The amount of substance, n, of a sample or system is a physical quantity which is proportional to the number of elementary entities present. "Elementary entities" may be atoms, molecules, ions, electrons, or particles, the choice of which is dependent upon context and must be stated. Amount of substance is sometimes referred to as chemical amount or, incorrectly, as number of moles.^[1] A physical quantity is either a quantity within physics that can be measured (e. ... The word proportionality may have one of a number of meanings: In mathematics, proportionality is a mathematical relation between two quantities. ... In particle physics, an elementary particle is a particle of which other, larger particles are composed. ...

The SI unit for amount of substance is the mole (mol), which is defined as the amount of substance that has an equal number of elementary entities as there are atoms in 0.012 kg (or 12 g) of carbon-12. That number is the Avogadro constant, N_A, which has a value^[2] of 6.02214179(30)×10²³ mol⁻¹. Look up si, Si, SI in Wiktionary, the free dictionary. ... The mole (symbol: mol) is the SI base unit that measures an amount of substance. ... Shown above is a computer-generated image of the International Prototype Kilogram (“IPK”). The IPK is the kilogram. ... BIC pen cap, about 1 gram. ... For other uses, see Carbon (disambiguation). ... The Avogadro constant (symbols: L, NA), also called the Avogadro number and, in German scientific literature, sometimes also known as the Loschmidt constant/number, is formally defined to be the number of entities in one mole,[1][2] that is the number of carbon-12 atoms in 12 grams (0. ...

Terminology

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When quoting an amount of substance, it is necessary to specify the entity involved (unless there is no risk of ambiguity). One mole of chlorine could refer either to chlorine atoms (as in 58.44 g of sodium chloride) or to chlorine molecules (as in 22.711 dm³ of chlorine gas at STP). The simplest way to avoid ambiguity is to replace the term "substance" by the name of the entity and/or to quote the empirical formula. For example: Wikipedia does not have an article with this exact name. ... Wiktionary (a portmanteau of wiki and dictionary) is a multilingual, Web-based project to create a free content dictionary, available in over 150 languages. ... General Name, symbol, number chlorine, Cl, 17 Chemical series halogens Group, period, block 17, 3, p Appearance yellowish green Standard atomic weight 35. ... Sodium chloride, also known as common salt, table salt, or halite, is a chemical compound with the formula NaCl. ... The Three-Letter Acronym STP can have several meanings: Straight Through Processing is a banking term where a financial transaction is automatically completed without manual intervention. ... In chemistry, the empirical formula of a chemical compound is a simple expression of the relative number of each type of atom (called a chemical element) in it. ...

amount of chloroform, CHCl₃

amount of sodium, Na

amount of hydrogen (atoms), H

n(C₂H₄)

This can be considered to be a technical definition of the word "amount", a usage which is also found in the names of certain derived quantities (see below). R-phrases , , , S-phrases , Flash point Non-flammable U.S. Permissible exposure limit (PEL) 50 ppm (240 mg/m3) (OSHA) Supplementary data page Structure and properties n, εr, etc. ... For sodium in the diet, see Edible salt. ... General Name, Symbol, Number hydrogen, H, 1 Chemical series nonmetals Group, Period, Block 1, 1, s Appearance colorless Atomic mass 1. ... Ethylene (or IUPAC name ethene) is the chemical compound with the formula C2H4. ...

Derived quantities

When amount of substance enters into a derived quantity, it is usually as the denominator: such quantities are known as "molar quantities".^[3] For example, the quantity which describes the volume occupied by a given amount of substance is called the molar volume, while the quantity which describes the mass of a given amount of substance is the molar mass. Molar quantities are sometimes denoted by a subscript latin "m" in the symbol,^[3] e.g. C_p,m, molar heat capacity at constant pressure: the subscript may be omitted if there is no risk of ambiguity, as is often the case in pure chemistry. In chemistry, the molar volume of a substance is the ratio of the volume of a sample of that substance to the amount of substance (usually in mole) in the sample. ... This article does not cite any references or sources. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... For other uses, see Chemistry (disambiguation). ...

The main derived quantity in which amount of substance enters into the numerator is amount of substance concentration, c. This name is often abbreviated to "amount concentration",^[4] except in clinical chemistry where "substance concentration" is the preferred term^[5] (to avoid any possible ambiguity with mass concentration). The name "molar concentration" is incorrect,^[6] if commonly used. Clinical chemistry (also known as clinical biochemistry, chemical pathology or pure blood chemistry) is the area of pathology that is generally concerned with analysis of bodily fluids. ... A mass concentration or mascon is a region of a planet or moons crust that contains a large amount of material that is denser than average for that body. ...

See also

• Amount fraction, x

References

• Bureau International des Poids et Mesures (2006). The International System of Units (SI) (8th Edn). ISBN 92-822-2213-6. pp. 114–15.
• International Union of Pure and Applied Chemistry. "amount of substance, n". Compendium of Chemical Terminology Internet edition.
• International Union of Pure and Applied Chemistry (1993). Quantities, Units and Symbols in Physical Chemistry (2nd Edn). Oxford: Blackwell Science. ISBN 0-632-03583-8. p. 46. Electronic version.

1. ^ To use "number of moles" to refer to amount of substance is no more correct than to use "number of seconds" to refer to time. The amount of substance is the same whatever unit is used to measure it.
2. ^ International Council of Science Committee on Data for Science and Technology (2007). 2006 CODATA recommended values.
3. ^ ^{a b} International Union of Pure and Applied Chemistry (1993). Quantities, Units and Symbols in Physical Chemistry (2nd Edn). Oxford: Blackwell Science. ISBN 0-632-03583-8. p. 7. Electronic version.
4. ^ International Union of Pure and Applied Chemistry. "amount-of-substance concentration". Compendium of Chemical Terminology Internet edition.
5. ^ International Union of Pure and Applied Chemistry (1996). "Glossary of Terms in Quantities and Units in Clinical Chemistry." Pure Appl. Chem. 68:957–1000.
6. ^ "Molar concentration" should refer to a concentration per mole, i.e. an amount fraction. The use of "[[molar (unit)|]]" as a unit, equal to 1 mol/dm³, symbol M, is frequent, but not (as of May 2007) completely condoned by IUPAC: See International Union of Pure and Applied Chemistry (1993). Quantities, Units and Symbols in Physical Chemistry (2nd Edn). Oxford: Blackwell Science. ISBN 0-632-03583-8. p. 42 (n. 15). Electronic version.