Chemistry is the science of the substances and their transformations that result from some substances are obtained other substances with new properties.
From the point of view of the atomic-molecular theory of the substance composition chemical transformations (reaction) are due to the rearrangement of atoms in molecules reacting substances, resulting from some other molecules with different composition and internal structure.
Chemistry is divided into several major sections representing independent chemical discipline, mutually connected to each other. Inorganic chemistry and organic chemistry have as its object the study of composition and properties of inorganic and organic substances, respectively. The latter include the substances, containing in the structure a chemical element carbon. Many of these substances are proteins (see), fats (see), nucleic acid (see), carbohydrates (see) - are indispensable components of organisms. The problems of chemistry of biologically important substances and their transformations in the organisms involved in biological chemistry. (see Biochemistry). Physical chemistry deals with the study of mutual relation of physical and chemical phenomena, analytical chemistry methods to determine the qualitative and quantitative composition of substances and their mixtures. The subject of hydrochemistry is the study of the chemical composition of natural waters, and the subject of histochemistry - the study of localization of chemical and biochemical reactions in cells and tissues. Theories of chemistry and chemical methods of research are widely used in biology, physiology and medicine.
Cm. Nuclear chemistry.