Matter: states, elements, compounds and mixtures

Matter is anything that has mass and takes up space.

The three states of matter

• Solids: particles packed closely in a fixed pattern; they vibrate. Fixed shape and volume.
• Liquids: particles close but able to move past each other. Fixed volume, no fixed shape.
• Gases: particles far apart and moving fast in all directions. No fixed shape or volume.

Changes of state: melting, freezing, boiling/evaporation, condensation and sublimation (solid straight to gas). Diffusion is the spreading of particles from high to low concentration – the smell of cooking spreads through a room.

Elements, compounds and mixtures

• An element contains only one type of atom, e.g. oxygen (O), iron (Fe), copper (Cu).
• A compound contains two or more elements chemically joined in a fixed ratio, e.g. water (H₂O), sodium chloride (NaCl). It has different properties from its elements.
• A mixture contains substances not chemically joined, e.g. air, salty water, soil. It can be separated by physical methods.

Metals and non-metals

Metals are shiny, good conductors of heat and electricity, malleable and ductile. Most non-metals are dull and poor conductors (graphite is an exception – it conducts).

Check yourself

1. Describe the arrangement and movement of particles in a gas.
2. State one difference between a compound and a mixture.
3. Name the change of state from gas to liquid.