States of Matter & Changes

Everything around you is made of matter, and matter usually shows up in one of three familiar states: solid, liquid, or gas. The state depends on how the tiny particles inside are arranged and how fast they are moving. Add or remove energy (usually heat) and matter can change from one state to another.

The Three States of Matter

• Solid — particles are packed tightly in a fixed pattern. They vibrate in place. A solid keeps its own shape and volume.
• Liquid — particles are close together but can slide past each other. A liquid takes the shape of its container but keeps its volume.
• Gas — particles are far apart and move quickly in every direction. A gas spreads out to fill its whole container.

The Six Phase Changes

When energy is added, particles move faster and the state shifts toward gas. When energy is removed, particles slow down and the state shifts toward solid. There are six named changes of state.

• Melting — solid to liquid (heat added). Example: an ice cube turning to water.
• Freezing — liquid to solid (heat removed). Example: water in a tray becoming ice.
• Evaporation — liquid to gas (heat added). Example: a puddle drying up in the sun.
• Condensation — gas to liquid (heat removed). Example: water drops on a cold glass.
• Sublimation — solid straight to gas (heat added). Example: dry ice turning into carbon dioxide gas.
• Deposition — gas straight to solid (heat removed). Example: frost forming on a window.