Evaporation and condensation are both ways in which matter can change its state:

• – evaporation is where a liquid changes into a gas
• – condensation is where a gas changes into a liquid

Have you ever wondered how clothes dry outside on a hot day? This is due to evaporation. Liquid particles all have different energy levels. If a particle reaches a high enough energy level it’s able to escape from a liquid and form a gas. However, by doing so it takes away some of the energy from the remaining liquid and so the particles left have a lower kinetic energy than they did before and the liquid is colder. This is why when you sweat your skin is left cooler: for the sweat to evaporate it needs to take energy from your skin.

Particles in a gas also have different energy levels. If particles don’t have a high enough kinetic energy, for example if a gas is cooled down, then they move closer together and form bonds between one another. Instead of absorbing energy they release energy and become a liquid. This explains why on a cold day your windows become foggy and wet.

The rate of both evaporation and condensation are affected by temperature:

• – if the temperature of a gas decreases, condensation increases

• – if the temperature of a liquid increases, evaporation increases

Their rate also increases if:

• – air is moving over a liquid’s surface
• – the surface are of a liquid is increased