IGCSE Chemistry: Changes of states - 1.2

Melting

Solid → Liquid

Freezing

Liquid → Solid

Boiling / Vaporisation

Liquid → Gas

Condensation

Gas → Liquid

Sublimation

Solid → Gas

Solidification

Gas → Solid

Melting Process

Heat the solid. Particles gain kinetic energy. They vibrate faster. Eventually vibrations overcome the forces of attraction. Particles leave their regular pattern and can slide past each other.

Freezing Process

Cool the liquid. Particles lose kinetic energy. They can no longer slide past each other. Attractive forces hold them in a regular pattern.

Evaporation / Boiling Process

Heat the liquid. Particles gain kinetic energy. They move further apart. Attractive forces are broken. Gaseous particles escape.

Condensation Process

Cool the gas. Particles lose kinetic energy. Attractive forces become strong enough to keep particles closer together.

Sublimation Process

Heat the solid. Particles gain kinetic energy. They vibrate faster. Forces of attraction are completely broken. Particles escape as a gas.

Melting Point

Temperature at which a solid starts to melt. Water/ice melting point = 0°C.

Boiling Point

Temperature at which a liquid boils. Water boiling point = 100°C.

Evaporation

Liquid → gas below its boiling point. Happens at the surface.

Volatile

A liquid that evaporates at room temperature.