Evaporation

Evaporation is the process by which molecules in a liquid state (e.g. water) spontaneously become gaseous (e.g. water vapor), without being heated to boiling point. It is the opposite of condensation. Generally, evaporation can be seen by the gradual disappearance of a liquid, when exposed to a significant volume of gas.
The reason a liquid evaporates is that its molecules are all in motion in nearly random directions and speeds, and the energy of that movement can be compared to the heat needed to boil that liquid. On average, none of the molecules have enough energy to be considered "boiling", or else the liquid would turn into vapor quickly. When the molecules collide, they transfer energy to each other in varying degrees, based on how they collide. Sometimes the transfer is so one-sided that one of the molecules ends up with enough energy to be considered past the boiling point of the liquid. If this happens near the surface of the liquid it may actually fly off into the gas and thus "evaporate".
Liquids that do not appear to evaporate visibly at a given temperature in a given gas (e.g. cooking oil at room temperature) have molecules that do not tend to transfer energy to each other in a pattern sufficient to frequently give a molecule the "escape velocity" - the heat energy - necessary to turn into vapor. However, these liquids are evaporating, it's just that the process is much slower and thus significantly less visible.
Evaporation is an essential part of the water cycle. Solar energy drives evaporation of water from oceans, lakes, moisture in the soil, and other sources of water. In hydrology, evaporation and transpiration (which involves evaporation within plant stomata) are collectively termed evapotranspiration.
Contents[hide]
1 Theory
1.1 Evaporative equilibrium
2 Factors influencing the rate of evaporation
3 Applications
3.1 Combustion vaporisation
3.2 Film deposition
4 See also
5 References
6 External links
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For Further Reading Click on D Hyperlinks....