Dam -
I don't know what the exact value you're looking for is, but I
think I can answer your question. An easy way to think of this is to
look at the "phase diagram" for water. This is basically just a graph
showing the water's state of matter at different temperatures and
pressures. The lines between the states show the boiling points,
melting points and sublimation points:
As you can see, as the pressure falls, so does the boiling point.
Just by looking at the graph, you can see that the boiling point is
around room temperature at about 0.1 atm (or about 75 torr). At
pressures much lower than this, such as the one you mentioned, the
boiling temperature will be significantly below zero degrees Celsius.
So it seems unlikely that, at room temperature, your problem is
condensation.
Further, you may have noticed on the graph that below a certain
pressure (the "critical point"), it can not exist in the liquid phase
at all. It changes directly from a gas into a solid, or vice-versa. For
water, this pressure is about 0.006 atm (or about 4.5 torr). So at the
pressures you're talking about, it would not be possible for the gas to
"condense", persay.
-Tamara
(published on 10/22/2007)
