Naked Science Forum
Non Life Sciences => Chemistry => Topic started by: neilep on 05/10/2007 16:47:00
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Hullo,
If I could put water in a container strong enough to withold the pressure, could the water still freeze being unable to expand ?...or is that impossible and nothing can contain it ?
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WOW thats a great question.. where did you pull that one from???
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WOW thats a great question.. where did you pull that one from???
My boy asked me it !....kids are a great source !!..
...just mash em up...add some cream and chives and you have a great kid sauce !!
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What will happen is this : as part of the water starts to freeze, the volume will increase, but because there is no room for expanding the pressure will rise. This will lower the freezing point, preventing the water from freezing farther.
How much that pressure will rise will depend on the elasticity modulus of the material your container is made off.
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What will happen is this : as part of the water starts to freeze, the volume will increase, but because there is no room for expanding the pressure will rise. This will lower the freezing point, preventing the water from freezing farther.
How much that pressure will rise will depend on the elasticity modulus of the material your container is made off.
THANK YOU very much Eric.....so....assuming I had a unit with no elasticity at all...nil !...zero !....does this mean that what ever the temperature....the water will never freeze ?
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WOW thats a great question.. where did you pull that one from???
My boy asked me it !....kids are a great source !!..
...just mash em up...add some cream and chives and you have a great kid sauce !!
*Smiles*
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What will happen is this : as part of the water starts to freeze, the volume will increase, but because there is no room for expanding the pressure will rise. This will lower the freezing point, preventing the water from freezing farther.
How much that pressure will rise will depend on the elasticity modulus of the material your container is made off.
that is interesting..
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Hullo,
If I could put water in a container strong enough to withold the pressure, could the water still freeze being unable to expand ?...or is that impossible and nothing can contain it ?
There has been a thread exactly on this question on an italian forum of physics, 2 months ago.
Given the known values for water of :
thermic dilatation coefficient at constant P: a = (1/V)(∂V/∂T)P
isothermal compressibility coefficient: k = -(1/V)(∂V/∂P)T
Clapeyron coefficient: b = dP/dT at equilibrium between the two phases
It's possible to compute the pressure variation with temperature at constant volume:
w = (∂P/∂T)V
since it can be proven that w = a/k
and then we cam compare it with b.
a = -1*10-4 K-1 at P = 1 atm, T = 273 K
k = 4.6*10-10 Pa-1 at P = 1atm
b = -1.3*107 Pa/K.
So w = -2.1*105 Pa/K
Then, since it results that |w| < |b|, water cannot remain in the liquid form = must freeze.
Non-intuitive result, indeed.
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The water could still freeze, you would just need to cool it more (but not much). The freezing point of water depends on the ambient pressure. So, as the water starts to freeze, the pressure would increase (since the volume can't increase). At higher pressure, the freezing point of water decreases, but not by much. The line in the pressure vs. temperature phase diagram of water is almost vertical, but with a slight leftward slope.
Of course, you might not have normal ice when you're done, as you may go into another solid phase from normal ice.
Dick
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What will happen is this : as part of the water starts to freeze, the volume will increase, but because there is no room for expanding the pressure will rise. This will lower the freezing point, preventing the water from freezing farther.
How much that pressure will rise will depend on the elasticity modulus of the material your container is made off.
All of this assumes that the water will attempt to expand by increasing its pressure on its container, but will fail to make much inroads.
On the other hand, as has been mentioned above by Alberto, and in another thread, ice can exist in different forms. Can you freeze water directly into another form of ice (e.g. by changing the ambient pressure of the water before it freezes) such that the water will not increase either pressure or volume as it freezes?
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The water could still freeze, you would just need to cool it more (but not much). The freezing point of water depends on the ambient pressure. So, as the water starts to freeze, the pressure would increase (since the volume can't increase). At higher pressure, the freezing point of water decreases, but not by much. The line in the pressure vs. temperature phase diagram of water is almost vertical, but with a slight leftward slope.
Yes, this is the word explanation of the formulas I wrote. Water pressure increases because of water expansion, of an amount X for every 1°C of temperature decreasing, but this is not enough to keep water liquid, because, for that pressure variation, freezing point has decreased of less than 1°C.
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Water has a number of solid phases, the one we normally see is a low pressure form. If you had water under great pressure in the first place and cooled it it would freeze and contract.
According to this page
http://www.lsbu.ac.uk/water/phase.html
you don't get ordinary ice above about 200MPa pressure.
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What if your container was the center of a black hole... is there a terminal amount of water possible to break past the gravitational pull, or will the pressure be so great it stays in liquid form? What would happen?
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What if your container was the center of a black hole.
A black hole is completely a different question. Matter is compressed to the point where it looses the distinctiveness of the individual atoms. Thus, one essentially no longer has water.
Look at the chart by Bored Chemist above.
In a similar question, I found the densities of several of the forms of high pressure ice.
http://www.thenakedscientists.com/forum/index.php?topic=41158.msg370404#msg370404
Most of the high pressure forms of ice actually had a density greater than 1 (no expansion).