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While the term chemical substance is a precise technical term that is synonymous with chemical for chemists, the word chemical is used in general usage to refer to both (pure) chemical substances and mixtures (often called compounds), [14] and especially when produced or purified in a laboratory or an industrial process.
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chemical substance. Also pure substance or simply substance. A form of matter that has constant chemical composition and characteristic properties and which cannot be separated into simpler components by purely physical methods (i.e. without breaking chemical bonds). It is often called a pure substance to distinguish it from a mixture. chemical ...
[8] [9] Mixtures differ from chemical compounds in the following ways: The substances in a mixture can be separated using physical methods such as filtration, freezing, and distillation. There is little or no energy change when a mixture forms (see Enthalpy of mixing). The substances in a mixture keep their separate properties.
Many solid chemical substances—for example many silicate minerals—are chemical substances, but do not have simple formulae reflecting chemically bonding of elements to one another in fixed ratios; even so, these crystalline substances are often called "non-stoichiometric compounds".
If a mixture is separated to isolate one chemical substance to a desired degree, the resulting substance is said to be chemically pure. [16] Chemical substances can exist in several different physical states or phases (e.g. solids, liquids, gases, or plasma) without changing their chemical composition.
At last count 96/97 of the 97 elements (hydrogen through einsteinium, except astatine and francium) isolated in pure form and in macroscopic quantities have images.; There are few images of very low encyclopedic quality for which it should be relatively easy to obtain higher quality: Ca.
In a fluid mixture like a petroleum gas or oil there are lots of molecule types, and within this mixture there are families of molecule types (i.e. groups of fluid components). The simplest group is the n-alkanes which are long chains of CH 2-elements. The more CH 2-elements, or carbon atoms, the longer molecule. Critical viscosity and critical ...