Evaporation and Condensation _ GCSE Physics

Evaporation involves a liquid changing into a gas. The particles in a liquid have different energies, some will have enough energy to escape from the liquid and become a gas whilst the remaining particles in the liquid have a lower average kinetic energy so will stay there and the liquid will cool down as evaporation happens. This is why sweating cools you down, by leaving behind the cooler liquid on your skin. The sweat absorbs energy from your skin so that it can continue to evaporate and cool you down even more. The rate of evaporation increases if the temperature of the liquid is increased, if the surface area of the liquid is larger or the air moving over the surface is more violent. Condensation involves a gas turning into a liquid. The particles in a gas have different energies. Some may not have enough energy to remain as separate particles, particularly if the gas is cooled down. this causes them to come close together and bonds form between them. Energy is released when this happens. This is why steam touching your skin can cause scalds: not only is the steam hot, but energy is released into your skin as the steam condenses which only adds to the pain.