# Matter in our Surroundings

## States of matter:

On the basis of physical state, all the matter can be classified into three groups: Solids, Liquids and Gases.

### Properties of Solids, Liquids and Gases:

S.No. Solids Liquids Gases
1. Solids have a fixed shape and fixed volume Liquids have fixed volume but they have no fixed shape Gases have neither a fixed shape nor a fixed volume
2. Solids cannot be compressed much Liquids cannot be compressed much Gases can be compressed easily
3. Solids have high densities Liquids have moderate to high densities Gases have very low densities
4. Solids do not fill their container completely Liquids do not fill their container completely Gases fill their container completely
5. Solids do not flow Liquids generally flow easily Gases flow easily
6. For example: Ice, coal, wood, stone, iron, etc. Water, milk, fruit juice, ink, petrol, etc. Air, oxygen, hydrogen, nitrogen, steam, etc.

### Why Solids, Liquids and Gases have different properties:

• According to the kinetic theory of matter, the particles of matter are in continuous motion and possess kinetic energy.
• Some forces of attraction also exist between the particles of matter. These are called inter particle forces. The forces of attraction tend to hold the particles together and control their movements.

### The following properties of particles decide whether a given substance will exist as a solid, a liquid or a gas:

1. The spaces between the particles: the spaces between the particles are the minimum in solids, a little more in liquids, and the maximum in gases.
2. The force of attraction between particles: the forces of attraction between the particles are the strongest in solids, less strong in liquids and negligible in gases.
3. The amount of movement of particles (or kinetic energy of particles): the movement of particles is the minimum in solids, more in liquids and the maximum in gases.