# Can water be liquefied or solidified just by adjusting the temperature, regardless of the pressure?

technically the line between liquid and solid phase would go a long way before hitting the y-axis, but the point is it will eventually.

So the question remains, can any liquids, including water (with its unique phase diagram) be liquefied regardless of the pressure?

• This is not an accurate Phase diagram of water. Here you can see a better phase diagram. What do you mean by "can any liquids, including water (with its unique phase diagram) be liquefied regardless of the pressure" – Gowtham May 3 '15 at 13:22
• @Gowtham my point is since the solid-liquid equilibrium line is sloped inward towards the y axis, theoretically it will hit eventually. – user134789 May 3 '15 at 13:28
• Did you check out the link, Do you ask "can water exist as equilibrium between solid and liquid at some temperature regardless of the pressure "? sorry i really dont get what you are trying to ask.. On the line in the phase diagram, both the phases exists at same time given some T and P in a dynamic equlibrium. If you move away from the line, it will transform to a single phase(if we go to one phase region) or two-phase(move to another part of a line) – Gowtham May 3 '15 at 13:32
• Here is my questions: no matter what the temperature is, just by adjusting temperature, so if you pick a fix y coordinate and change x coordinate, can you ALWAYS liquefy or solidified water? See the picture, above a certain pressure so will be no solid state? – user134789 May 3 '15 at 13:38
• you can add your last comment to your question, so that it is more clear. – Gowtham May 3 '15 at 13:52

If I actually understood your question correctly, yes there are regions above which there will be only solid state (rather than no solid state). This is limited to the molecular region.

The Roman numerals indicate various ice phases.

From the above phase diagram (which can be found here) the solid-liquid equilibrium line doesn’t touch the y-axis as you suggest. But there will be only solid phase above the $10\ \mathrm{GPa}$ region(approximately).

In the phase diagram you drew, if (a big if) such a PD exists for some element/molecule, then there will be no solid above the point where solid-liquid line meets y-axis.

As pointed out in the comments, when we reach high temperatures and pressures we won’t be seeing the molecular water. It will dissociate into atoms/ions as shown in the figure.

• This is correct, though actually even above $1\:\mathrm{TPa}$ water doesn't necessarily stay solid no matter what you do. Raise the temperature to solar-interiour values, and the water will stop being water at all... – leftaroundabout May 3 '15 at 17:19
• I assume at some temperature (i.e. in the sun's core there are no molecules) water will decide it wants to freely disassociate into atoms, but I have no idea what that would be (order of magnitude). So presumably there might be a pressure at which "H2O" (what's the disassociation constant in high-temperature ice...) is never not a solid. – Nick T May 3 '15 at 19:58
• sandia.gov/pulsedpower/prog_cap/pub_papers/… has a theoretical phase diagram for water at extremely high pressure and temperature (speculating that these conditions might exist in the interior of Uranus and Neptune). The basic observation appears to be that, at very high pressures, water will go from ice to an exotic "superionic" semi-dissociated semi-fluid phase as you raise the temperature, and from there directly to plasma. – zwol May 3 '15 at 21:11
• Good discussion. One minor point in the diagram you cite: Ice VII is still molecular. Ice X is when you get to a nonmolecular structure in the fully solid state. – Oscar Lanzi Feb 22 at 23:43

Theoretically, YES!

But why? In the real world there are a thousand different ways to accomplish a certain task, but only a few will be the most efficient. So in considering your question.

So the question remains, can any liquids, including water (with its unique phase diagram) be liquefied regardless of the pressure?

First of all, I do not like how you put regardless of the pressure, there has to be a certain amount of pressure. Yes you can do this, but there really is an easier way to this. Use a freezer to solidify it, or leave it out in the open to liquify it. :)

• I think the OP is confused about phase diagrams , not about practicality of anything. – Gowtham May 3 '15 at 14:11
• He doesn't look confused about it. He just wants to know if this is possible. – Asker123 May 3 '15 at 14:13
• I didn't know what is outside the picture students are usually given, the one that shows solid phase above a certain pressure. The one in Gowtham's answer. – user134789 May 3 '15 at 16:41