Chemistry Chemistry is a department of science that concerns with the properties of matter, i.e. the physical properties and chemical reactions of matter. Chemists are particularly interested with the properties of pure substances; free from other impurities as much as possible. Therefore, chemists are often well equipped with separation and analytical techniques. Theories and compedium of reactions in chemistry are generally divided into three branches, namely, inorganic chemistry, organic chemistry, and physical chemistry. The theory and laboratory skills for separation and analysis of inorganic or organic compounds is learned under analytical chemistry.