Chemistry | Definition, Topics, Types, History, Facts | Britannica Most of the materials that occur on Earth, such as wood, coal, minerals, or air, are mixtures of many different and distinct chemical substances Each pure chemical substance (e g , oxygen, iron, or water) has a characteristic set of properties that gives it its
Chemical compound | Definition, Examples, Types | Britannica Chemical compound, any substance composed of identical molecules consisting of atoms of two or more chemical elements All the matter in the universe is composed of the atoms of more than 100 different chemical elements, which are found both in pure form and combined in chemical compounds
Chemical weapon | History, Facts, Types, Effects | Britannica Chemical weapon, any of several chemical compounds, usually toxic agents, that are intended to kill, injure, or incapacitate In modern warfare, chemical weapons were first used in World War I (1914–18)
Properties, Uses, History of the Chemical Element - Britannica niobium (Nb), chemical element, refractory metal of Group 5 (Vb) of the periodic table, used in alloys, tools and dies, and superconductive magnets Niobium is closely associated with tantalum in ores and in properties
organic chemistry - Encyclopedia Britannica Organic chemistry, field of science concerned with the composition, properties, and structure of chemical elements and compounds that contain carbon atoms Carbon is unique in the variety and extent of structures that can result from the three-dimensional connections of its atoms
Chemical kinetics | Definition, Equations, Facts | Britannica Chemical kinetics, the branch of physical chemistry that is concerned with understanding how fast or how slow chemical reactions occur (that is, their rates) The principles of chemical kinetics apply to purely physical processes as well as to chemical reactions
Gold | Facts, Properties, Uses | Britannica Gold, a dense lustrous yellow precious metal and a chemical element of Group 11 Gold is attractive in color and brightness, durable to the point of virtual indestructibility, highly malleable, and usually found in nature in a comparatively pure form
Chemical dependency | Drug Abuse Treatment Options - Britannica chemical dependency, the body’s physical and or psychological addiction to a psychoactive (mind-altering) substance, such as narcotics, alcohol, or nicotine Physical dependency on such chemicals as prescription drugs or alcohol stems from repetitive use followed by the gradual increase in the body’s tolerance to, or ability to assimilate
Chemical equation | Balancing, Reactants, Products | Britannica Chemical equation, Method of writing the essential features of a chemical reaction using chemical symbols (or other agreed-upon abbreviations) By convention, reactants (present at the start) are on the left, products (present at the end) on the right