Boiling Point and Altitude
Name: Jim H.
Water boils at lower temperatures at higher altitudes - a
method used in early attempts to survey the Himalaya. I have written a
children's book on Everest, to be published later this year and am trying
to provide the information about boiling temperatures. Does anyone know
the temperatures for boiling water at the following (approx.) levels -
2000m; 4000m; 6000m; 8000m ?
I found that pressure in atmospheres, follow the relation:
p = e^(-ay) where p is pressure in atmospheres, a is 1.16*10^-4 m^-1 and y
is altitude in meters.
From my chemistry text, log (Po/P) = (deltaH/W)((1/T)-(1/373))
where Po is sea level pressure (atmospheres), P is pressure, deltaH is
40,700 J/mol, W 19.15 [this is a constant of proportionality from the
linearization of a Vapor pressure (atm) vs Temperature
graph. Specifically, log p = (-deltaH/19.15*T) + C], T is boiling point
desired and 373 is boiling point of water at one atmosphere.
My answers for several altitudes are:
2000 m 93.4 C
4000 m 87.3 C
6000 m 81.3 C
8000 m 75.5 C
I hope this helps!
Nathan A. Unterman
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Update: June 2012