Temperature and Pressure
The density of dry air can be calculated using the ideal gas law, expressed as a function of temperature and pressure:
where ρ is the air density, p is absolute pressure, Rspecific is the specific gas constant for dry air, and T is absolute temperature.
The specific gas constant for dry air is 287.058 J/(kg·K) in SI units, and 53.35 (ft·lbf)/(lbm·R) in United States customary and Imperial units.
Therefore:
- At IUPAC standard temperature and pressure (0 °C and 100 kPa), dry air has a density of 1.2754 kg/m3.
- At 20 °C and 101.325 kPa, dry air has a density of 1.2041 kg/m3.
- At 70 °F and 14.696 psi, dry air has a density of 0.074887lbm/ft3.
The following table illustrates the air density–temperature relationship at 1 atm or 101.325 kPa:
| Temperature | Speed of sound | Density of air | Acoustic impedance |
|---|---|---|---|
| in °C | c in m·s−1 | ρ in kg·m−3 | Z in N·s·m−3 |
| +35 | 351.88 | 1.1455 | 403.2 |
| +30 | 349.02 | 1.1644 | 406.5 |
| +25 | 346.13 | 1.1839 | 409.4 |
| +20 | 343.21 | 1.2041 | 413.3 |
| +15 | 340.27 | 1.2250 | 416.9 |
| +10 | 337.31 | 1.2466 | 420.5 |
| +5 | 334.32 | 1.2690 | 424.3 |
| 0 | 331.30 | 1.2922 | 428.0 |
| −5 | 328.25 | 1.3163 | 432.1 |
| −10 | 325.18 | 1.3413 | 436.1 |
| −15 | 322.07 | 1.3673 | 440.3 |
| −20 | 318.94 | 1.3943 | 444.6 |
| −25 | 315.77 | 1.4224 | 449.1 |
Read more about this topic: Density Of Air
Famous quotes containing the words temperature and/or pressure:
“This pond never breaks up so soon as the others in this neighborhood, on account both of its greater depth and its having no stream passing through it to melt or wear away the ice.... It indicates better than any water hereabouts the absolute progress of the season, being least affected by transient changes of temperature. A severe cold of a few days’ duration in March may very much retard the opening of the former ponds, while the temperature of Walden increases almost uninterruptedly.”
—Henry David Thoreau (1817–1862)
“By school age, many boys experience pressure to reveal inner feelings as humiliating. They think their mothers are saying to them, “You must be hiding something shameful.” And shucking clams is a snap compared to prying secrets out of a boy who’s decided to “clam up.””
—Ron Taffel (20th century)