Matter Study Guide Terms to Know Matter – anything that takes up space and has mass Mass – is a measure of the amount of matter Volume – the amount of space an object takes up Physical Changes – when matter changes from one state of matter to another Melting – when a solid changes into a liquid by adding heat (the temperature goes up) Freezing – when a liquid changes into a solid when the temperature goes down. Condensation When water vapor (gas) turns to water (liquid), like the mirror in your bathroom after a hot shower. Concepts to Remember Matter most commonly occurs in three states: solids, liquids, and gases. You should be able to give an example for each. Matter can change from one state to another. When matter changes from one state to another, these changes are referred to as physical changes.