Read the given passage and answers following questions :
There are mainly two type of adsorption of gases on solids. If accumulation of gases on the surface of solid occurs on account of weak vander Waal forces, the adsorption is termed as physical adsorption. When gas molecules or atoms held to solid surface by chemical bonds, adsorption is termed as chemical adsorption. The chemical bonds may be covalent or ionic. Chemical adsorption involves a high energy of activation therefore it is referred as Activated adsorption. A physical adsorption at low temperature may pass into chemical adsorption temperature is increased.
What type of activation energy in physical adsorption ?