question_answer 35)

  Which condition out of the following will increase the evaporation of water (a) Increase in temperature of water                      (b) Decrease in temperature of water (c) Less exposed surface area of water                  (d) Adding common salt to water

Answer:

  (a) Increase in temperature of water will increase the evaporation of water. It is because, on increasing the temperature, kinetic energy of water molecules increases and more particles get enough kinetic energy to go into the vapour state. This increases the rate of evaporation. Evaporation is the surface phenomenon so it depends upon the exposed surface area. Higher the exposed surface area of water, higher will be the evaporation. When common salt is added to water then surface is occupied by the solvent as well as non-volatile solute particles. So, the escaping tendency of solvent particles decreases and thus the evaporation of water decreases. Therefore, other options (b), (c) and (d) will decrease the evaporation of water.