On a spacewalk, in a vacuum, if an open empty water bottle were capped and squeezed, would it pressurize or collapse as if it were not capped?
Assuming vacuum, a capped bottle would behave in space pretty much the same as an open bottle, in space or on Earth, since the pressure inside and outside the bottle would be the same in all these cases. This means, that, given a sufficient force, the bottle would collapse.
I don't think it would compress. It is already at a vacuum state, so by squeezing the middle, you would force the outer areas out, trying to make a further vacuum(which would be pretty tricky), so the resistance to that would push back on your hand. Slap dash answer but I hope it helps!