Evaporation is the process through which water changes from a liquid to a gas or vapor. It is a primary pathway that helps water move from the liquid state back into the water cycle as atmospheric water vapor. Studies have shown that lakes, rivers, seas, oceans provide nearly 90 percent of the moisture in the atmosphere through evaporation, with the remaining 10 percent contributed by plant transpiration. A small amount of water vapor enters the atmosphere through sublimation. It is a process by which water changes from a solid to gas, bypassing the liquid state.
The Role of Heat in EvaporationHeat is essential for evaporation. Energy (in the form of heat) helps to break the bonds that hold water molecules together. It is why water can evaporate at the boiling point (212F/100C) but evaporates at a much slower rate at the freezing end of the spectrum. A state of saturation exists when the two process rates are equal, at which point the relative humidity of the air is a hundred percent.
Evaporation in everyday livesHere are a few examples of how evaporation benefits us in our daily lives:
- Drying clothes in the sun is one of the most common examples of evaporation. The water present in the clothes when they are washed (and hung on the line) is removed by the evaporation process.
- Crystallization is the process of obtaining crystals from the “mother” liquid. It takes place due to evaporation.
- The process of evaporation helps in food industries for processing pasta, milk, and other concentrates.
- The melting of an ice cube is an example of evaporation.
- If you ever find yourself stranded on an island in need of some salt, grab a bowl, add some seawater and wait for the sun to evaporate the water. What you’ll be left with (thanks to evaporation) is salt. One way to produce table salt is to evaporate saline water in evaporation ponds. This technique has been used by people for thousands of years.