes into a liquid is called melting. On heating, ice melts into water. The temperature at which a given solid will melt is called melting point.

The process in which the substance in liquid phase changes into a solid phase by losing some of its energy is called freezing. During freezing, the volume increases. Freezing of water takes place at 0 ° C temperature.

Conversion of water vapours which is the gaseous state to water its liquid state on cooling, is called condensation. When we put ice-cold water in a glass, we can see water droplets outside the glass. This is due to the condensation of water vapour when it comes in contact with the cold surface. So, the process of changing a gas (or vapour) to a liquid by cooling is known as condensation.