Properties of Water

Re: Properties of water:

Look for a chart or formula that gives the boiling points of water at various pressures. Water will boil at very low temperatures under vacuum conditions. The old story that if an astronaut's space suit was holed sufficiently, his blood would boil. There's a space experiment to suggest to NASA for study: What happens, time wise, to 100 gm of distilled water when suddenly exposed to the vacuum conditions of outer space?

The small quantity would instantly 'explode' into a fine mist/fog/haze (assuming it was not in a container of some kind.) If it were in a can, there may be a layer of ice dust on the bottom for a short period until it all sublimes. Depends on thermal mass of container wall. The operative word is 'suddenly'. Is that really instantaneous-a theoretical condition.

Explosively is not quite the proper description, but close enough. The vapor pressure throughout the liquid will rip it apart nearly instantaneously, limited only be inertia of the mass.

Good point, Gwen.

The key is "suddenly". If that is very, very quickly, we wind up with some collection of much smaller frozen drops, like the urine dumps from the shuttle. And, those do require energy.

Hi, Gavilan!

There is a lot of space ice out there, largely due to the lack of warmth in "outer space". I have a feeling that your water would not so much be subject to additional heat and vaporization as heat loss into the vastness of space, and ice right up.

Mark

On the same subject, what will happen to the human body if suddenly exposed to a full vacuum ie. thrown out of a spaceship? Will all the liquid in the body want to turn into super heated steam in an instant?

The water in places like the nostrils would flash, though it wouldn't be superheated steam, but, rather, cold steam. In most places, the bodily membranes should remain intact (the differential depends on the spaceship design but will certainly be less than 15 psi).

Although we probably don't have the straight story, the Soyuz 11 cosmonauts were exposed to a fairly low pressure and returned looking pretty normal (like a scene from Benny Hill, the Russians apparently thought they were "only sleeping").

I once heard the suggestion that, in a vacuum, every drop of water in the body will in an instant turn into steam and will thus tend to blow every cell to smithereens, especially with some body heat available.

Any comments?

It would be correct to refer to it as "super heated steam," wouldn't it? Doesn't "super heated," as used, refer only to the heat of the water in relation to its environment. That is, even if quite close to absolute zero, if the liquid water has more heat than is required for it to boil, it is "super heated."

Just my steeply discounted 2 cents.

definately would hurt...nostrils, eyes and lungs (any air/water interface) would get frosty from the moisture evaporation.

Air embolism (what happens to scuba divers that surface too quickly) would ensue as the dissolved gases in the blood stream suddenly return to gas form.

I'd rather not think about the sinus headache that would come (since I've got a cold right now) but I sure hope whoever decides to jump out of a spaceship will jump right back in quickly!

I hope he tought of a rope to pull himself back in.

I believe the heat comes from the latent heat in the water that in a vacuum exceeds it's boiling point.

"If one gram of water at one atmosphere at 50 degrees C is suddenly exposed to the vacuum of free space, what happens to it?"

IIRC POOF. This was done with a large vacuum bell jar in high school physics lab. Since it was at room temperature any differences between lab and space would be somewhat pronounced in favor of rapid if not instantaneous sublimation of any ice particles.

Has anyone observed or tried the experiment with near space conditions? Without experimental observations, the results to be expected are educated guesses.

I wish I had my lab at the school I used to teach in. I would put this together and report on the results this afternoon. The setup would be simple. Pull a near perfect vacuum on a large bell jar connected to a smaller bell jar (with a small beaker of water...of course) with a tube and valve. Open the valve quickly and see what happens. Before I read your post, Stirling Stan, I was thinking of how this experiment could be done.

Anyway, is there anyone out there with a lab setup who could do this? If so, let us know.

DAG: Running an experiment to simulate the conditions of space beats a multitude of WAGS or opinions.

Indeed. I did a web search to see if I could find any video of such an experiment, but came up empty handed. Such an experiment would be great for the science classroom!

Hi, Stan!

The so-called "conditions" of space being produced in a bell jar ought to include appropriate temperature environments as well so that the net effect is closer to the actuality of what might occur in 'space', as we wags like to assert in our various opinions. <------very cool wag

If the NASA folks and the Russian Cosmonaut program have to employ 'sublimators' to dissipate their liquid waste, perhaps that's because the liquid waste just doesn't dissipate so well without a little help.

