Concept
Evaporation
Overview
Evaporation is a type of vaporization that occurs on the surface of a liquid as it changes into the gas phase. A high concentration of the evaporating substance in the surrounding gas significantly slows down evaporation, such as when humidity affects rate of evaporation of water. When the molecules of the liquid collide, they transfer energy to each other based on how they collide. When a molecule near the surface absorbs enough energy to overcome the vapor pressure, it will escape and enter the surrounding air as a gas. When evaporation occurs, the energy removed from the vaporized liquid will reduce the temperature of the liquid, resulting in evaporative cooling.
On average, only a fraction of the molecules in a liquid have enough heat energy to escape from the liquid. The evaporation will continue until an equilibrium is reached when the evaporation of the liquid is equal to its condensation. In an enclosed environment, a liquid will evaporate until the surrounding air is saturated.
Evaporation is an essential part of the water cycle. The sun (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. Evaporation of water occurs when the surface of the liquid is exposed, allowing molecules to escape and form water vapor; this vapor can then rise up and form clouds. With sufficient energy, the liquid will turn into vapor.
Overview adapted from Wikipedia (CC BY-SA 4.0; see the article history for authors).
In the original texts
Passages from public-domain books where Evaporation is discussed.
In conformity with the mechanical theory of heat, it may be shown that evaporation is the escape of particles of water in the direction of least resistance; and that as the resistance (which is due to the pressure of the water diffused in a gaseous state) diminishes, the evaporation increases. Conversely, that rushing together of particles called condensation, which takes place when any portion of atmospheric vapour…
Herbert Spencer, First Principles
states what it is; names the idea; opens on it
Hence, in travelling, one may often see where a river runs, by a long bluish mist over it, though we are at such a distance as not to see the river itself. The quantity of this evaporation is greater or less, in proportion to the surface exposed by the same quantity of water to those causes of evaporation. While the river runs in a narrow, confined channel in the upper hilly country, only a small surface is exposed…
Benjamin Franklin, Memoirs of Benjamin Franklin
names the idea; states what it is
In some cases, indeed, it is only by the aid of conceptions derived from one class of phenomena that hypotheses respecting other classes can be formed. The theory, at one time favoured, that evaporation is a solution of water in air, was an assumption that the relation between water and air is _like_ the relation between salt and water; and could never have been conceived if the relation between salt and water had…
Herbert Spencer, Essays on education and kindred subjects
states what it is; names the idea
Tough Abbé Maury, when the obscure country Royalist grasps his hand with transport of thanks, answers, rolling his indomitable brazen head: ‘_Hélas, Monsieur_, all that I do here is as good as simply _nothing_.’ Gallant Faussigny, visible this one time in History, advances frantic, into the middle of the Hall, exclaiming: ‘There is but one way of dealing with it, and that is to fall sword in hand on those gentry…
Thomas Carlyle, The French Revolution
states what it is; names the idea
This becomes more equable when separated from fire and air, and then congeals into hail or ice, or the looser forms of hoar frost or snow. There are other waters which are called juices and are distilled through plants. Of these we may mention, first, wine, which warms the soul as well as the body; secondly, oily substances, as for example, oil or pitch; thirdly, honey, which relaxes the contracted parts of the…
Plato, Timaeus
states what it is
Philosophers who discussed Evaporation
Related ideas
Place in the tradition
Part of Anaximander.