chem·is·try (kèm¹-strê) noun

1. The science of the composition, structure, properties, and reactions of matter, especially of atomic and molecular systems.

2. The composition, structure, properties, and reactions of a substance.

INORGANIC CHEMISTRY deals mainly with components of mineral origin. ORGANIC CHEMISTRY was first defined as the study of substances produced by living organisms; it is now defined as the study of the compounds of CARBON. PHYSICAL CHEMISTRY is concerned with the physical properties of materials; its subcategories are ELECTROCHEMISTRY; thermochemistry, the investigation of the changes in energy and ENTROPY that occur during chemical reactions and phase transformations (see states of matter); and chemical kinetics, which is concerned with the details of chemical reactions and of how equilibrium is reached between the products and reactants. Analytical chemistry is a collection of techniques that allows exact laboratory determination of the chemical composition of a given sample of material.