In modern warfare, chemical weapons were first used in World War I (1914–18). Like nuclear and biological weapons, chemical weapons are often classified as weapons of mass destruction.

Chemical compounds are made up of atoms of different elements, joined together by chemical bonds. A chemical synthesis usually involves the breaking of existing bonds and the formation of new ones.

Chemical equilibrium is the condition in the course of a reversible chemical reaction in which no net change in the amounts of reactants and products occurs. A reversible chemical reaction is one in …

Chemical formula, any of several kinds of expressions of the composition or structure of chemical compounds. The forms commonly encountered are empirical, molecular, structural, and projection …

Mar 2, 2026 · Cooking, fermentation, glass making, and metallurgy are all chemical processes that date from the beginnings of civilization. Today, vinyl, Teflon, liquid crystals, semiconductors, and …

Feb 19, 2026 · A chemical element is any substance that cannot be decomposed into simpler substances by ordinary chemical processes. Elements are the fundamental materials of which all …

CHEMICAL meaning: 1 : of or relating to chemistry; 2 : working by means of chemicals

Jan 13, 2026 · Substances are either chemical elements or compounds. A chemical reaction rearranges the constituent atoms of the reactants to create different substances as products.

The chemical energy in food is converted by the body into mechanical energy and heat. The chemical energy in coal is converted into electrical energy at a power plant.

Feb 20, 2026 · Professor and Associate Head, Department of Chemistry, University of Illinois at Urbana-Champaign. Author of Chemical Principles and many others.