We explain what evaporation is, how it intervenes in the water cycle and how it is used as a method of separating mixtures.

The heat causes the particles to come off in evaporation.

What is evaporation?

Evaporation is a physical process which consists of the gradual passage of a liquid to the gaseous state. It is a slow and silent transit, which occurs as a consequence of an increase in temperature. The reverse process is known as condensation (transition from gas to liquid).

By effect ofheat, themolecules of the liquid are agitated and acquire theEnergy necessary to get rid of the liquid, to overcome the binding energy that molecules have in the liquid state and transform into steam.

Evaporation can be observed, for example, in puddles that form after rain and then evaporate when the water comes out. Sun; also in the formation of clouds from the evaporation of river waters and oceans.

Evaporation and vaporization

When a liquid boils, the change in state affects its entire mass.

Vaporization is called the process of transformation of a substance from a liquid to a gaseous state. Evaporation is the phenomenon that occurs at any temperature, when the energy acquired by the substance is sufficient to overcome the surface tension of the liquid. The higher the temperature, the faster this process occurs. On the other hand, boiling occurs when all the liquid has reached a temperature such that it begins to boil.

Thus, evaporation is a process that is generated with increases in temperature below theBoiling point. If the process occurs from the boiling point, it is boiling: a rapid and violent process that occurs throughout the mass liquid.

The boiling point is reached when the vapor pressure of a liquid equals the atmospheric pressure that surrounds it. When this pressure level is reached, the liquid begins to boil and its molecules assume a gaseous state. Each liquid has a different boiling point. In the case of Water, the boiling point is 100º C.

Examples of evaporation

Some examples of this process of transformation from liquid to gaseous state:

  • Drying wet clothes in the sun.
  • The natural drying of damp hair after a bath or getting wet in the rain.
  • The gradual disappearance of sweat from our bodies, after working or exercising.
  • The formation of clouds over the waters of rivers and oceans.
  • The gradual drying of the I usually after being moped and scrubbed with water.
  • Obtaining sea salt from the evaporation of sea water in a saline.
  • The reduction and disappearance of the puddles that form with the rain, once it ends and the Sun.

Evaporation and the water cycle

Thanks to evaporation, clouds are formed and the humidity of the air is maintained.

The water cycle describes all the hydrological exchanges that occur between the atmosphere, the land and the sea through the three water states: the solid, liquid and gaseous.

The sun evaporates the water on the surface of the seas, lakes and rivers and this vapor, upon entering the heights of the atmosphere, condenses, transforming into liquid again.

This liquid descends towards the earth through a phenomenon known as precipitation that, in cold climates, can occur in a solid state of water such as snow or hail. In hot climates, liquid precipitation will occur in the form of rain.

From the water cycle we can deduce the enormous importance of solar evaporation of the planet's waters, which helps to produce the weather and renew the humidity of air and vegetation. Without this evaporation process life would not be possible on the Earth.

Evaporation as a method of separation

In science chemistry evaporation has been incorporated as a basic and very efficient method of separating a solution or mixture where they are a solute and a solvent.

The process is carried out by heating the solution until the solvent evaporates and leaves a solid residue. This naturally occurs with sea salt when the sun separates the water from the salt crystals at the seashore.

We can reproduce this separation process through a simple experiment, using a mixture of salt and water. To separate the salt from the salty water, the solution is heated in a beaker. While the water boils, we see how it escapes in the form of steam until it disappears completely, leaving only a layer of salt.

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