Write one similarity between physisorption and chemisorption.

Hint: Try to recall adsorption, which is defined as phenomena in which deposition of molecular species on any surface takes place and also, they are exothermic in nature.

Complete step by step solution:
Adsorption is defined as “the phenomenon of deposition of higher concentration of any molecular species on any surface in comparison to the bulk phases”. The substance on the surface of which adsorption takes place is called adsorbent and the molecular species which gets adsorbed is termed as adsorbate.
There are many factors on the basis of which different types of adsorption are classified. But here we will only see types of adsorption on the basis of forces existing between adsorbate molecule and adsorbent. They are:
Physisorption-
1. This type of adsorption is also known as physical adsorption or Vander Waals adsorption due to the presence of Vander Waals force of attraction between adsorbate and adsorbent.
2. It has low heat of adsorption.
3. It is a reversible process.
4. It forms multilayers of adsorbed molecules on adsorbent surfaces.
5. It is not very specific i.e. does not depend on the type of gas adsorbed.
6. It is an exothermic reaction due to release of energy after adsorption of molecules.

Chemisorption-
1. This type of adsorption is also known as chemical adsorption due to the formation of chemical bonds between adsorbate and adsorbent.
2. It has high heat of adsorption.
3. It is an irreversible process.
4. It forms monomolecular layers on the adsorbent surface.
5. It is highly specific.
6. It is also exothermic in nature.

Therefore, after discussion of the points it is quite clear that the one similarity between physisorption and chemisorption is that both are exothermic in nature.

Note: There are several examples of adsorption which we see in our everyday life. For example: Adsorption of water vapors on silica gel which is done to reduce humidity.