Mark

So when we say vaporize, is this just reduction of primary mass or molecular separation?

How about sublimation? Can we call cavitation a near perfect vacuum?

Tomqwest

It vaporizes more than likely.

The reduction in pressure is the driving force and would be fairly instantenous.

Since the pressure is effectively zero, even if ice did form, it would quickly sublime due to the lack of pressure.

The heat is from the heat capacity of water since its at 50 C

Final density would be infinately small since it is in space and there would be nothing to contain the expansion.

Thank You Everyone for your thoughtful answers but I am still more than a little confused. Please be patient.

The specific heat of water is 1 calorie per gram per degree centigrade.

The heat of fusion about 80 calories per gram

The heat of vaporization about 540 calories per gram.

Since the one gram of water is at 50 degrees this gives 50 calories of energy from the available specific heat and 80 calories available from the heat of fusion for a total of 130 calories. This would provide enough energy to vaporize slightly less than .25 grams of our 1 gram water sample, leaving .75 grams of water in the solid state.

Could sublimation occur without an additional (.75 * 80) + (.75 * 540) calories of energy? or is only the (.75*540) required?

Once the water has vaporized in the vacuum of space, would it have a tendency to remain a cloud or dissipate?

Someone used the term "disassociate" in their reply. Kind of a silly thought, but would it be possible to disassociate the hydrogen and oxygen by super fast evacuation in the presence of adequate heat = heat of vaporization + bond energy?

Example; placing our one gram sample of water in a very small volume that is physically connected, but isolated by a super fast valve, to a super evacuated large volume, then under the illumination of a high flux laser frequency that corresponds to best absorption frequency for water vapor, open the valve? Would the molecule disassociate and then immediately re-associate? How about if there was also present a very high electrostatic field that would draw the Hydrogen and Oxygen away from each other? I understand it would be a high energy intensive method of disassociation but who knows what else might be learned?

Certainly this has already been tried.

Gavilan

Hot Dang, Gavilan!

Suddenly I feel like I'm in an engineering forum again. Can hardly wait until this topic hits the next level. Thanks for your creative energy.

BTW, still think that you're going to end up with a little chunk of (integral, not separated, not sublimated) space ice. The heat properties posessed by the droplet will no longer belong to it, and it will not be disassociated or ex/imploded by exposure to vacuum. Instead, the calorific value of this drop of water will be altered by the ambient temperature, and bingo! Ice--a contiguous group of crystals by nature. Admittedly, the cooling will be rapid, but since it will not be influenced by a body of cold temperature coming into contact with the droplet at a single point and causing dissimilar temperatures to occur within it, there is very little likelihood that it will undergo sublimation or disassociation. The net heat losses will remain calmly at zero as the substance of space equalizes out its meagre calories with the droplet until it has completely crystallized.

Mark

Mark,

Thank you for your reply. There is one part of your reply that I found most interesting.

"Instead, the calorific value of this drop of water will be altered by the ambient temperature, and bingo! Ice--a contiguous group of crystals by nature."

Given the vacuum of space as the environment; it seems intuitive that a small amount of the water would indeed vaporize until there was no further enthalpy to continue the vaporization process. Once the specific heat and heat of fusion had been used in vaporizing that small part of the water droplet, the rest would be frozen and would remain frozen until some source of energy was made available to allow sublimation to occur. In space this sublimation energy could be supplied from the radiation of the Sun or even the radiative output of a nearby object, or in the case of low earth orbit, the radiative flux of the earth. It seems reasonable that there would be no other means for vaporization heat to be transferred to the ice, allowing sublimation to occur, except via radiation because conduction and convection cannot occur in space.

If given no outside radiative input, would the ice continue radiative cooling until it's enthalpy was equal to that of the space around it?

Is there even such a thing as the enthalpy of space? If so and then how ever small it may be, would it vary as the distance from the sun increases? At what rate does it decrease? Inversely as the square of the Sun distance? The cube of Sun Distance?

What type of experiment could be used to determine that value?

Gavilan

Hi, Gavilan!

