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Understandably, there is a clear-cut difference between liquids and gasses. Gasses being more compressible, liquids less so. If you bring a volume of air sealed in a container from sea level to 10k feet (3048m), when you open the container, the relative volume around the container has decreased considerably and upon opening the container, it lets out a discernible sound. Clearly, there is a volume difference as less pressure allows the air/gasses to expand. What if you were to bring up, say, 100ml of water from a depth of 11,000m, would it be the same volume if you brought that same sealed sample to sea level and opened the seal? Knowing that you can't pressurize liquids as you can gasses, I'm simply curious: how much would a liquid expand if brought up from the deepest part of the ocean?

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marked as duplicate by John Rennie, Gert, Jon Custer, Kyle Kanos, Buzz Dec 9 '18 at 2:02

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  • $\begingroup$ Can you explain what you mean by "relative volume"? $\endgroup$ – probably_someone Dec 6 '18 at 11:41
  • $\begingroup$ the relative volume meaning that if a 100ml sealed bag of air were taken to altitude, it would expand due to the lack of external pressure, therefore giving it an apparently larger 'volume': relative volume. $\endgroup$ – Corey Dec 6 '18 at 12:08
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    $\begingroup$ Also, from Wikipedia (en.wikipedia.org/wiki/Properties_of_water#Compressibility): "The low compressibility of water means that even in the deep oceans at 4 km depth, where pressures are 40 MPa, there is only a 1.8% decrease in volume." $\endgroup$ – probably_someone Dec 6 '18 at 12:08
  • $\begingroup$ So does "relative volume" apply to a fluid inside an expandable, sealed container, or does it refer to the behavior of the fluid after a non-expandable, sealed container has been opened? Your comment and your question say different things on this point. $\endgroup$ – probably_someone Dec 6 '18 at 12:11
  • $\begingroup$ well actually i'm kind of wondering both- a depth-sealed container's behavior at the surface (prior to opening, like a ziplock bag full of pressurized water), and also a depth-sealed volume's expansion at the surface (after opening). my apologies, I'm trying to explain a thought I have little knowledge of in my head, but a big question about hah $\endgroup$ – Corey Dec 6 '18 at 12:17
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I'm simply curious: how much would a liquid expand if brought up from the deepest part of the ocean?

Yes, but very little. As you can see on this chart, you can compress it 1% with 200 bar, and it rises very little after that. Someone points out that it's still only 1.8% even when you're really deep.

But I can't explain it nearly as well as as Isaac Asimov did in one of his short essays. He explores what happens when a ship sinks, with the ultimate goal of answering whether there's some depth you get to where it stops sinking because the surrounding density is too high. Short answer: no. But as always, his explanation of how to get there is what is worth reading. Unfortunately my google-fu is not finding a copy.

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    $\begingroup$ Terry Pratchett runs with the possibility in your last paragraph in his novel Going Postal (see what-if.xkcd.com/138). $\endgroup$ – probably_someone Dec 6 '18 at 17:22
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You are correct that the gas and liquid are both compressible, but the liquid less so. So the difference in their behavior depends on how strongly you can constrain the compressed liquid when bringing it to the surface.

The expansion of the liquid (or gas) will reach mechanical equilibrium with its container depending on the compressibilty of the liquid and the compressibility/flexibility of the container. Your ziploc bag at ambient conditions cannot exert much force on the water, but if you have a rigid container that is relatively incompressible then yes, the liquid water will spray out when you open it.

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