Free Chemistry Dictionary

Video Example : Evaporation



  • Evaporation
  • Condensation
  • Surface phenomenon
  • Humidity
  • Surface area
  • Forces of attraction

Definition of Evaporation

Evaporation is a type of vaporization of a liquid that occurs from the surface of a liquid into a gaseous phase that is not saturated with the evaporating substance.

More About Evaporation

  • The other type of vaporization is boiling, which is characterized by bubbles of saturated vapor forming in the liquid phase
  • Steam produced in a boiler is another example of evaporation occurring in a saturated vapor phase
  • A fraction of the molecules in a glass of water have enough heat energy to escape from the liquid
  • Particles of matter are always moving and never at rest
  • At a given temperature in a given solid, there are always particles with different amounts of kinetic energy
  • In liquids, a fraction of molecules with higher kinetic energy break into the space by overcoming forces of attraction and they go into vapor phase, that is, they evaporate
  • The phenomenon of changing of liquid into vapour at a temperature below its boiling point is called “Evaporation”
  • Rate of evaporation increases with
  • Increase in temperature. With the increase in temperature more number of particles attain greater amount of kinetic energy and they break up from liquid phase
  • An increase in surface area. We need to spread out wet things such as wet clothes (as in India) so that they can dry faster
  • A decrease in humidity: The air around us cannot hold more than certain amount of water vapor. If the humidity in the atmosphere is great, rate of evaporation increases
  • An increase in wind speed: when the speed of the wind is high, it carries with it humidity, due to which rate of evaporation increases

Applications of Evaporation:

  • When liquid evaporates from an open vessel, the particles of liquid absorb energy from surroundings to regain energy lost during evaporation. This absorption of energy from surroundings makes the surrounding areas cold
  • When a small quantity of acetone is poured into our palm, acetone evaporates and absorbs energy from our palm making the palm to feel cold
  • Let us take some ice cold water in a tumbler. We can see water droplets on the tumbler. The water vapor present in the air, on coming in contact with the cold glass of water, loses energy and gets converted to liquid state, which is seen as water droplets
  • People should wear cotton clothes in summer in India as, due to heat, there is lot of perspiration, and cotton absorbs the sweat from bodies and it keeps the bodies cool
  • Evaporation of water from the earth keeps the air moist and provides the moisture for clouds. Thus evaporation has an important influence on weather and climate