trying to figure this out wrote:
Where does the oxygen go?
malmo wrote:
Up.
Less dense air rises. Warm air rises.
Dense air falls. Cold air falls.
trying to figure this out wrote:
1) Are you saying there is more oxygen in air at higher altitudes;
No and that's not implied in anything I've said.
trying to figure this out wrote:
2) Brian is relating humid with hot vs dry air with cold, which seems to obfuscate which has the higher O2 or whether it remains the same;
Obfuscate? No it doesn't.
trying to figure this out wrote:
3) Malmo are you saying cold air is more dense and yet contains less O2? It seems that more dense would mean more O2. What are you meaning by density, as you stated all air at the same temp and pressure has the SAME # of molecules, therefore the density should be the same.
Where did I say that cold air has fewer oxygen molecules?
All air at the same pressure and density has the same # molecules -- that's ALMOST correct and I've not said anything contradictory. However. If you take dry air, that is warm enough, and close to an adequate water source it will take on water vapor. When it does, the density of the now saturated air will be less.
If the air is not sufficiently warm enough, a water source won't mater, even if you heat it, the water will immediately condense.
trying to figure this out wrote:
It seems to me that the O2 in the air does not change significantly, if at all, due to water vapor in the air. A problem with higher dew points is that water is not able to evaporate from the skin for dissipation of heat.
http://en.wikipedia.org/wiki/Humidity
I never said that the Oxygen in the air changes "significantly" but it does change. Changes in air density due to heat and humidity are enough that pilots factor it into their takeoff/landing speeds and acceptable flying altitudes. There is a long history of dead pilots that have made fatal oversights.