If you were to sink a container to the bottom of a deep ocean and seal it there,
ID: 1321508 • Letter: I
Question
If you were to sink a container to the bottom of a deep ocean and seal it there, then bring it up to the surface, would it retain its pressure?
The answer for a gas is obviously yes, but what about for a liquid like water which is incompressible? Once the crushing weight of the water column above is removed, does the water retain it's quality of "pressurizedness" or return to normal water? I guess a clear way to test this would be to bottle up a deep water fish and bring it up to the surface and see if it explodes.
While we're at it, what about a solid? Barring any elasticity and incidental temperature change, will a solid object break a non-sealed glass container which is exactly fitted to it and then placed in vacuum?
Explanation / Answer
The problem in your post is that you don't consider the force resisting the water pressure, which is exerted by the walls of your container.
To do this, imagine a two-chamber container, with outer walls infinitely strong, but with a piston in between them which is maintained at its central position by some force that you exert. Chamber A is filled with air at sea level and then closed, chamber B is left open as you sink the container. The force you need to exert on the piston raises as you sink it, in proportion with water pressure, say at some depth it is area times P1. Now close chamber B too. You can now bring your container anywhere, this won't change the balance inside.
And you can still exert the same pressure P1 on the piston, and water is under pressure P1. But you can also vary this pressure on the piston, to any value you like and bring the water to some other pressure level, without having any movement of the piston (as long as you remain in the incompressibility regime). In particular, releasing the force suddenly won't lead to a burst, because water is incompressible.