Hey Fellas,
a honeywell guy and myself have been disputing each others claims on air density. i am of the opinion that dry air is denser and he thinks otherwise. care to share your opinions?
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Hey Fellas,
a honeywell guy and myself have been disputing each others claims on air density. i am of the opinion that dry air is denser and he thinks otherwise. care to share your opinions?
The following taken from:-
http://hypertextbook.com/facts/2000/RachelChu.shtml
Density of Air
Edited by Glenn Elert -- Written by his students
An educational, Fair Use website
<TABLE cellSpacing=2 cellPadding=3 width="100%" border=3><TBODY><TR bgColor=#cccccc><TH align=left>Bibliographic Entry</TH><TH>Result
(w/surrounding text)
</TH><TH>Standardized
Result
</TH></TR><TR bgColor=#ffffcc><TD>Cutnell, John D. & Kenneth W. Johnson. Physics. 3rd Edition, New York: Wiley. 1995: 315.</TD><TD align=middle>"Substance, Air, Mass Density (kg/m<SUP>3</SUP>), 1.29, *Unless otherwise noted, densities are given at 0 °C and 1 atm pressure."</TD><TD align=middle>1.29 kg/m<SUP>3</SUP></TD></TR><TR bgColor=#ffffcc><TD>"Atmosphere." Encarta. CD-ROM. Redmond, WA: Mircosoft, 1994.</TD><TD align=middle>"The density of dry air at sea level is about 1/800th the density of water."</TD><TD align=middle>1.25 kg/m<SUP>3</SUP></TD></TR><TR bgColor=#ffffcc><TD>CRC Handbook of Chemistry & Physics. 61st ed. Florida: CRC Press, 1980-1981: F-10.</TD><TD align=middle>"The density of moist air may be determined by a similar relation: D = 1.2929 (273.13/T) [(B - 0.3783e)/760] where T is the absolute temperature; B, the barometric pressure in mm, and e the vapor pressure of the moisture in the air in mm."</TD><TD align=middle>1.2929 kg/m<SUP>3</SUP></TD></TR><TR bgColor=#ffffcc><TD>CRC Handbook of Chemistry & Physics. 48th ed. Ohio: Chemical Rubber Co. 1967-68: A-10.</TD><TD align=middle>"Density of Dry air at 0 °C & 760 mm = 1.2929 g/liter"</TD><TD align=middle>1.2929 kg/m<SUP>3</SUP></TD></TR><TR bgColor=#ffffcc><TD>Horowitz, Irving L. Contemporary Earth Science. New York: Amsco: 1976, 13-15.</TD><TD align=middle>"The density of air at sea level is approximately 1/800th the density of water."</TD><TD align=middle>1.25 kg/m<SUP>3</SUP></TD></TR></TBODY></TABLE>Density (D) is the mass of a given volume of a substance. Density can be obtained by dividing the mass (m) of an object by the volume of that object ...
D = m / VA mass that is concentrated in a small volume has a greater density than a substance of equal mass that occupies a larger volume. Thus, gases have the smallest densities as compared to solids and liquids because gas molecules contain mostly empty space while molecules in liquids are more tightly packed together.
The density of a substance (mainly gases) depends on temperature and pressure. Gases are usually compared at a standard temperature and standard pressure. These are the freezing point (0 °C) and normal air pressure at sea level (760 torr), respectively.
The density of dry air at sea level is 1.2929 kg/m<SUP>3</SUP> or about 1/800th the density of water. But as altitude increases, the density drops dramatically. This is because the density of air is proportional to the pressure and inversely proportional to temperature. And the higher you go into the atmosphere, the lower the pressure gets. Pressure is approximately halved for each additional increase of 56 km in altitude. To determine the density of dry air at a given altitude we could use the relation
D = D<SUB>0</SUB> × (T<SUB>0</SUB> / T) × (P / P<SUB>0</SUB>)Where D<SUB>0</SUB> is the known density at absolute temperature T<SUB>0</SUB> and pressure P<SUB>0</SUB> and D, the density at absolute temperature T and pressure P.
Just as there is a density of dry air, there is also the density of moist air, or air that contains moisture (humidity). To obtain this density you can use the relation
D × (273.15 / T) × [(B - 0.3783 e)/760]
Where...D is the density of dry air at sea level,Rachel Chu -- 2000
T is the absolute temperature in kelvin,
B is the barometric pressure in torr, and
e is the vapor pressure of the moisture in the air in torr.
<TABLE cellSpacing=2 cellPadding=3 width="100%" border=3><TBODY><TR bgColor=#cccccc><TH align=left>Bibliographic Entry</TH><TH>Result
(w/surrounding text)
</TH><TH>Standardized
Result
</TH></TR><TR bgColor=#ffffcc><TD>Eubanks, Steven W. Standard Atmosphere Computations, NASA Lewis Research Center.</TD><TD align=middle>"1.22500 kg/m^3"</TD><TD align=middle>1.225 kg/m<SUP>3</SUP></TD></TR><TR bgColor=#ffffcc><TD>Carmichael, Ralph. A Sample Atmosphere Table (SI units), Public Domain Aeronautical Software.</TD><TD align=middle>"1.225E+0 kg/cu.m"</TD><TD align=middle>1.225 kg/m<SUP>3</SUP></TD></TR></TBODY></TABLE>Editor's Supplement -- 2001
External links to this page.
- Bibliography, David Feldman, Roanoke Valley Governor's School
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Overall I would say that moist air is denser IMHO.
Surely more water molecules in a given volume in air makes it denser because the water weighs more than the air than would otherwise be there in dry air:confused: