Question

Which of the following is a surface phenomenon?
A. Boiling
B. Evaporation
C. Dilution
D. None of the above

Answer 1

Hint: Surface phenomenon is mainly the study of science of interfaces. The interfaces can be interfaces of solid, liquid and gases. Check the definitions and differences between the terms to get the correct answer. The process which occurs on the surface of the liquid only is a surface phenomenon.

Complete step by step answer:
Let us discuss the options one-by-one to get the correct answer:
We will discuss boiling and evaporation together and check their differences and dilution is not related to these terms, so we will discuss it later.
- The differences between Boiling and Evaporation are:

EVAPORATION	BOILING
Evaporation is a faster process than boiling.	Boiling is a slow process.
Evaporation process can occur at fixed temperature only.	Boiling process can occur at any temperature.
The temperature of the liquid decreases in this process.	The temperature of the liquid or body remains constant in this process.
Only takes place throughout the liquid.	The process only takes place on the surface of the liquid.
The process continues until the air above the surface of liquid is unsaturated.	The process continues until external temperature and internal temperature of the liquid are equal.
It is a surface phenomenon. Only molecules on the surface get sufficient amounts of energy which helps in overcoming the forces of attraction and gets converted to water vapours.	It is a bulk phenomenon. This is because all the molecules present in the liquid are heated up and get energy.
Heat energy is needed to start this process.	Sunlight is one of the major sources of this process.

C. Dilution: It is the process in which concentration of solute in a solution is decreased by adding solvent in excess in the solution without adding solute further. This process is also a bulk phenomenon. This is because the volume of solution increases in the whole solution.

Evaporation is a surface phenomenon, which is option ‘b’.

Note: Surface phenomenon also comes under adsorption. This is actually the adhesion between the substances on the solids and liquids surfaces. Some examples are silica gel, gases get adsorbed on the surface of carbon and any metallic surface.