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

    Nov 11, 2025 · 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 …

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

    Nov 8, 2025 · Chemistry is the science of the properties, composition, and structure of substances (defined as elements and compounds), the transformations they undergo, and the energy that is …

  3. 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 …

  4. 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 …

  5. Chemical energy | Definition & Facts | Britannica

    chemical energy, Energy stored in the bonds of chemical compounds. Chemical energy may be released during a chemical reaction, often in the form of heat; such reactions are called exothermic. …

  6. 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 …

  7. Chemical industry | Overview, Importance, & History | Britannica

    Dec 5, 2025 · Chemical industry, complex of processes, operations, and organizations engaged in the manufacture of chemicals and their derivatives. Raw materials include fossil fuels and inorganic …

  8. chemical reaction - Students | Britannica Kids | Homework Help

    A chemical reaction is a process in which one or more substances are converted to one or more different substances. In the reaction, the atoms of the starting substances are…

  9. Chemical change | Britannica

    Other articles where chemical change is discussed: chemical compound: …into their constituent elements by chemical changes. A chemical change (that is, a chemical reaction) is one in which the …

  10. Chemical bonding - Ionic, Covalent, Compounds | Britannica

    Oct 30, 2025 · Chemical bonding - Ionic, Covalent, Compounds: A second general feature of bonding also became apparent in the early days of chemistry. It was found that there are two large classes of …