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From: doetnietcomputeren on 10 Feb 2010 09:45 On 2010-02-10 15:34:46 +0100, Mark Olson <olsonm(a)tiny.invalid> said: >>>> Oh - btw, 3 degree water doesn't exist unless someone added alcohol to >>>> it. It stops at 4C then the next phase change is ice. >>> What? Surely the freezing point of normal water is 0 degrees C, and >>> lower still for salt water? >> >> Nope there is a point where it has to drop energy to go through the >> phase change to ice. I don't have links and can't be arsed looking, >> but seawater will only go to 4C. Th energy to do the phase change is >> worth those other 3C. Google it. I'm sure it is out there somewhere. > > You are confused. Fresh water freezes at 0C, sea water at less than > zero C. This link has a likely explanation of your 4C confusion. > > http://www.tpub.com/content/aerographer/14269/css/14269_62.htm Thanks for that, I thought my basic science was all fiction. -- Dnc
From: M J Carley on 10 Feb 2010 09:46 In the referenced article, Kevin Gleeson <kevingleeson(a)imagine-it.com.au> writes: >Nope there is a point where it has to drop energy to go through the >phase change to ice. I don't have links and can't be arsed looking, >but seawater will only go to 4C. Th energy to do the phase change is >worth those other 3C. Google it. I'm sure it is out there somewhere. Naaah. Sea ice begins forming in the northern Bering Sea as late as November, as the ocean reaches a temperature of -1.7�C, the freezing point for saltwater in this area, ... http://www.beringclimate.noaa.gov/essays_mcnutt.html As it happens, you can get pure water down to about -40C before it freezes, if you're careful. -- Si deve tornare alle basi: Marx ed i Clash. Michael Carley: http://people.bath.ac.uk/ensmjc/
From: Kevin Gleeson on 10 Feb 2010 09:58 On Wed, 10 Feb 2010 08:34:46 -0600, Mark Olson <olsonm(a)tiny.invalid> wrote: >Kevin Gleeson wrote: >> On Wed, 10 Feb 2010 15:00:58 +0100, doetnietcomputeren >> <doesnotcompute(a)gmail.com> wrote: >> >>> On 2010-02-10 14:55:01 +0100, Kevin Gleeson > >>>> Oh - btw, 3 degree water doesn't exist unless someone added alcohol to >>>> it. It stops at 4C then the next phase change is ice. >>> What? Surely the freezing point of normal water is 0 degrees C, and >>> lower still for salt water? >> >> Nope there is a point where it has to drop energy to go through the >> phase change to ice. I don't have links and can't be arsed looking, >> but seawater will only go to 4C. Th energy to do the phase change is >> worth those other 3C. Google it. I'm sure it is out there somewhere. > >You are confused. Fresh water freezes at 0C, sea water at less than >zero C. This link has a likely explanation of your 4C confusion. > >http://www.tpub.com/content/aerographer/14269/css/14269_62.htm Fair call, I was going on 30 year old dive training memory and was told that you couldn't dive in water less then 4C as it didn't exist. Your explanation there is more succinct but still gives the same result. There is still that phase change at 4C ( and that article explains that the change is rapid), but my memory (or people's understanding of it when I was doing physics and dive training) still means you are unlikely to dive in water under 4C.
From: Mark Olson on 10 Feb 2010 10:00 Kevin Gleeson wrote: > On Wed, 10 Feb 2010 08:34:46 -0600, Mark Olson <olsonm(a)tiny.invalid> > wrote: > >> Kevin Gleeson wrote: >>> On Wed, 10 Feb 2010 15:00:58 +0100, doetnietcomputeren >>> <doesnotcompute(a)gmail.com> wrote: >>> >>>> On 2010-02-10 14:55:01 +0100, Kevin Gleeson >>>>> Oh - btw, 3 degree water doesn't exist unless someone added alcohol to >>>>> it. It stops at 4C then the next phase change is ice. >>>> What? Surely the freezing point of normal water is 0 degrees C, and >>>> lower still for salt water? >>> Nope there is a point where it has to drop energy to go through the >>> phase change to ice. I don't have links and can't be arsed looking, >>> but seawater will only go to 4C. Th energy to do the phase change is >>> worth those other 3C. Google it. I'm sure it is out there somewhere. >> You are confused. Fresh water freezes at 0C, sea water at less than >> zero C. This link has a likely explanation of your 4C confusion. >> >> http://www.tpub.com/content/aerographer/14269/css/14269_62.htm > > Fair call, I was going on 30 year old dive training memory and was > told that you couldn't dive in water less then 4C as it didn't exist. > Your explanation there is more succinct but still gives the same > result. There is still that phase change at 4C ( and that article > explains that the change is rapid), but my memory (or people's > understanding of it when I was doing physics and dive training) still > means you are unlikely to dive in water under 4C. The simple fact is fresh water does indeed freeze at 0C and not 4C. Sea water freezes at some lower temperature depending on the salinity. There is no phase change at 4C. "Phase change" has a specific meaning.
From: Switters on 10 Feb 2010 10:12
On Wed, 10 Feb 2010 13:20:10 GMT, boots wrote: > Current UK sea temperatures will be > around 7 or 8 degrees in the south Feels colder at the moment[1]. I was in it[2] at the weekend and it feels the coldest it has been for a number of years. [1] I don't think it actually is colder than 7C, it just feels it. [2] South West Cornwall |