Question

Evaporation of a liquid at room temperature leads to ______ on the liquid surface.
(A) heating
(B) cooling
(C) vapors
(D) precipitation

Answer 1

Hint: To solve this question we first need to understand the concept of thermal and kinetic energy. When a system or a body absorbs heat due to the motion of the subatomic particles like atoms, molecules, or ions in the system or the body, the energy gained is known as thermal energy. The net amount of thermal energy of the system is known as heat.
Thermal energy is also the total internal energy of an object due to the random motion of its subatomic particles.

Complete answer:
First, let us understand what evaporation is. When a liquid substance converts into a gaseous state upon absorbing energy the process is known as evaporation. It is a process of change of state of matter.
The molecules at the surface of a liquid that has a temperature higher than the room temperature possess the maximum kinetic energy. Due to this kinetic energy, the particles overcome intermolecular forces and evaporate i.e., escape the liquid surface.
As these fast-moving particles having high kinetic energy escape, the temperature of the liquid is decreased and the liquid cools down to room temperature. This process is known as convection.
So, we can say that evaporation of a liquid at room temperature leads to cooling on the liquid surface.

Hence, option (B) cooling is correct.

Note:
It should be noted that the most common example of cooling due to evaporation is sweat. When we sweat or perspiration, the heat of the body is absorbed, and the perspiration evaporates. This causes the body to cool down.