Discuss the three states of matter: solid, liquid and gas on the basis of molecular model.

Molecular Model of Solids

The molecular model of solids is shown in the figure below:

1. Each solid is made up of very tiny particles called molecules that are in a rigid arrangement.
2. The inter-molecular space is very small incase of solids.
3. The molecules in a solid can only vibrate to and fro about their mean positions. They do not leave their positions.
4. The molecules in a solid are closely packed due to strong inter-molecular force of attraction between them.
5. Solids have definite shape and volume.

Molecular Model of Liquids

The molecular model of liquids is shown in the figure below:

1. Each liquid is made up of very tiny particles called molecules that are not in a rigid arrangement.
2. The inter-molecular spaces in liquids are more than that in solids.
3. The molecules in a liquid are less closely packed and their positions are not fixed as they are free to move within the boundary of the vessel in which the liquid is kept.
4. Although the inter-molecular force of attraction is weak as compared to solids but it is sufficient to keep them within the boundary of the vessel.
5. Liquids have definite volume but no definite shape.

Molecular Model of Gases

The molecular model of gases is shown in the figure below:

1. Gases are made up of very tiny particles called molecules that are not in a rigid arrangement.
2. In gases the inter-molecular space is maximum and the force of attraction is least as compared to solids and liquids.
3. The position of these molecules are not fixed. The molecules can move randomly anywhere due to weak inter-molecular forces.
4. Gases have neither definite shape nor definite volume.