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  1. Chemical reaction | Definition, Equations, Examples, & Types - Britannica

    Nov 30, 2025 · A chemical reaction is a process in which one or more substances, the reactants, are converted to one or more different substances, the products. Substances are either chemical …

  2. Chemical compound | Definition, Examples, & Types | Britannica

    Nov 11, 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.

  3. Chemistry | Definition, Topics, Types, History, & Facts | Britannica

    Nov 8, 2025 · The identification of pure substances and the analysis of chemical mixtures enable all other chemical disciplines to flourish. The importance of analytical chemistry has never been greater …

  4. Chemical energy | Definition & Facts | Britannica

    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. The chemical energy in a battery …

  5. Chemical formula | Definition, Types, Examples, & Facts | Britannica

    Nov 1, 2025 · 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 …

  6. Chemical kinetics | Definition, Equations, & Facts | Britannica

    The detailed mechanism by which a chemical process occurs is referred to as the reaction path, or pathway. The vast amount of work done in chemical kinetics has led to the conclusion that some …

  7. Chemical Definition & Meaning | Britannica Dictionary

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

  8. Chemical element | Definition, Origins, Distribution, & Facts - Britannica

    Nov 29, 2025 · 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 …

  9. chemistry - Kids | Britannica Kids | Homework Help

    In 1661 a British scientist named Robert Boyle described chemical elements as simple, basic substances. In the 1770s a French chemist named Antoine Lavoisier helped to explain chemical …

  10. Melamine | Industrial, Food & Medical Applications | Britannica

    Oct 17, 2025 · Evidence of misuse of the chemical in China emerged in 2007, when more than 4,000 dogs and cats in the United States died from kidney failure as a result of ingesting melamine-tainted …