Dec 16, 2025 · 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.

Dec 26, 2025 · Cooking, fermentation, glass making, and metallurgy are all chemical processes that date from the beginnings of civilization. Today, vinyl, Teflon, liquid crystals, semiconductors, and …

Jan 10, 2026 · Professor and Associate Head, Department of Chemistry, University of Illinois at Urbana-Champaign. Author of Chemical Principles and many others.

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 …

5 days ago · gold (Au), chemical element, a dense lustrous yellow precious metal of Group 11 (Ib), Period 6, of the periodic table of the elements. Gold has several qualities that have made it …

Jan 8, 2026 · Caffeine, nitrogenous organic compound of the alkaloid group, substances that have marked physiological effects. Caffeine occurs in tea, coffee, guarana, maté, kola nuts, and cacao. …

Jan 9, 2026 · Cellular respiration, the process by which organisms combine oxygen with foodstuff molecules, diverting the chemical energy in these substances into life-sustaining activities and …

Dec 22, 2025 · Periodic table, in chemistry, is an organized array of all the chemical elements in order of increasing atomic number. When the elements are thus arranged, there is a recurring pattern in …

Dec 27, 2025 · Nitric oxide, colourless toxic gas that has important chemical signaling functions in animals and is a serious air pollutant.

Dec 29, 2025 · This article describes the molecular structure of water as well as its physical and chemical properties. For other major treatments of water, see climate; environmental works; …