What is Evaporation?

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Evaporation refers to the process through which water transforms from liquid form to vapor of gas. It is the only way that water changes from liquid form so it can get back to water cycle in the atmosphere as vapor. Studies show seas, rivers, lakes and oceans contribute an estimated 90% of atmospheric moisture through evaporation while transpiration from plants contributes 10%. There is an extremely small quantity of vapor entering the atmosphere via sublimation. Sublimation is a process through which water is changed from solid state, which is ice, into gas. Sublimation allows water to bypass the liquid state and usually happens around the Rocky Mountains as well as when Chinook winds blow from the Pacific ocean towards the end of winter and beginning of spring. Blowing of Chinook winds causes a dramatic rise of temperatures within hours. The air blows on snow converting it directly into vapor. Sublimation causes disappearance of snow pretty fast in arid areas.

How Evaporation Happens

Heat, which is energy, has to be present for evaporation to happen. It is the energy that breaks bonds that join water molecules. This explains why water evaporates easily when it reaches boiling point by at freezing point, the evaporation rate is very slow. Net evaporation happens when the evaporation rate is higher than the condensation rate. When these two rates equalize, saturation occurs. Humidity level in the air is usually at 100% during saturation. Condensation, which is the direct opposite of vaporization, happens when the amount of air that is saturated is cooled beyond dew point. Dew point refers to the temperature at which air is cooled under continuous pressure to it becomes saturated fully with water. As a matter of fact evaporation extracts heat from the atmosphere. That explains the cooling effect that evaporation of water from the skin has on the human body.

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