Spark image

The molecules in a liquid are in a state of continuous motion, some moving faster than others. In the middle of the liquid they collide with each other but at the surface of the liquid some of them are going fast enough to escape from the liquid. We call this EVAPORATION.

Of course the molecules need energy to escape and so the hotter the liquid becomes the more evaporation there is. Notice that it is only the surface molecules that evaporate and there are no bubbles of gas formed in the body of liquid. Evaporation is very important in the cooling of surfaces and the cooling of our bodies by sweating.

© Keith Gibbs 2009