Why water freezes at low pressure?

[goku]

water freezes instantly on very low pressure, irrespective the temp being well above zero. pls explain why? .what can be added to water so that it does not freeze at very low preesure (15mtorr)?

 

[Mapes]

When evaporating water molecules detach from the condensed phase, they take energy with them. The remaining material cools down at the interface. So you could stir the water to maintain the temperature above freezing, or you could add something soluble (like salt) to depress the freezing temperature.

 

[cragar]

evaporation is a coolong process . just like when you put water on your finger and wave it around in the air it feels cooler , you could put anti-freeze in it.