[NatureNS] when water freezes?

Date: Mon, 14 Jan 2008 20:09:57 -0500
From: Gerald Ruderman <naturens@zdoit.airpost.net>
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Andy,

It has been a long time since I took physical chemistry, but I have been 
in wet earth much more recently. Could the explanation for the more 
solid ground be that there was less water around? That is, it had 
drained or evaporated away.

On to water: As heat leaves water it cools to 0C. As more heat leaves it 
stays at that temperature as liquid until enough heat leaves to form 
ice. Water has its maximum density at 4C. I don't know whether this 
could have caused any of what you observed.

Andy Moir/Chris Callaghan wrote:
> 
> I have a question about the properties of water as it goes through the 
> transition from liquid to solid.
> Yesterday, following the heavy rains and mild temperatures, our stable 
> yard was quite a mucky mess.  It was easy to sink well past one's ankles 
> in mud.  This morning when I went out, the ground was not frozen, but it 
> was certainly much more solid to walk over.
> When I went out this morning, the temperature was +2.3C.  The overnight 
> low was +1.8C.
> There were still pools of water in the footprints (and hoofprints) made 
> in yesterday's muck, so the ground certainly wasn't frozen, and there 
> was certainly enough water around to make it every bit as mucky as the 
> day before.
> So the question is, does water begin to "harden" before it actually 
> becomes ice?  I understand that the activity (of the molecules?) slows 
> as the temperature drops, but when I stick my hand into cold water (say 
> water just above freezing), it feels every bit as liquid as when I put 
> my hand into lukewarm water. If there is a "hardening" process before 
> forming ice, does it happen in a very narrow band of temperature just 
> above the freezing point?
> I've tried to find an answer to this burning question on the internet. I 
> found several sites that talked about super cooled water and the way 
> the molecules line up in different ways in liquid water and ice, but 
> nothing that explained why water that should still be liquid appears to 
> be more solid, but not frozen, as the temperature drops to near freezing.
> Thanks,
> Andy Moir
> Freeport  
>  
>  

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