In sci.physics, Crown-Horned Snorkack
<chornedsnorkack@[EMAIL PROTECTED]
>
wrote
on Fri, 9 May 2008 06:04:12 -0700 (PDT)
<26d30f45-a3ee-4ab8-ad64-9712f7a160ee@[EMAIL PROTECTED]
>:
> On 9 mai, 15:54, lugoteehalt <lugoteeh...@[EMAIL PROTECTED]
> wrote:
>> On 9 May, 13:40, Crown-Horned Snorkack <chornedsnork...@[EMAIL PROTECTED]
>
>> wrote:
>>
>> > Suppose that you have a really deep body of fresh water - which has
>> > actual temperature of 3,98 Celsius near surface, below a thin layer
of
>> > surface ice and a thin layer of water colder than 3,98 degrees.
>>
>> > As water is lowered from the surface, its density increases
>> > (compression). But adiabatic compression should cause some increase
of
>> > actual temperature, even in liquids and solids.
>>
>> > The melting point decreases up to about 2200 atmospheres (ice Ic),
>> > then begins to rise. Ice VI forms at about 6000 atmospheres, and
>> > actual temperature of about 0,16 Celsius. It is denser than water,
and
>> > naturally its freezing point increases with pressure.
>>
>> > At which temperature and pressure would ice VI come to equilibrium
>> > with fresh water adiabatically compressed from 0 atm 3,98 Celsius?
>>
>> "and naturally its freezing point increases with pressure." Hope I'm
>> not being dense, little pun, but could you explain this assertion?
>> Are you absolultely certain it is true?
>
> Yes, absolutely.
http://www.lsbu.ac.uk/water/phase.html
is a reasonably good schematic representation of
temperature versus pressure versus phase, for (presumably
reasonably pure) water. According to it, Ice VI forms around
1 GigaPascal (just under 10,000 atmospheres) and will melt
at 300 K.
http://www.chemicalogic.com/images/phase_diagram.gif
suggests 6,000 atmospheres along the path it diagrams
(which generally goes up from 273 K or 0 C).
>
> The freezing/melting point of ice Ic decreases with pressure because
> water is denser than ice (and water has latent heat of freezing - heat
> is released when water freezes). All substances which expand on
> melting have melting point that increases with pressure, and this
> includes high-pressure ices. (The exception is helium 3, whose melting
> point decreases with pressure because, although it expands on melting,
> it also releases heat on melting).
--
#191, ewill3@[EMAIL PROTECTED]
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