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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 reaction | Definition, Equations, Examples, & Types - Britannica
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 elements or compounds. A chemical reaction rearranges the constituent atoms of the reactants to create different substances as products.
Chemical Definition & Meaning | Britannica Dictionary
CHEMICAL meaning: 1 : of or relating to chemistry; 2 : working by means of chemicals
Chemical element | Definition, Origins, Distribution, & Facts | Britannica
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 matter is composed. Learn more about the origins, distribution, and characteristics of chemical elements in this article.
Chemical formula | Definition, Types, Examples, & Facts | Britannica
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 formulas.
list of chemical elements - Encyclopedia Britannica
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 matter is composed. Here, the elements are ordered alphabetically.
chemical energy - Kids | Britannica Kids | Homework Help
Chemical energy is a form of potential energy that is in all substances. Food is the most important source of chemical energy for living things. The chemical energy in food is converted, or changed, by the body into moving mechanical energy and heat energy.
chemical reaction - Students | Britannica Kids | Homework Help
To describe chemical reactions, scientists use chemical equations, which make use of symbols and formulas for elements and compounds. The chemical equation for the reaction between sodium and water would be written as follows: 2 Na + 2 H 2 O → 2 NaOH + H 2
chemical element - Students | Britannica Kids | Homework Help
Any substance that cannot be decomposed into simpler substances by ordinary chemical processes is defined as a chemical element. Only 94 such substances are known to exist in nature (and two of them occur in only trace amounts).
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