Question

What are the two types of vaporization?

Answer 1

Hint: Vaporization is the process in which liquid turns into gas. The two types of vaporization are boiling and evaporation. One key difference between the two types of vaporization is that evaporation is a surface phenomenon, while boiling is a bulk phenomenon.

Complete answer:
Vaporization is the process of change in state of a substance from liquid to vapour. For vaporization to occur, heat must be supplied to the liquid system, in order for the cohesive forces of the liquid particles to be broken. Once this happens, the particles escape into the atmosphere and exist in vapour state. The heat that a system requires in order to undergo vaporization is called heat of vaporization, and this is either obtained from the surroundings, or it is supplied by the system itself once its temperature is lowered and it releases heat. The heat of vaporization is a direct measure of the cohesive forces that exist between the liquid molecules. The process of vaporization has been identified to be of two different types: evaporation and boiling.
 Evaporation is a phase transition from liquid to vapour phase, where it occurs at temperature below boiling temperature at a given pressure. The process of evaporation is seen to happen on the surface of the liquid, where only the surface particles escape into vapour phase. Specifically, the occurrence of evaporation is when the partial pressure of vapour of a substance is less than the equilibrium vapour pressure.
Boiling, on the other hand, occurs at the bulk of the liquid, or rather, below the surface. It is also a phase transition from liquid to vapour phase, where the vapour forms bubbles under the liquid surface. Boiling occurs when the equilibrium vapour pressure of the substance is greater than or equal to the environmental pressure. The temperature at which a liquid boils is called its boiling point, and as we know, each liquid has its own specific value for boiling point. As the pressure of the environment changes, a change is seen in the boiling point as well.

Note:
A key point to note is that although evaporation and boiling are phase transitions from liquid to vapour phase, there are differences in the kind of the particles involved in the process: in evaporation, the surface particles are involved, while in boiling, the particles below the surface are involved. However, both processes only occur when heat requirements are met.