From Latin evaporatio, the evaporation is the action and effect of evaporating or evaporating . This verb, meanwhile, refers to the transformation of a liquid into steam .
During the process Physical called evaporation, a liquid substance slowly and gradually passes into a gaseous state, once it has acquired the energy needed to increase its surface. It is important not to confuse this term with boiling, since evaporation does not require a particular temperature; even more, the greater this one, the earlier it will take place.
It is worth mentioning that it is a phenomenon absolutely necessary for the life cycle, since the water in a gaseous state condenses and becomes clouds, which recover their liquid form during the rain, which keeps our soil fertile. Also this return of water to earth It can occur through snowfall, dew or fog.
On surface of a liquid substance, unless there is an obstruction, a portion of its molecules are in a gaseous state; When this is balanced, the pressure of the saturating gas phase is established, which is not directly related to the volume, but to the temperature and the type of liquid. If the amount of gas is less than that pressure, then evaporation takes place, since a percentage of the molecules change state; on the other hand, if the pressure is equal to that of the atmosphere, the boiling occurs.
When very few molecules are close to the surface and performing a correctly directed movement to get out of the liquid at some point, the evaporation rate is limited. Moreover, given that the ones that manage to escape are the ones that have the most Energy that the rest, the substance undergoes a considerable reduction of its temperature (this is called evaporative cooling, and takes place during the phenomenon of sweating).
With regard to sweat, it should be noted that during evaporation it is eliminated more than twenty percent of the heat of our body, since the Water It has a particularly high specific heat and the energy it requires to evaporate the rest of our body, causing its temperature to decrease. More specifically, to eliminate 1 g of sweat are necessary 0.58 kcal; these are obtained from the skin, which causes it to cool and eventually affect body temperature. When a stream of dry air replaces the wet one, an increase in evaporation is seen.
It is possible to distinguish between insensitive evaporation, which is given through our tissue cutaneous (when the air humidity does not reach 100 percent) and through the nostrils, and surface evaporation, which comes from the sweat glands, which exist in many parts of our body, but especially in the groin area, the armpits, the forehead and the palms of the hands and feet.
If evaporation takes place in a closed container, those molecules that manage to escape from the liquid are grouped in gas state on top of it and many of them return to their liquid form. When this round-trip process reaches a balance (called evaporative) there are no more changes in the vapor pressure (which in this case is called saturated) or at the temperature of the substance.
For hydrology, science natural that studies the waters, evaporation is considered a very significant variable when looking to calculate the water balance (the relationship between the input and output water resources during a specific period of time) of the river basins, whether total or partial, taking into account their area of origin.