Title pretty much says it all … if you took a soaking wet sponge , put it in a vacuum chamber and extracted all the air, would the water be removed from the sponge?
Well, some water would evaporate. How much would depend on the size of the container and the temperature. For small chambers, standard temperatures, and a very wet sponge, not much of the water will be able to evaporate before it re-condenses on the sponge at the same rate it’s evaporating.
And if the vacuum is continuously being renewed by ongoing suction, all the water would eventually go to vapor and leave the sponge quite dry.
Also it would depend on how fast the vacuum was pulled. If fast enough the water turning to vapor would also turn some of the water into ice. And if the vacuum was maintained as the ice melted that water would also turn into vapor and be removed.
Hmmm … I was thinking more along the lines of a three chamber sealed system … Chamber 1 is at atmospheric pressure …chamber 2 is a small airlock chamber …Chamber 3 is a total vacuum chamber.
You stick the sponge in chamber 2 (which is obviously at atmospheric pressure, just like chamber 1 ) you then seal off chamber 1 from chamber 2, and you open the seal between chamber 2 and chamber 3.
For the purposes of discussion, chamber 3 ( the vacuum chamber ) is massively larger than chamber 2, so the small amount of air admitted to chamber 3 by the opening of the seal between chambers 2 and 3 is for all intents and purposes irrelevant.
Would the sponge instantly dehydrate?
The water will boil in the vacuum. It’s not hot, it just turns to vapor under the low pressure. In vaporizing the water may suck up enough heat for some of it left in the sponge to freeze. Depends on how warm the sponge and the container itself were in the first place. It’s barely different from just putting a beaker of water in a vacuum chamber, the water will boil when the pressure drops far enough. I’ve never watched an entire beaker of water boil off in a vacuum so I don’t know if any freezing will occur.
I remember an anecdote* about an astronaut in training (not an astronaut-in-training, mind you) who suffered a spacesuit failure in a vacuum environment. He said the last sensation he felt before he passed out was the saliva boiling off of his tongue.
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- ain’t that a purty cite?
The sponge would certainly die, if the third chamber was large enough each of the poor animal’s cells would rupture with its cytoplasm boiling off … the remaining partial desiccated pile of goo would start to break down and various volatile compounds would vaporize and redeposit on the inside of the chamber … it would be a mess that’s for sure …
Cute answer there ww49. Completely valid, correct, and unexpected. Well played. 
Tripolar really nailed it. The sponge itself is immaterial. Most of the water will evaporate into the vacuum.
If the connection between chambers 2 & 3 is large & you slam the valve wide open the evaporation will happen real quickly and probably form some ice that will then slowly sublimate. Conversely, if the connection is small or the valve is just barely opened, the process will be much slower as chamber 2’s pressure very gradually bleeds down to nil
Well, I have done this exact thing. The water boils until it freezes. I know that sounds contradictory, but that is what happens. I placed a wet foam pillow insert (squeezed as dry as I could) into a large vacuum chamber that pumped down to less than 50 microns in about 40 minutes, then stayed there for an hour or so. When we pulled it out, the core was frozen solid and took a loooong time to thaw since the foam acted as an insulator. I have also observed small water leaks in very high vacuum chambers and it freezes into delicate sprays, then eventually sublimates and goes away.
Dennis
Note that you need a high-volume vacuum pump. The small amount of water turns into an immense amount of gas, which all has to be pumped out. The degree of vacuum achieved will be less important than the volume of gas removed.
Also, the energy required to boil the water is still the same. If you are only using sublimation, your vacuum pump has to provide that energy.
It should only sound contradictory to those who didn’t learn in chemistry class that boiling is actually a cooling process.
In boiling, the hotter atoms/molecules of the liquid leave the liquid, moving outward into the surrounding air or empty space. What particles remain in the liquid are the cooler ones. Hence, it’s a cooling process.
Tell that to the lobster…
Only on the Dope!
I know you’re kidding, but from the water’s POV, the lobster *is *a cooling process. A bigger one than the boiling.
At least for awhile until all the lobster’s “coolness” is used up.
Yet further proof that perspective is everything.
That’s exactly what I thought when I read that post. This place is awesome.
In case Chronos is reading, yes this was at the Zero G Facility. I also used to clean oil stained collectible pottery in a vacuum oven. Amazing to watch the old brown oil running out of the hairline cracks. I actually have a fairly good sized vacuum pump at home. I used to keep my eye open for a decent bell jar but never found one. Otherwise I would film a frozen sponge for the cause.
Dennis
Oh, I’m reading. And I once microwaved liquid nitrogen for the Dope, so I can relate.
I love it, I never thought about LN2 in the nuker. Have you tried O2 or H2 yet?
Dennis
You’re freeze-drying the sponge without the “freeze” part.
Seriously, all the water would be removed from the sponge. If freeze-drying can remove all the water from my freeze-dried apples, even though they have pretty low residual energy to boil off (because you lowered the temperature) or from my freeze-dried taxidermy, it ought to make short work of a wet sponge at room temperature.
Think of it as an equilibrium problem – some portion of the water is always picking up enough energy to bump it off of the wet sponge. In equilibrium, you have an equal amount of water coming out of the humid air to wet the sponge. On a dry day, with no humidity, there is very little water to re-wet the sponge, and the sponge dries out. A vacuum is the ultimate low humidity day, with no resident water vapor to re-wet the sponge. It’s a one-way process. Any water that gets into the “atmosphere” gets sucked away by the vacuum