Matter of constant chemical composition and properties

Chemical substance

Chemical substance

A chemical substance is a form of <a href="/en/Matter" title="Matter" class="wl">matter</a> having constant <a href="/en/Chemical_composition" title="Chemical composition" class="wl">chemical composition</a> and characteristic properties.<a href="#cite_note-1" style="counter-reset: mw-Ref 1;">[1]</a><a href="#cite_note-2" style="counter-reset: mw-Ref 2;">[2]</a> Some references add that chemical substance cannot be separated into its constituent <a href="/en/Chemical_element" title="Chemical element" class="wl">elements</a> by physical separation methods, i.e., without breaking <a href="/en/Chemical_bond" title="Chemical bond" class="wl">chemical bonds</a>.<a href="#cite_note-3" style="counter-reset: mw-Ref 3;">[3]</a> Chemical substances can be simple substances (substances consisting of a single <a href="/en/Chemical_element" title="Chemical element" class="wl">chemical element</a>),<a href="#cite_note-Scerri-2005-4" style="counter-reset: mw-Ref 4;">[4]</a> <a href="/en/Chemical_compound" title="Chemical compound" class="wl">chemical compounds</a>, or <a href="/en/Alloy" title="Alloy" class="wl">alloys</a>.

<div class="shortdescription nomobile noexcerpt noprint searchaux" style="display:none" about="#mwt1">Matter of constant chemical composition and properties</div>
<style data-mw-deduplicate="TemplateStyles:r1033289096" typeof="mw:Extension/templatestyles mw:Transclusion">.mw-parser-output .hatnote{font-style:italic}.mw-parser-output div.hatnote{padding-left:1.6em;margin-bottom:0.5em}.mw-parser-output .hatnote i{font-style:normal}.mw-parser-output .hatnote+link+.hatnote{margin-top:-0.5em}</style>
<figure class="mw-default-size wiki-thumb"><a href="/en/File:Kochendes_wasser02.jpg" class="mw-file-description image media-thumb" data-hash="File:Kochendes_wasser02.jpg"><img loading="lazy" src="//upload.wikimedia.org/wikipedia/commons/thumb/1/18/Kochendes_wasser02.jpg/220px-Kochendes_wasser02.jpg" decoding="async" data-file-width="674" data-file-height="644" data-file-type="bitmap" height="210" width="220" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/1/18/Kochendes_wasser02.jpg/330px-Kochendes_wasser02.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/1/18/Kochendes_wasser02.jpg/440px-Kochendes_wasser02.jpg 2x" alt="Kochendes_wasser02.jpg"></a><figcaption>Steam and liquid water are two different forms of the same chemical (pure) substance: water.</figcaption></figure>

Chemical substances are often called 'pure' to set them apart from <a href="/en/Mixture" title="Mixture" class="wl">mixtures</a>. A common example of a chemical substance is pure <a href="/en/Water_(molecule)" title="Water (molecule)" class="mw-redirect wl">water</a>; it has the same properties and the same <a href="/en/Atomic_ratio" title="Atomic ratio" class="wl">ratio</a> of <a href="/en/Hydrogen" title="Hydrogen" class="wl">hydrogen</a> to <a href="/en/Oxygen" title="Oxygen" class="wl">oxygen</a> whether it is isolated from a river or made in a <a href="/en/Laboratory" title="Laboratory" class="wl">laboratory</a>. Other chemical substances commonly encountered in pure form are <a href="/en/Diamond" title="Diamond" class="wl">diamond</a> (carbon), <a href="/en/Gold" title="Gold" class="wl">gold</a>, <a href="/en/Edible_salt" title="Edible salt" class="mw-redirect wl">table salt</a> (<a href="/en/Sodium_chloride" title="Sodium chloride" class="wl">sodium chloride</a>) and refined <a href="/en/Sugar" title="Sugar" class="wl">sugar</a> (<a href="/en/Sucrose" title="Sucrose" class="wl">sucrose</a>). 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 <a href="/en/Solid" title="Solid" class="wl">solids</a>, <a href="/en/Liquid" title="Liquid" class="wl">liquids</a>, <a href="/en/Gas" title="Gas" class="wl">gases</a>, or <a href="/en/Plasma_(physics)" title="Plasma (physics)" class="wl">plasma</a>, and may change between these <a href="/en/Phases_of_matter" title="Phases of matter" class="mw-redirect wl">phases of matter</a> with changes in <a href="/en/Temperature" title="Temperature" class="wl">temperature</a> or <a href="/en/Pressure" title="Pressure" class="wl">pressure</a> and <a href="/en/Time" title="Time" class="wl">time</a>. Chemical substances may be combined or converted to others by means of <a href="/en/Chemical_reaction" title="Chemical reaction" class="wl">chemical reactions</a>.

A chemical substance is a form of matter having constant chemical composition and characteristic properties. 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 , gold, table salt and refined sugar . 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. 