Question

What is Evaporation? What are the factors affecting it?

Answer 1

Hint: Evaporation is nothing but the vaporization, which occurs on the liquid surface. Here the molecules on the liquid surface jump into a gaseous phase. Evaporation of any liquid depends on the amount of surface area exposed to air, temperature, pressure, substance dissolved in it and concentration of the substance that is evaporating, in the air.

Complete answer:
If we consider the container containing some amount of liquid, the molecules of the liquid are not still, they are in continuous motion and they collide with each other. liquid molecules when they collide, they tend to transfer the energy to colliding molecule, when the same collisions happens with the liquid molecules on the surface, and if enough amount of energy transferred to them is able to overcome the intermolecular attractive forces, it leads the molecule to escape into gas phase. This process is called evaporation.

Factors affecting evaporation:
1) Temperature: Since the kinetic energy of the moving molecules is directly related to the temperature. As the temperature increases the kinetic energy of the liquid molecules also increases, which further increases the collisions leading to more number of liquid molecules to escape from the liquid phase to gas phase.
2) Concentration of the molecules under consideration in the air: For example if we take the some amount of liquid in the enclosed container, in the beginning there will be no molecules evaporated as the time proceeds the molecules on the surface which have enough energy to overcome the intermolecular attraction forces will start to evaporate, and the number of molecules in the gas phase increases. At a certain point of time the molecules tend to return back to the liquid phase. This occurs when the equilibrium is reached. At this time the gas phase is said to be saturated.
3) Substance dissolved in it: More the amount of dissolved salts less the evaporation.
4) Pressure: When there is more pressure outside the liquid phase, more energy is needed for the liquid molecules on the surface to escape into the gas phase.
5) Surface area: More the surface area exposed more is the evaporation

Note: Evaporation is an important process in the water cycle. In nature solar energy drives evaporation. Transpiration in plants is also an example of evaporation. Transpiration is called vital evil, evil because it drains the water from plants, vital because without transpiration there will be excess water in the plant leading to plant death.