States of matter

 How do we classify matter?

Matter is found as a solid, liquid or gas.

Solids have a fixed shape, mass and volume. We can change the properties of the object by using force or heat. 

 Liquids don’t have a fixed shape. They take the shape of the container. They keep the same mass and volume unless we heat them. 

Gases have a fixed mass, but they don’t have a fixed shape or volume. Gases expand to fill the space around them.

El estado plasma

How can matter change?

We can change the shape of matter by applying a force. If we squeeze a plastic bottle, we change its shape. We can change the state of matter by heating or cooling it. When we burn a candle, the wax melts and becomes a liquid. When it cools down, it becomes a solid again.

What are the three states of water?

Liquid water freezes at 0 degrees celsius (0oC) and becomes solid water. Ice is solid water. When we heat ice, it melts and becomes liquid water. Liquid water becomes a gas when we heat it. Water boils and the gas, called water vapour, evaporates into the air. When water vapour cools down, it condenses and becomes liquid water again.

What is combustion?

Matter changes when we burn it. When something burns there is a chemical reaction called combustion that produces light and heat. Three elements are involved in combustion. 

 • The material that burns is the fuel. We often use wood or coal. 

 • A spark or small flame starts the process. 

 • Oxygen combines with the fuel and this produces a change.

 For example, burning wood becomes ash . Smoke is released into the air. Smoke is made up of different gases.