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  2. Chemical substance - Wikipedia

    en.wikipedia.org/wiki/Chemical_substance

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

  3. Molecule - Wikipedia

    en.wikipedia.org/wiki/Molecule

    A compound's empirical formula is a very simple type of chemical formula. [27] It is the simplest integer ratio of the chemical elements that constitute it. [28] For example, water is always composed of a 2:1 ratio of hydrogen to oxygen atoms, and ethanol (ethyl alcohol) is

  4. Chemical compound - Wikipedia

    en.wikipedia.org/wiki/Chemical_compound

    [16] [17] [18] A molecule may be homonuclear, that is, it consists of atoms of one chemical element, as with two atoms in the oxygen molecule (O 2); or it may be heteronuclear, a chemical compound composed of more than one element, as with water (two hydrogen atoms and one oxygen atom; H 2 O). A molecule is the smallest unit of a substance that ...

  5. Glossary of chemistry terms - Wikipedia

    en.wikipedia.org/wiki/Glossary_of_chemistry_terms

    Also acid ionization constant or acidity constant. A quantitative measure of the strength of an acid in solution expressed as an equilibrium constant for a chemical dissociation reaction in the context of acid-base reactions. It is often given as its base-10 cologarithm, p K a. acid–base extraction A chemical reaction in which chemical species are separated from other acids and bases. acid ...

  6. Water - Wikipedia

    en.wikipedia.org/wiki/Water

    Water is an inorganic compound with the chemical formula H 2 O.It is a transparent, tasteless, odorless, [c] and nearly colorless chemical substance.It is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as a solvent [20]).

  7. Matter - Wikipedia

    en.wikipedia.org/wiki/Matter

    Steam and liquid water are two different forms of the same pure chemical substance, water. A chemical substance is a unique form of matter with constant chemical composition and characteristic properties. [13] [14] Chemical substances may take the form of a single element or chemical compounds.

  8. Activity coefficient - Wikipedia

    en.wikipedia.org/wiki/Activity_coefficient

    In other words: The compound shows nonideal behavior in the dilute case. The above definition of the activity coefficient is impractical if the compound does not exist as a pure liquid. This is often the case for electrolytes or biochemical compounds. In such cases, a different definition is used that considers infinite dilution as the ideal state:

  9. Liquid - Wikipedia

    en.wikipedia.org/wiki/Liquid

    A liquid is a nearly incompressible fluid that conforms to the shape of its container but retains a nearly constant volume independent of pressure. It is one of the four fundamental states of matter (the others being solid, gas, and plasma), and is the only state with a definite volume but no fixed shape.