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  2. Chemical substance - Wikipedia

    en.wikipedia.org/wiki/Chemical_substance

    A chemical substance is a unique form of matter with constant chemical composition and characteristic properties. [1][2] Chemical substances may take the form of a single element or chemical compounds. If two or more chemical substances can be combined without reacting, they may form a chemical mixture. [3]

  3. Characteristic property - Wikipedia

    en.wikipedia.org/wiki/Characteristic_property

    Characteristic property. A characteristic property is a chemical or physical property that helps identify and classify substances. The characteristic properties of a substance are always the same whether the sample being observed is large or small. Thus, conversely, if the property of a substance changes as the sample size changes, that ...

  4. List of purification methods in chemistry - Wikipedia

    en.wikipedia.org/wiki/List_of_purification...

    There are several type of distillation: simple distillation, steam distillation etc. Water purification combines a number of methods to produce potable or drinking water. Downstream processing refers to purification of chemicals, pharmaceuticals and food ingredients produced by fermentation or synthesized by plant and animal tissues, for ...

  5. Molecule - Wikipedia

    en.wikipedia.org/wiki/Molecule

    A pure substance is composed of molecules with the same average geometrical structure. The chemical formula and the structure of a molecule are the two important factors that determine its properties, particularly its reactivity. Isomers share a chemical formula but normally have very different properties because of their different structures.

  6. Chemical compound - Wikipedia

    en.wikipedia.org/wiki/Chemical_compound

    A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element is therefore not a compound. A compound can be transformed into a different substance by a chemical ...

  7. Chemical element - Wikipedia

    en.wikipedia.org/wiki/Chemical_element

    In chemistry, a pure element means a substance whose atoms all (or in practice almost all) have the same atomic number, or number of protons. Nuclear scientists, however, define a pure element as one that consists of only one isotope. [18] For example, a copper wire is 99.99% chemically pure if 99.99% of its atoms are copper, with 29 protons each.

  8. Separation process - Wikipedia

    en.wikipedia.org/wiki/Separation_process

    t. e. A separation process is a method that converts a mixture or a solution of chemical substances into two or more distinct product mixtures, [ 1 ] a scientific process of separating two or more substances in order to obtain purity. At least one product mixture from the separation is enriched in one or more of the source mixture's constituents.

  9. Standard state - Wikipedia

    en.wikipedia.org/wiki/Standard_state

    The standard state of a material (pure substance, mixture or solution) is a reference point used to calculate its properties under different conditions.A degree sign (°) or a superscript Plimsoll symbol (⦵) is used to designate a thermodynamic quantity in the standard state, such as change in enthalpy (ΔH°), change in entropy (ΔS°), or change in Gibbs free energy (ΔG°).