A bottle of water at 0'C is opened on the surface of moon. What happens and why?
It makes no sound, because the moon has no atmosphere. :uhh:
Any air in the bottle and water will rapidly escape. Any water left would then boil off.
I imagine the same thing as what happens to the ice already on the moon.
but how is it possible?
How is what possible
It's a somewhat more complicated picture than that. Boiling point rises and lowers with increasing and decreasing atmospheric pressure. Since there is no air pressure to speak of on the moon, the boiling point should be much lower than 100C. However, in order to change from the solid (remember it's at 0 degrees initially) it starts as a chunk of ice, and boils off at a rate that depends upon the radiation flux (which would impart sufficient energy to teh H2O molecules to allow them to escape). The higher the flux, the faster it boils off.
Water is a vapor at 0 deg. C in a vacuum. If the water was initially frozen it will sublimate to steam.
That's pretty much what I said. The term "boils off" isn't technically accurate (sublimates off sounds too weird) so perhaps the word choice could have been better, but the idea remains. But the rate does depend upon the radiation flux.
Just because it is at 0deg celcius doesnt mean it is solid. You also didn't specify what pressure the bottle is providing, it is probably not 14.7psi. Another reason why it isn't likely to be solid.
This process will reduce the temperature of the water, however...it won't stay at 0 C. If liquid, it will quickly freeze and boil until it is a mixture of vapor and ice with no remaining liquid. If isolated in the shade, the ice will continue to cool as it sublimates until it gets below around 200K, at which point it'll be stable as a solid. If in the sun or exposed to other sources of heat sufficient to keep it above that temperature, it'll continue to sublimate away. The Apollo astronauts used sublimation units that used this to provide cooling and remove humidity from the air in their suits.
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