Hello, long time lurker, first time poster. I’m hoping this is the proper place for this question.
I was at work, cooking with the pressure cooker when I thought of this.
So, the question: One has a box, infinitely durable, impenetrable, and watertight, allowing nothing in or out, not even heat, and one of the walls of said box was attached to an arm that could force said wall inward, towards the opposite wall(like a car crusher), and this arm was capable of infinite strength. (I use infinite, a lot, though I’m sure there are forces less than infinite that could accomplish this.) This box is filled with pure water, and nothing else. Pressure is applied on the water with the arm.
I figure it must be possible to force the molecules closer together, but to what degree? I’m sure a whole lot of heat would be generated, but would the water be forced into a hot solid, or a plasma? Would manual fission be attained eventually?
Infinite pressure would turn it into a black hole, wouldn’t it?
But first the hydrogen would fuse into helium, and the oxygen would fuse into heavier elements. Then it would turn to neutronium, and then be collapsed into a singularity.
Actually the whole mechanism would turn into plasma first.
I don’t think it would ever be solid. IIRC, even the gases at the core of stars still act like gases, despite the pressure they are under.
Compress it enough, and it will go solid: Possibly to Ice-VI, depending on temperature (I’m assuming it’s close to room temperature), then to Ice-VII, and eventually to Ice-X (phase diagram of water).
Go way past that pressure, and you’d eventually compress it into an electron-degenerate fluid similar to what’s found in a white dwarf, and also eventually start up fusion (I’m not sure which of these would come first). Past both of those, you’ll eventually reach neutron star conditions, and past that, possibly a brief layover at quark star, then black hole. But you certainly can’t call the substance “water” any more at any of those points.
While compressing water while holding the temperature constant will eventually compress it into a solid, compressing water will increase the temperature barring any attempt to hold the temperature constant. Simply compressing water in the manner you describe will never cause it to become solid because it will heat up too much.
Is this the case if the water is thermally insulated from its environment? The OP said that nothing can get into or out of the box, “not even heat”. I should probably know how to handle this problem (adiabatic compression/expansion) for general materials, but my textbooks are at work and I’m really only familiar with the case of a gas.
Good point. I don’t know enough of the details of the mechanical properties of water to say, on that (though I’m certain they’re far more complicated than for an ideal gas). Given the various elastic moduli of water, you could say how much it’d change in volume with pressure, and hence calculate the work done on the water, and with that and the specific heat, you could calculate the temperature change.
