Question

The process of converting gas into liquid on cooling is called:
(A) Evaporation
(B) Condensation
(C) Diffusion
(D) Sublimation

Answer 1

Hint: In Sublimation and Evaporation, the density of the substance increases at the end of the reaction. In Condensation, the density of the compound increases at the end of the reaction. In diffusion, we cannot predict the density change of the compound at the end of the process.

Complete answer:
The process of converting the gaseous form of any substance to its liquid form upon cooling is called condensation.
- Thus, we can say that as we cool any gas up to certain temperatures, it is possible to convert it into liquid which is called condensation of the gas.
As an example, we can see some water droplets on the bottle which is just taken out of the refrigerator. These droplets are the result of condensation of the water molecules present in the air in the form of moisture. They get converted into liquid state as they get closer to the cool bottle.
- Evaporation is the inverse process of condensation in which liquid gets converted into gaseous form upon heating. So, option (A) is not correct.
- Diffusion process does not involve change in the physical state of the substance. So, it is also not a correct answer.
- Sublimation is a process in which a solid is directly converted to its gaseous form. So, option (D) also cannot be a correct answer.

Therefore, we can conclude that option (B) is a correct answer.

Note:
Remember that when liquid gets converted into gaseous form, the process is called evaporation and when a gas is converted into its liquid form upon cooling, the process is called condensation. Remember that this condensation process is different from the condensation reaction (Organic chemistry reaction) which involves removal of a small molecule when two compounds react.