The phenomenon of the liquid gradually turning into vapour only from the surface at any temperature is called the evaporation of liquid.
The following are some important factors affecting the rate of evaporation.
Factors Affecting the Rate of Evaporation
(i) Surface area of the liquid: The greater the surface area of the liquid, the faster the evaporation.
(ii) Nature of liquid: Different liquids have different rates of evaporation. The lower the boiling point of the liquid, the higher the rate of evaporation. The evaporation rate of a volatile liquid is maximum.
(iii) Pressure on the liquid: As the atmospheric pressure on the liquid increases, the rate of evaporation decreases. Evaporation rate increases as pressure decreases. The evaporation rate is highest in a vacuum.
(iv) Air movement: Evaporation is accelerated by increasing air movement over the liquid.
(v) Elevation of liquid and liquid-adjacent air: Evaporation is accelerated when the volume of liquid and liquid-adjacent air increases.
(vi) Dryness of air: The drier the air above the liquid, i.e. the less water vapour in the air, the faster the evaporation.