Lesson 3: The three states of matter

States of matter refers to the different forms in which a matter can exist. In broader terms, there are four different states of matter namely solid, liquid, gas, and plasma.  Matter in different states exhibit distinct physical and chemical properties. While a matter in a solid has a fixed volume and shape, it loses its shape in liquid form, but its volume remains the same. In gaseous state, both the volume and shape are not fixed. 

The particles in a solid:

• sit very closely together.
• are in a regular arrangement and in fixed position.
• vibrate about a fixed position but do not move through the solid.
• are held together by strong forces.

This explains why solids have a fixed shape and volume.

Figure 2: the particle arrangement in a solid

Liquids

The particles in a liquid:

• sit close together but have some gaps.
• can move past each other because of the gaps.
• have enough energy to prevent the forces between them holding them in a fixed, regular arrangement.
• are randomly arranged.

This explains why liquids have a fixed volume but take on the shape of their container.

Gases

The particles in a gas:

• are much further apart than in a solid or liquid.
• are entirely free to move because the forces between them are weak.
• are randomly arranged.
• move quickly and randomly in all directions.

This explains why gases completely fill their container and have the same volume as their container.