Title: change of a quantity
Long Title: IUPAC Gold Book - change of a quantity
DOI: 10.1351/goldbook.C00968
Status: current

Definition
The increment of the value of a quantity \(Q\) with time. The change may be expressed either infinitesimally at time \(t\) by the differential \(\rm{d}Q\) or \(\rm{d}Q(t)\), or in practice it may be expressed by a finite increment over the time interval \((t_{1};t_{2})\), i.e. \(Q(t_{2})- Q(t_{1})\), which may be written \(\Delta Q\) or \(\Delta Q(t_{1};t_{2})\) \[\Delta Q = \Delta Q(t_{1};t_{2}) = Q(t_{2})- Q(t_{1})\] Examples are: mass change, \(\Delta m\); amount of substance change, \(\Delta n\); volume change, \(\Delta V\); substance concentration change, \(\Delta c\).

Related Terms
- amount of substance: https://goldbook.iupac.org//terms/view/A00297
- substance concentration: https://goldbook.iupac.org//terms/view/S06072

Source
- PAC, 1992, 64, 1569. 'Quantities and units for metabolic processes as a function of time (IUPAC Recommendations 1992)' on page 1571 (https://doi.org/10.1351/pac199264101569)

Other Outputs
- html: https://goldbook.iupac.org/terms/view/C00968/html
- json: https://goldbook.iupac.org/terms/view/C00968/json
- xml: https://goldbook.iupac.org/terms/view/C00968/xml

Citation: Citation: 'change of a quantity' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. 10.1351/goldbook.C00968
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Accessed: 2025-10-29T05:39:51+00:00