What are states of matter?

Matter, the stuff everything is made of, usually exists in one of three states: solid, liquid or gas. A solid keeps its shape, a liquid flows and takes the shape of its container, and a gas spreads out to fill all the space it can. Heating or cooling can change matter from one state to another.

Examples

• Solid: ice keeps its shape.
• Liquid: water flows and fills a cup.
• Gas: steam spreads out into the air.

Quick facts

• Water is the everyday example: ice (solid), water (liquid) and steam (gas).
• Heating melts a solid into a liquid; cooling freezes it back.