Naked Science Forum
General Science => General Science => Topic started by: Lex on 01/08/2005 03:10:47
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Why does ice form only on the top of a lake?
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I would have thought that it may be because it's in direct contact with the atmosphere, and that when the ice forms it creates a seal that insulates below the top...or something like that. Movement of the water may also be a contributing factor !
Lets hope a passing ice-on-lake expert drop's in with the answer.
welcome to the site Lex.
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Finstagiber.net%2Fsmiliesdotcom%2Fcontrib%2Ficw%2F003.gif&hash=f326f525e3f6c60d4ea3ecbb24d1df2a)Men are the same as women.... just inside out !!(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Finstagiber.net%2Fsmiliesdotcom%2Fcontrib%2Ficw%2F003.gif&hash=f326f525e3f6c60d4ea3ecbb24d1df2a)
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I maybe stating the obvious but maybe its because its cold.
WOW 100 posts, Neil it wont belong before i've caught up to you
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Firstly, it's because water has a very unusual property - it is denser as a liquid than as a solid (thus, ice floats). In fact, water is densest at 4degC. As a large sample of water cools toward freezing, there forms a zone of 4 degree water at the bottom. If it's cold enough for long enough, it is possible for an entire sample of water to freeze entirely. Puddles and small ponds typically do freeze all the way through. Neilep is right that the solid ice does act as a thermal insulator; this has the effect of protecting deeper water from freezing. Most lakes are deep enough that it would take an impossibly cold and/or long winter to freeze them completely.
By the way - I have seen this property (denser liquid than solid) described as "virtually unique" to water. Does anybody know of other such substances?