What is Evaporation?

Evaporation is a physical process by which a liquid substance slowly and gradually turns into a gaseous state. This process takes place on the surface of the liquid as a consequence of the release of the liquid molecules by the surface tension of the liquid.

Evaporation processes are constant in our environment and occur spontaneously.

An example would be the liquid that evaporates when we leave an uncovered glass of water for a few days, without having to boil it. Also if we leave a bottle of perfume uncovered, over time the liquid evaporates.

Evaporation, boiling and vaporization

boiling and evaporation

Left: steam escaping from the saucepan due to the boiling of the liquid content. Right: reservoir with low water level due to evaporation.

Evaporation, vaporization, and boiling are distinct physical processes in which a substance changes from a liquid to a gaseous state.

The evaporation it occurs slowly and at any temperature, affecting only the surface of a liquid.

The boiling occurs when the entire liquid mass reaches the temperature of the boiling point of the substance. At this point, most of the molecules are agitated, easily separated, and rapidly transition to the gaseous state.

The vaporization It refers to the process by which a substance is forced to change from a liquid to a gas.

Evaporation in the water cycle

Evaporation in the water cycle

Evaporation is the first phase of the water cycle and precedes condensation.

Evaporation is one of the phases of the hydrological cycle or water cycle.

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The water found in the oceans, on the earth’s surface and in vegetation, evaporates due to the effect of solar radiation and becomes part of the atmosphere.

The heat emitted by the sun causes the water molecules to shake with enough energy to break their bond and become steam.

Once in a gaseous state, it rises to the atmosphere where it condenses and forms clouds, fog or dew. Then it precipitates in the form of rain or snow and returns to the earth’s surface and the seas, where the cycle begins again.

See also:

  • Water cycle.
  • Condensation.

Evaporation as a separation method

Salinas

Lagoons of some salt pans from where, after the evaporation of seawater, salt is obtained.

It is a process that uses evaporation as a method to separate the substances that make up a mixture.

Generally, this mixture is made up of a solid substance dissolved in a liquid substance. Exposure to a heat source causes the liquid to evaporate, leaving the solid substance as residue.

An example of this process is obtaining salt, whose extraction is carried out in the salt pans, large expanses of shallow seawater. Exposure to the sun and wind causes the evaporation of the water, leaving the salt concentrated and crystallized.

Examples of evaporation

Examples of evaporation

Left: perfume concentrated by the effect of evaporation. Center: essential oil burner. Right: transpiration, vapor emission from vegetation.

concentrated perfume: over time, the alcohol in perfumes evaporates, leaving the essence concentrated and turning its color darker.

essential oil burner: the essential oil is mixed with water and subjected to the heat produced by the flame of a candle. That heat causes the mixture to evaporate and the essences of the oil to come off.

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water desalination: through the process called lightning, sudden or flash evaporation. It consists of subjecting water in the form of small drops to low pressure, which, after becoming steam, are condensed to obtain desalinated water.

evapotranspiration: is the joint process of releasing water vapor molecules into the atmosphere, from the transpiration of the vegetation and the evaporation of water from the surface of soils, rivers, lakes, etc.

The study of evapotranspiration is used in the field of agronomy to obtain the highest performance of water resources in the development of crops.

See also:

  • Changes of state of matter.
  • Boiling point.
  • Heat.

References:

  • King, C.J. (2021). Separation processes. reverse.
  • Lopez-Ortega, MS (2016). “the water cycle”: Didactic Unit for Early Childhood Education.
  • Manzur, A., & Cardoso, J. (2015). water evaporation rate. Mexican journal of physics E, 61(1), 31-34.
  • Vera, C. Camilloni, I. (2007). the water cycle. Ministry of Education, Science and Technology. Argentina.