Chemical substance

Steam and liquid water are two different forms of the same chemical (pure) substance: water.

A chemical substance is a form of matter having constant chemical composition and characteristic properties.[1][2] Some references add that chemical substance cannot be separated into its constituent elements by physical separation methods, i.e., without breaking chemical bonds.[3] Chemical substances can be simple substances (substances consisting of a single chemical element),[4] chemical compounds, or alloys.

Chemical substances are often called 'pure' to set them apart from mixtures. A common example of a chemical substance is pure water; it has the same properties and the same ratio of hydrogen to oxygen whether it is isolated from a river or made in a laboratory. Other chemical substances commonly encountered in pure form are diamond (carbon), gold, table salt (sodium chloride) and refined sugar (sucrose). However, in practice, no substance is entirely pure, and chemical purity is specified according to the intended use of the chemical.

Chemical substances exist as solids, liquids, gases, or plasma, and may change between these phases of matter with changes in temperature or pressure and time. Chemical substances may be combined or converted to others by means of chemical reactions.

  1. ^ Hale, Bob (2013-09-19). Necessary Beings: An Essay on Ontology, Modality, and the Relations Between Them. OUP Oxford. ISBN 9780191648342. Archived from the original on 2018-01-13.
  2. ^ IUPAC, Compendium of Chemical Terminology, 2nd ed. (the "Gold Book") (1997). Online corrected version: (2006–) "Chemical Substance". doi:10.1351/goldbook.C01039
  3. ^ Hunter, Lawrence E. (2012-01-13). The Processes of Life: An Introduction to Molecular Biology. MIT Press. ISBN 9780262299947. Archived from the original on 2018-01-13.
  4. ^ Scerri, Eric (2005). "Simples and Compounds". Retrieved 15 May 2018.

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