Supercooled Water: Newsletter Challenge (May 2014)

I am going to give this a good answer as this best explains it as far as I understand it. It's the lack of nucleation.

Thank you, AH. I can't claim much credit because it's one of those things I read about somewhere on CR4. It may not be the desired answer (ain't heard no fat lady singin'), but it gives a pointer to those inclined to home experimentation. I'm still in the doghouse after my last tinkering

Did that middle experiment and made a video. It's real easy. Make a 2450 MHz resonator from a 61 mm dia tinfoil disk and a 30 mm finishing nail up thru the center. Put a shotglass of water in one corner of the oven to keep from frying the magnetron. Put a *Pyrex* bowl over the resonator to contain the plasma. Make *sure* to use Pyrex, specifically, as some other types of glasses can melt in a microwave oven due to thermal runaway.

At resonance, the electric field at the tip of the nail exceeds the breakdown voltage of air by a wide margin and so you get a hot arc at the tip which slowly vaporises it, making the nail grow shorter. When it gets too short it no longer resonates at the oven's frequency, and the arc extinguishes. When it's too long or too short the center of the nail will glow red-hot due to the induced current. Electrically, the thing is a Tesla 'coil' except that it works at microwave frequencies.

That shotglass of water should keep you out of the doghouse but, still, it's better to experiment when the missus is away. They don't like us menfolk messin' with their stuff.

Now this is what keeps CR4 fun. A question leads to some chat, and then we get to the naughty-but-fun stuff.

It's just occurred to me that I'm not sure how to ID Pyrex. Honest to hooty, I just use stuff with reckless disregard. When you buy glassware for kitchen use, it usually states on the packaging what it's safe to use in (microwave, dishwasher etc). Cripes...I enjoy cooking, but I'm not going to do this every time I pull out a dish I haven't seen before !

It'll say 'Pyrex' on the bottom. It's a brand-name as well as a specific kind of glass. Other glasses labeled 'microwave safe' may be safe under ordinary kichen circumstances, but I wouldn't count on it in this app. We're pushing things to the edge, EM-field-wise.

"Whatcha makin' dear?"

"You. Mad."

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ps: not enough bandwidth here to play that vid.

Stoves by Lucas Electric?

Or even....

No pic, señor squirrel. :(

Wah !!! Some scent that uses the slogan 'cool water', and has a rather nice picture to go with it.

Oh boy....in the cups again he is....

Now THAT is a supercool squirrel.....

You can have a look at the phase diagram pressure-temperature of water:

AKA 'Prince of Darkness'

Although far from scientific, this may explain why the unopened bottle of water I had on the dash of my truck had no ice whatsoever after being motionless for 12 hours at single digits F. It only reached 15 F that day, and had no ice the following morning with single digit temperatures all night. On the 3rd day, which was slightly warmer, it was frozen solid. I was wondering "What the heck is in that water?", when perhaps it really was just pure water.

It does not have to be "ultrapure" in the sense of no solutes, can have solutes, but no particles suspended in the colloidal state whatsoever. This is a characteristic of "RO" treated water, the particles are removed to a very efficient degree.

It's water that can't decide where to start freezing first.

Water, it turns out, is reluctant to freeze. Ice crystals prefer something to form on - a particle of dust will work, or a rough surface. The scientific team found that dust-free water on a smooth, clean surface will drop well below 32 Fahrenheit (zero Celsius) before it freezes. In this state, the water is called "supercooled." But once one crystal does form, the supercooled water will freeze rock-solid in an instant.

Despite what you may have heard, water doesn't always freeze at 32 degrees Fahrenheit. A team of scientists in Israel has come up with a way to control the temperature at which water will freeze.

I've looked at some of the replies, but I have not researched "supercooled water" and have not come across information on this particular phenomenon at any time in my life.

I am testing my understanding of chemistry and physics here, so if I am completely off, please be gentle.

• IF the water is pure enough
• AND IF the container has a wetted surface that is smooth enough and nonreactive to water at Standard Conditions
• AND IF (at Standard Conditions), the hydrogen-bond energy is the same between water-water interactions and water-wetted surface interaction
• THEN water molecules will not know where to start the crystallization. Hence the lower temperature before crystallization will be observed.

OK - I'm finished. Now I want to check it out and see how horribly wrong I've got it!

Agitated water can be cooled to about 14 degrees F, but as soon as the agitation stops it will freeze into a solid block quite quickly. By agitated I mean in constant motion.

Why a mountain stream first freezes at the edges.

moving water doesn't freeze (if the temperqture of the environment is not too deep)

the water molecules have no time to fetch the massive ice shield around them!

There are some medium molecular weight water soluble polymers that also interfere with the freeze point of the solution in water (along with other solutes). The known freeze point turned out to be approximately -10°C, but the solution readily supercools to -15°C or thereabouts with little problem, no agitation, just a clean glass test tube, no particular filtration to remove any nucleation particles. Scratch on the side of the test tube, even with a polished glass rod, and freezing instantly takes place with temperature resolving to the "normal" freeze point.

Back to the original question: Removing all filtrable particles helps prevent nucleation, motion helps, but must be without causing any cavitation or high frequency sound waves, removing dissolved gases might help, but most gases increase solubility at lower temperatures, thus any other critical behavior is not likely.

I heard a report of a 1:1 glycol-water mixture stored in barrels in Alaska that supercooled for nearly 20 years! The temperature of storage never went above the known freezing point of the mixture, but without any intervention, at some late point in time did in fact freeze. The reported normal freeze point is near -50°F.

the atomic structure of the water molecule.

salt and other ingredients; ever seen snow on the road!

The OP was not talking about freezing point depression, but rather the observable of liquid water being present well below the expected freezing temperature. This is rarely if ever seen in "nature", but is possible quite readily in a laboratory setting.

Of course, I forgot to mention that for some (possibly including me), the world is a giant laboratory.

Liquid water below the "freezing point" happens quite often and is the cause of ice storms. Ice crystals formed in the clouds melt as they fall through overrunning warm air below the formation layer then become super-cooled as they fall through a shallow layer of below freezing air at the surface. If the layer of cold air at the surface is too shallow the drops won't cool sufficiently to freeze upon impact. If the layer is too deep the drops will freeze before impact and become sleet. Just right and you can rapidly build up several inches of ice on objects. Meteorologists and pilots generally are concerned about super-cooled droplets at temperatures between 0C and -25C but in the right conditions a droplet can remain liquid down to almost -40C.

the question was for liquid water, not the way it is liquid

In small hydroelectric projects, one system owner thought that his 4" diameter water line had "Frozen for winter" and it had not reached above 0F for several days. To his surprise, the system started flowing water again, even with the temps hovering between 0 and 15F during the day.

His assumption was that higher water pressure allowed the water to flow without freezing in the piping.

Looking at your answer, I am wondering if distilled or reverse osmosis pure water might have a lower than 30F freezing point, or if pressurized water will change it's freezing point.

Most engineers realize that by adding enough salt, that 0F is achieved before ice will form. We have HVAC systems at work that routinely run at 15-20F without freezing due to the amounts of chemicals added to the system to prevent freezing. But of course this is not "Water" but "Treated water / glycol mixture".