Evaporation is the escape from the surface of a liquid of the molecules that, because of thermal (heat) agitation, are moving with enough velocity to break the surface tension of the liquid. As the heat contained in a liquid increases, the activity of its molecules and the evaporation also increase.
A practical limit is placed on the amount of evaporation by the concentration of molecules as vapor in the atmosphere around the liquid. The sealing of a container of liquid, such as a jar, restricts the atmosphere into which the molecules can escape. This atmosphere is quickly saturated by the molecules of the liquid, thus halting evaporation and preventing the drying of the contents of the jar.