Read the given passage and answers following question:
Factors that influence the adsorption of a gas on a solid
1. Nature and surface area of adsorbent : Greater the surface area of the adsorbent, greater is the volume of gas adsorbed. Due to this reason, substances like charcoal and silica gel are best adsorbents because they have high surface area and highly porous structure.
2. Temperature : It is observed that the adsorption decreases with the increase of temperature.
For example, one gram of charcoal adsorbs about 10 ml of `N_2` at 273 K, 20 ml at 244 K and 45 ml at 195 K.
3. Pressure : At constant temperature, the adsorption of gas increases with the increase of pressure.
At low temperature, the adsorption of gas increases very rapidly as the pressure is increased.
4. Activation of the solid adsorbent.
Answer the following question :
What is adsorption ?

Explanation

The process of adhesion of molecule of liquid or gases (adsorbate) onto the surface of a solid particle(adsorbent).