Matter exists in three states which can be distinguished from one another by their characteristic properties.

Solid state

1. Generally, solids are very rigid.

2. Intermolecular space in solids is very small.

3. Attraction between the molecules is strong.

4. Solids have any number of free surfaces.

5. When heated or cooled, solids do not expand or contract very much.

6. Generally, the density of a solid is high.

7. When two solids are kept in contact, they do not diffuse into one another.

A solid is that state of matter which has a definite shape and volume.

Liquid state

1. Liquids are fluids. They can flow. They can take up the shape of the container in which they are stored.

2. Intermolecular space is greater in liquids than in solids due to which liquids are more compressible than solids.

3. Attraction between the molecules is less as compared with solids.

4. Liquids have only one free surface.

5. When heated or cooled, they expand and cool much more than solids.

6. The density of a liquid is relatively lower as compared to a solid.

7. If two liquids are mixed, then depending upon the nature of liquids, the particles of one can diffuse with the particles of the second liquid.

A liquid is that state of matter which has a definite mass and volume but no definite shape.

Gaseous state

1. Gases are fluids and occupy the entire space of the container in which they are kept.

2. Intermolecular space is very large in gases due to which gases are highly compressible.

3. Attraction between the molecules is the least in gases.

4. Gases have no free surfaces.

5. When heated or cooled, gases expand and contract to a large extent.

6. The density of a gas is almost negligible as compared to a solid or a liquid.

7. When two gases are mixed, their molecules rapidly diffuse into one another and form a homogeneous mixture. The large intermolecular spaces account for this property.

A gas is that state of matter which has a definite mass but no definite volume or shape.

Can matter change its state ?

Matter can change its physical state by change in temperature and pressure.