amount of substance concentration

Amount of substance concentration, often called simply concentration, is a quantitative measure of the number of atom s per unit volume in a sample of a matter . The matter might be in the solid, liquid, or gaseous state.

The standard unit of concentration is the mole per meter cubed (mol/m ³ or mol · m ^-3 ). One mole represents approximately 6.022169 x 10 ²³ particles, usually atoms. Alternatively, concentration can be expressed in moles per centimeter cubed (mol/cm ³ or mol · cm ^-3 ). To convert from mol/m ³ to mol/cm ³ , multiply by 10 ^-6 (0.000001). Conversely, multiply by 10 ⁶ (1,000,000).

For a sample of a specific pure elemental substance, the concentration is directly proportional to the density . However, concentration is not proportional to density in general. Consider a cubic meter of space containing one mole of hydrogen atoms. This is about 1/16 the density of a cubic meter of space containing one mole of oxygen atoms, because the mass of an oxygen atom is approximately 16 times the mass of a hydrogen atom. This is true even though the amount-of-substance concentrations of the two parcels are identical.

Also see amount of substance , density , meter cubed , mole , SI (International System of Units), and Table of Physical Units .

Last updated on: Sep 21, 2005

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