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In the natural sciences, including physiology and engineering, the qualifier specific or massic typically indicates an intensive quantity obtained by dividing an extensive quantity of interest by mass.[1][2] For example, specific leaf area is leaf area divided by leaf mass. Derived SI units involve reciprocal kilogram (kg−1), e.g., square metre per kilogram (m2⋅kg−1); the expression "per unit mass" is also often used.
In some fields, like acoustics, "specific" can mean division by a quantity other than mass.[1]
Named and unnamed specific quantities are given for the terms below.
List
[edit]Mass-specific quantities
[edit]Per unit of mass (short form of mass-specific):
- Specific absorption rate, power absorbed per unit mass of tissue at a given frequency
- Specific activity, radioactivity in becquerels per unit mass
- Specific energy, defined as energy per unit mass
- Specific internal energy, internal energy per unit mass
- Specific kinetic energy, kinetic energy of an object per unit of mass
- Specific enthalpy, enthalpy per unit mass
- Specific enzyme activity, activity per milligram of total protein
- Specific force, defined as the non-gravitational force per unit mass
- Specific heat capacity, heat capacity per unit mass, unless another unit is named, such as mole-specific heat capacity, or volume-specific heat capacity
- Specific latent heat, latent heat per unit mass
- Specific leaf area, leaf area per unit dry leaf mass
- Specific modulus, a materials property consisting of the elastic modulus per mass density of a material
- Specific orbital energy, orbital energy per unit mass
- Specific power, per unit of mass (or volume or area)
- Specific relative angular momentum, of two orbiting bodies is angular momentum divided by the reduced mass, or the cross product of the relative position and the relative velocity
- Specific surface area, per unit of mass, volume, or cross-sectional area
- Specific volume, volume per unit mass, i.e. the reciprocal of density
- Mass ratio, "ratio by mass", mass per unit mass, massic mass or specific mass: the ratio of two mass values (in kilogram per kilogram)
Examples of other uses
[edit]Per unit of other types.
- Brake-specific fuel consumption, fuel consumption per unit of braking power
- Thrust-specific fuel consumption, fuel consumption per unit of thrust
- Specific acid catalysis, in which the reaction rate is proportional to the concentration of the protonated solvent molecules
- Specific acoustic impedance, ratio of sound pressure to particle speed at a single frequency
- Specific capacity of a water well, quantity of water produced per (length) unit of drawdown
- Specific detectivity of a photodetector
- Specific gas constant, per molar mass
- Specific gravity, also called relative density, is a dimensionless quantity defined as the ratio of the density (mass divided by volume) of a substance to the density of a given reference material
- Specific humidity, mass of water vapour per unit mass dry air
- Specific impulse, impulse (momentum change) per unit mass of propellant
- Specific modulus, elastic modulus per mass density
- Specific speed, unitless figure of merit[clarification needed] used to classify pump impellers (pump-specific) and turbines (turbine-specific). Ratio of performance against reference pump that needs one unit of speed to pump one unit volume per one unit hydraulic head pressure. For a turbine, it is performance measured against a reference turbine that develops one unit of power per one unit speed per one unit of hydraulic head.
- Specific storage, specific yield, and specific capacity, quantify the capacity of an aquifer to release groundwater from storage per unit decline in hydraulic head pressure
- Specific strength, material strength (pressure required at failure) per unit material density
- Specific surface area, per unit of mass, volume, or cross-sectional area
- Specific thrust, thrust per unit mass of air intake rate
See also
[edit]References
[edit]- 1 2 "ISO 80000-1: Quantities and units – Part 1: General". iso.org. Retrieved 2023-10-16.
- ↑ Cohen, E. R.; et al. (2007). IUPAC Green Book (PDF) (3rd ed.). Cambridge: IUPAC and RSC Publishing. pp. 6 (20 of 250 in PDF file). ISBN 978-0-85404-433-7.