Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: annie123 on 20/10/2013 19:44:06
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i watched a programme called the Secret Life of ice in which a man took a bottle of water cooled by a bowl of ice - didn't say for how long - and then banged it on a table and ice started to appear and eventually mostly filled the bottle. I tried this - several times - with varying degrees of coldness of the bottle and the ice didn't form. Does this only work on tv?? Or should I have had a smaller bottle - i would have tried this but didn't have one - only a litre bottle.
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It's real.
You have to get the water below freezing point without it freezing.
This so called "supercooled" water isn't stable- it turns to ice when disturbed.
Since the water has to be cooled below freexing he can't have just cooled it in ice. It may have been a bowl of ice and salt.
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I haven't done the experiment myself, but it apparently works.
The Latent heat of fusion of water is 79.5 calories per gram.
It takes about 1 calorie to heat or cool 1 gram of water by 1°C.
Since it is unlikely you would ever reach super cooled water at -80°C, the resulting ice you create from the bump is likely more of a slush than a solid ice.
Say, if you begin with the container supercooled to -5°C, then immediately after the freezing transition, the temperature of the container should increase to 0°C.
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I tried it again with a smaller bottle and it worked, but as you say when the temp rose even a little it became water again. I poured it out into a glass and it was mostly water that came out with eventually a little slush of ice crystals.