Fucking physics, how does it work!?

>> ^gwiz665:

Fucking physics, how does it work!?


The answer's a bit of a letdown.

I knew it would boil. I did not know it would freeze.

If you're ever thrown out of an airlock into space, one of the many sensations you'll feel is the water boiling off of your tongue.

>> ^SuperHotbUNZ:

I knew it would boil. I did not know it would freeze.


Actually, below .006 atm liquid water isn't stable... it either freezes or boils, depending on the temperature. If they had left it in the vacuum then it wouldn't have frozen. As said above this is what happens to a person tossed out of an air lock in space, and it is also closely related to the damage deep-sea divers experience if they surface too quickly.

Another interesting property of H2O is that adding pressure to ice at just under the freezing point (and above .006 atm pressure) turns it back into water, where as most substances freeze under increased pressure.

♥ Chemistry

I'm cornfused? If the water boiled away into water vapor under the vacuum, how did it end up back in the glass as ice when the vacuum was removed?

>> ^Psychologic:
>> ^SuperHotbUNZ:
I knew it would boil. I did not know it would freeze.

Actually, below .006 atm liquid water isn't stable... it either freezes or boils, depending on the temperature. If they had left it in the vacuum then it wouldn't have frozen. As said above this is what happens to a person tossed out of an air lock in space, and it is also closely related to the damage deep-sea divers experience if they surface too quickly.
Another interesting property of H2O is that adding pressure to ice at just under the freezing point (and above .006 atm pressure) turns it back into water, where as most substances freeze under increased pressure.
♥ Chemistry


Phase diagram for general fluids: http://www.teamonslaught.fsnet.co.uk/co2%20phase%20diagram.GIF

Phase diagram for water: http://www.cims.nyu.edu/~gladish/teaching/eao/water-phase-diagram.jpg


These diagrams show what you're describing. Notice the line separating solid and liquid. Under general fluids, the line tilts to the right showing that when pressure is added and temperature is constant, the phase of that fluid will move from liquid to solid. But for water, the line is tilted to the left, showing that with increased pressure at a constant temperature, ice would turn to water

WITCHCRAFT!!!

>> ^jimnms:

I'm cornfused? If the water boiled away into water vapor under the vacuum, how did it end up back in the glass as ice when the vacuum was removed?


Not all of the water boiled off.

When they initially removed the pressure the liquid boiled rapidly because it's temperature was much higher than water's boiling point at that pressure (see the phase diagram linked above). The energy loss from the boiling dropped the temperature of the remaining liquid to it's new lower boiling phase-change point (notice the boiling slows significantly).

Since the pressure was too low for liquid water to exist, any water that hadn't escaped in the boiling instead solidified. From that point any vapor escaping would go directly from solid to gas (like dry ice does at normal pressures).