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oanh.nguyenh oanh.nguyenh
wrote...
11 years ago
well, i know that the water inside starts boiling/bubbling again, but i don't understand why

i heard that cooling the top of the flask causes the steam inside to condense. That lowers the pressure and sucks more vapor out of the hot water, but i'm not sure what it means.  can anybody explain that better to me?  thanks!!!!
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wrote...
11 years ago
Well if I understand what UR saying - the important point., not stated, is that this flask is sealed. Therefore its internal pressure will be lowered by removing heat from the previously boiled (now) hot water.  

At a lower pressure the boiling point of water drops so that indeed it may boil at the lower pressure and, now, reduced temperature.

If your school has a decent vacuum pump ask teacher to demo boiling water at room temperature by merely reducing pressure.
wrote...
11 years ago
If your flask contains boiling water, you dump it out and then immediately pur cold water on the outsiude:

1. some water vapor condenses on the inside of the flask
2. the flask quickly shrinks (this is why flasks are made of very low expansion/contraction glasses)
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