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Steam and liquid water are two different forms of the same chemical substance, water.

A chemical substance is a form of matter that has constant chemical composition and characteristic properties.<ref>IUPAC, Compendium of Chemical Terminology, 2nd ed. (the "Gold Book") (1997). Online corrected version:  (2006–) "Chemical Substance".</ref> It cannot be separated into components by physical separation methods, i.e., without breaking chemical bonds. Chemical substances can be chemical elements, chemical compounds, ions 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. Chemical reactions convert one chemical substance into another.

Forms of energy, such as light and heat, are not considered to be matter, and thus they are not "substances" in this regard.


Chemical substance sections
Intro  Definition  History  Chemical elements  Chemical compounds  Substances versus mixtures  Chemicals versus chemical substances  Naming and indexing  Isolation, purification, characterization, and identification  See also  Notes and references  External links  

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Chemical::chemical    Compound::elements    Example::known    Which::sulfur    Element::mixture    Common::reaction

{{#invoke:redirect hatnote|redirect}}

Steam and liquid water are two different forms of the same chemical substance, water.

A chemical substance is a form of matter that has constant chemical composition and characteristic properties.<ref>IUPAC, Compendium of Chemical Terminology, 2nd ed. (the "Gold Book") (1997). Online corrected version:  (2006–) "Chemical Substance".</ref> It cannot be separated into components by physical separation methods, i.e., without breaking chemical bonds. Chemical substances can be chemical elements, chemical compounds, ions 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. Chemical reactions convert one chemical substance into another.

Forms of energy, such as light and heat, are not considered to be matter, and thus they are not "substances" in this regard.


Chemical substance sections
Intro  Definition  History  Chemical elements  Chemical compounds  Substances versus mixtures  Chemicals versus chemical substances  Naming and indexing  Isolation, purification, characterization, and identification  See also  Notes and references  External links  

PREVIOUS: IntroNEXT: Definition
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