ABSTRACT
This chapter deals with various chemical and physical processes that at first sight appear unrelated but which have features in common. In particular, the chemical potential plays a key role in the discussion of all the phenomena that are considered. The adsorption of molecules on a surface in contact with a gas can take place either via a process called chemical adsorption or through a different process termed physical adsorption. Chemical adsorption involves the formation of chemical bonds at the surface giving rise to a relatively immobile layer that cannot be removed simply by lowering the gas pressure. Chemical adsorption involves the formation of chemical bonds at the surface giving rise to a relatively immobile layer that cannot be removed simply by lowering the gas pressure. In contrast, physical adsorption involves weaker surface interactions, and the number of physically adsorbed molecules, at a given temperature, does depend on the gas pressure.
