Quote:
On 2003-02-18 14:53, DaveC wrote:
It's implied, but not clearly stated that a glass of water taken into a vacuum will boil until it freezes. The vaporization of the water from the surface removes heat from the only source it has - the liquid water itself, assuming the container is shielded from the sun. Once the water in the glass is frozen, it will continue to cool towards absolute zero as ice from the surface sublimes into the vacuum - again taking heat from the ice that remains behind. So the answer is water both boils and freezes in a vacuum.
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That sounds about right, as the water boils it loses energy as the latent heat of vaporisation, which is fair quantity of energy per unit mass. Temperature drops until it is below the melting point of water in a near vacuum, and the water thus freezes.
The cool thing is you can repeat this on earth in an atmosphere. Take a saucer of water (or a puddle if you want) and pass dry air over it. Water will vaporise into the dry air cooling the temperature of the main body. Pass enough dry air over the water and you can freeze it, although this is quite difficult in practise due to conductive heat from the container that you use....
<font size=-1>[ This Message was edited by: Mainframes on 2003-02-19 05:19 ]</font>
<font size=-1>[ This Message was edited by: mainframes on 2003-02-20 05:52 ]</font>