States of matter

All matter is made of tiny things called particles. Whether matter is solid, liquid or gas depends on the way these particles behave.

Solids

The particles in a solid are tightly packed together. Each particle stays in its position. Because of this, solids have a definite shape. This means that if you place a solid object in a container, it will NOT change its shape to fit the container. Solids also have a definite mass and a definite volume. Wood and rocks are examples of solids. Can you name some solids seen in the picture below?

Liquids

In liquids, the particles are not very tightly packed together. They can flow around each other. Because of this, liquids DO NOT have a definite shape. If you put a liquid in a container, it will take the shape of that container. A liquid has a definite mass and volume even though it DOES NOT have a definite shape. Water and oil are examples of liquids.

^{Liquids take the shape of their container.} 

Gases

In a gas, the particles have a lot of space in between them. They have a lot of freedom to move. If placed in a container, the gas will expand to fill the container. A gas DOES NOT have a definite shape. A gas DOES NOT have a definite volume. However, gas has a definite mass. Oxygen and water vapour are examples of gases. 

The diagram below shows how particles behave in solids, liquids and gases.