Class 12 syllabus for Chemistry on Extramarks provides students with up to date information on the Chemistry Class 12 weightage. Students can access the Extramarks study material for the Chemistry syllabus of Class 12 CBSE. Since the new pattern for CBSE Class 12 Chemistry requires extensive hard work for students, the material is kept in a very systematic and organized way. Below are some of the topics that are included in the CBSE Class 12 Chemistry syllabus. This mechanism of attracting and retaining the molecules of a material by means of a solid (or liquid) on its surface resulting in a higher concentration of the molecules on the surface is known as adsorption. The substance that is adsorbed is called adsorbate, and the substance that adsorbs is called adsorbent. When the adsorption is retained on the surface by weak forces, the process is called direct adsorption or soft adsorption. This form of adsorption can be reversed by heating or by reducing the water. When the forces trapping the adsorbate on the surface are of the size of the chemical bonding forces, the process is called chemical adsorption or chemisorption. The process of adsorption is permanent. Adsorption is usually followed by heat evolution, i.e. it is an exothermic process. The degree of adsorption of a solid gas depends on the following factors: (a) nature of the adsorbate, (b) composition of the adsorbent, (c) temperature, and (d) pressure. The association or equation between the degree of the adsorption / m and the pressure P of the gas at a constant temperature is called the adsorption isotherm. A material that can affect the rate of a chemical reaction but stays chemically unchanged at the end is called a catalyst.