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Air density, like air pressure, decreases with increasing altitude. It also changes with variations in atmospheric pressure, temperature and humidity. At 101.325 kPa (abs) and 20 °C (68 °F), air has a density of approximately 1.204 kg/m 3 (0.0752 lb/cu ft), according to the International Standard Atmosphere (ISA).
Specific gravity for liquids is nearly always measured with respect to water at its densest (at 4 °C or 39.2 °F); for gases, the reference is air at room temperature (20 °C or 68 °F). The term "relative density" (abbreviated r.d. or RD) is preferred in SI, whereas the term "specific gravity" is gradually being abandoned. [3]
at each geopotential altitude, where g is the standard acceleration of gravity, and R specific is the specific gas constant for dry air (287.0528J⋅kg −1 ⋅K −1). The solution is given by the barometric formula. Air density must be calculated in order to solve for the pressure, and is used in calculating dynamic pressure for moving vehicles.
Data obtained from Lange's Handbook of Chemistry, 10th ed. and CRC Handbook of Chemistry and Physics 44th ed. The annotation, d a °C/ b °C, indicates density of solution at temperature a divided by density of pure water at temperature b known as specific gravity. When temperature b is 4 °C, density of water is 0.999972 g/mL. % wt. methanol.
The specific weight, also known as the unit weight (symbol γ, the Greek letter gamma ), is a volume-specific quantity defined as the weight per unit volume of a material. A commonly used value is the specific weight of water on Earth at 4 °C (39 °F), which is 9.807 kilonewtons per cubic metre or 62.43 pounds-force per cubic foot.
Dimension. L 2 ⋅T −2 ⋅K −1. In thermodynamics, the specific heat capacity (symbol c) of a substance is the amount of heat that must be added to one unit of mass of the substance in order to cause an increase of one unit in temperature. It is also referred to as massic heat capacity or as the specific heat. More formally it is the heat ...
The table below displays densities and specific volumes for various common substances that may be useful. The values were recorded at standard temperature and pressure, which is defined as air at 0 °C (273.15 K, 32 °F) and 1 atm (101.325 kN/m 2 , 101.325 kPa, 14.7 psia, 0 psig, 30 in Hg, 760 torr).
Mass concentration, g/ (100 ml) at 15.56 °C. Density relative to 4 °C water. Density at 20 °C relative to 20 °C water. Density at 25 °C relative to 25 °C water. Freezing temperature, °C. 10 °C. 20 °C. 25 °C.