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I've asked a similar question here but the answer given shows the behaviour of water under general conditions.

I'd like to know what the behaviour of water is like as pressures increase towards infinity without being able to escape it's confinement.. i.e. a ball of water at the core of a galactic mass.. maybe this question is more for theoretical physics since we can't really measure or experiment?

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  • $\begingroup$ The answer you got there is likely the one you may receive here. You should really make sure you understand that one before continuing your search. $\endgroup$ Nov 26 '14 at 3:16
  • $\begingroup$ @AndréNeves that last answer is helpful for understanding the behaviour of water under relatively low pressures and temperatures. I'm looking to see what happens after the 'ice' cannot rearrange structure anymore yet pressure continues to increase. $\endgroup$
    – irth
    Dec 1 '14 at 4:05
  • $\begingroup$ I fail to understand what this would be. How much pressure would that be, in pascals? Here, take a look: en.wikipedia.org/wiki/Orders_of_magnitude_(pressure) $\endgroup$ Dec 1 '14 at 12:28
  • $\begingroup$ Cheers, @AndréNeves. That's a good resource. The pressures I'm looking at fall between 10^11 and 10^16 Pa. $\endgroup$
    – irth
    Dec 1 '14 at 22:14
  • $\begingroup$ Then the top region of the chart mentioned in CSE (i.stack.imgur.com/RpaIc.png) is not "relatively low pressure", but in the order of magnitude you want. However, I don't know how very high temperatures (15 million K, core of Sun) would affect the state of the water. $\endgroup$ Dec 2 '14 at 1:39
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Yes, the question is theoretical and so the response. Under enough pressure water will become a solid, regardless of temperature. That is, as far as it is still water. If pressure is high enough, the atoms will collapse and form neutron-degenerate matter (theorized to exist in the cores of neutron stars). I am not sure if there could be an intermediate mixed phase in between water and "neutronium" in which only one of the atoms collapese first (either H or O) and the other at a larger pressure.

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  • $\begingroup$ Some studies suggest that at some pressure point between ice and fusion, water takes on metallic characteristics. $\endgroup$
    – irth
    Dec 1 '14 at 4:06
  • $\begingroup$ Would it be a solid in the core of the Sun (25 PPa, 15.6 MK)? It must be simple, but I couldn't figure that out. $\endgroup$ Dec 2 '14 at 1:42
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Here's the phase diagram for water:

phase diagram

The diagram shows us that at pressures around 1 terapascal (about 10 million atmospheres) ice is solid, at least up to 400 C. It has been predicted (reference_1, reference_2) that at higher pressures, somewhere between 1.5 and 6 terapascals, solid ice will undergo an insulator to metal transition and display properties typically associated with metals (band structure, electrical conduction, etc.). That's around 15-60 million atmospheres.

But, if the pressure was to increase towards infinity, the behaviour of water (without water being able to escape its confinement, say a ball of water at the core of a galactic mass) would be very different...

Suffice to say, it doesn't stay water after a certain point. The intense temperatures created by the compression will cause the water to break apart, eventually no longer even having oxygen atoms due to nuclear reactions. Because we're talking about an externally applied pressure, the Chandrasekhar limit doesn't apply, so there is a point at which electrons and protons combine (when the electron degeneracy pressure is overcome) and a mass of neutrons remains. Neutrons themselves also have a degeneracy pressure (though we don't have good models to predict the exact pressure that has to be overcome). From here, we don't know what happens with as much certainty, but the formation of quark matter has been predicted.

Eventually, we reach a singularity. We can think of this as all the matter we had before being compressed into an infinitesimal volume with infinite density and our applied pressure ceases to mean anything. If we started with enough water, this would behave much like any other black hole, though micro black holes are hypothesized to have some special properties.

Mentions: @ron @ Michael DM Dryden

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  • $\begingroup$ Thank you for an amazing answer with interesting topics to research. If it could be sound to assume that density would increase to match the assumed density of Earth's iron-nickel core, I wonder how electron degeneracy pressure affects magnetic fields. $\endgroup$
    – irth
    Apr 6 at 22:31

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