Surface chemistry is a branch in chemistry which deals with the study of the phenomenon occurring at the interface of two phases. The surface represents the physical boundary of any condensed phase like liquid or solid. It is the study of the chemical phenomena that occur at the interface of two surfaces which can be solid-liquid, solid-gas, solid-vacuum, liquid-gas, etc. It separates one phase from the other. Surface Chemistry Chapter deals with some essential features of surface chemistry such as adsorption, catalysis, and colloids which comprises emulsions and gels. After studying this chapter, students will be able to describe the interfacial phenomenon and its significance. Define adsorption and classify it into physical and chemical adsorption. Explain the mechanism of adsorption, explain the factors controlling adsorption from gases and solutions on solids. Explain adsorption results based on Freundlich adsorption isotherms; appreciate the role of catalysts in the industry; enumerate the nature of the colloidal state. Describe the preparation, properties, and purification of colloids; classify emulsions and describe their practice and properties; describe the phenomenon of gel formation; list the uses of colloids.