"Once the specific heat and heat of fusion had been used in vaporizing that small part of the water droplet"

Interesting thought. Vapourizing to where, though? Using the energy of evaporation somehow induced by this rapid boiling thought posted above? Or perhaps just next to the forming ice and becoming a part of it, if indeed any vapourization is possible in outer space where stassis reigns instead of moisture, atmosphere and gravity.

The enthalpy of space has to be quite small, and probably depends upon cosmological body radiation (all esoteric theorizing about 'dark matter' aside). The heat loss from the water will be more pronounced.

Imagine shooting a stream of cool steam into outer space. Any naked gas dissipation aside, the water droplets would most likely freeze up and form a trail of ice crystals of various sizes. Is that somehow to be regarded as sublimation?

Now, on a larger scale, and with a relatively lower and irrelevant temperature difference from the cool steam, consider the cc of water.

Imagine placing a cc of water into the same milieu... kind of like an instant vacuum jar, but at extremely low temps with no beaker to hold the water, no atmospheric pressure to hold the meniscus, no gravity to hold it in place, and no gradual formation of the vacuum. Can it boil when there is no gravity-held surface to allow water molecules to escape from it? Perhaps it will use its own tiny gravity to try to escape from itself. Will it fly apart or sublimate (and if so, where will the ice crystals form..or will they just move on coldly and invisibly forever looking for a surface)? All of these possiblities are exciting, but I think the reality is much more mundane. The water will rapidly lose its heat, just like it would if suddenly exposed to severe cold temperatures on earth, and the end result can more be described as "plonk" when it hits the ground than "Whizzzzz" on the way down (except in this case of course, there is no ground to hit!).

Mark

I suspect there is an experimentally determined answer out there. The astronauts/cosmonauts use sublimators (or some call them desublimators for some unknown reason) to dump excess water and those must have been tested. There are lots of NASA reports dealing with sublimators, but I've found no descriptions of this particular question yet.

The Russians, if I remember correctly (a real shaky proposition anymore), sort of did this experiment. They apparently used a sublimator in a soft vacuum and froze big clumps of ice. I don't recall the details and don't know how to find them easily; any Russian members out there?

I do an experiment like this in vacuum class, during the first week. The big difference for me is that as soon as you expose the water to the vacuum you no longer have an outer space like vacuum. My vacuum pumps are not fast enough to keep the vacuum in the lowest pressure regime.

What I do see is sudden rapid boiling of the water with rapid temperature reduction, followed by reduced boiling at the water temp goes down, until an ice cap is formed. Since I work in a gravity environment, I have to contain the water. The container acts as an insulator to some degree. The water does freeze from the surface that is giving up its heat to the molecules of water changing state becoming a gas.

Once you have an ice cap on the water, the process slows way down. Sublimation removes heat at a much slower rate than boiling.

In outer space if the water was not contained, I believe that the rapid boiling of water from the instantly reduced pressure would cause the water to disassociate into very small droplets. I think these would dissipate quickly into nothing you could see.

Water boils very intensely when vacuum is first applied to it. A One liter water bottle will boil over if more than an inch of water is in it when vacuum is applied. Vacuum Pumps really don't do well with water in them.

The OP specifies one gram of water. That is only one cc which is a pretty small amount. A large bell jar would offset some of the lack of capacity of the vacuum pumps.

I had some experience with three 36" oil vapor diffusion pumps with commensurate sized mechanical fore and roughing pumps to maintain plasma operating conditions in a huge vacuum tank of something like 40 cubic feet. Once outgassing and glyptal sealing of leaks on the new tank was accomplished only one diffusion pump was required and it was throttled to about 15 - 20% of capacity. SOME BELL 'JAR' THAT! Almost enough to qualify as outer space conditions.

Dear GAVILIAN

Greetings from EGYPT

If any liguid is succenly subjected to excessive vaccum it will sufer a sudden drop in inthalpy, ie adrop in its interrnal energy, so, its volum will expand thdoughly and its temperature is reduced. This is what we call FLASHING. The energy of expantion is obtained from the internal energy of water, which reduces its temperature. The suration of this process may be in milliseconds, while the traces of water molecules can not be found

PUMPMAN