Example of an Evaporation Sentence Water evaporation occurred from the leaf. The yearly evaporation from water surfaces ranges between 60 and 150 inches. To avoid evaporation, the test tube is firmly corked and left to stand for many hours. Evaporation is the process by which water vapor leaves liquid water. As water evaporates, it becomes a gas. Evaporation can occur from any surface on which liquid water exists, including soil, rocks, plants, and people. It is important in humid climates like those found in most parts of the world because it removes water that would otherwise cause problems for plants and animals. Evaporation also plays a role in creating clouds. When clouds form through evaporation, they contain more ice than air, which means they are cold enough to fall as snow or hail rather than being hot enough to remain aloft as bubbles or droplets. In science classes, experiments are often performed to study evaporation. For example, students may be asked to measure the amount of water lost by pouring different liquids such as milk, juice, or alcohol into containers with holes in their lids. The volume of these liquids decreases as water is lost through evaporation. This is because energy is needed to break up the molecules of the liquid so that they can become gases.