Snap Freezing

Denver

Penultimate Amazing
Denver
Joined
Sep 8, 2007
Messages
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There's a guy I hear occasionally lecturing about things that have influenced his life. He tells a story about a pond or lake, where a group of guys would come early in the morning. It would be cold, right around freezing, but the lake would be unfrozen. They would drop a 'seed crystal' in the lake, and it would freeze out from that crystal. He would relate this to how he likes to plant seed crystals today, in the form of ideas, and watch them grow and spread in society.

However, when I try to research this freezing phenomenon, all I can find are references to experiments about 'snap freezing', which seems to require a lab environment (very specific conditions, and very pure water). It seems pretty unlikely from my reading so far that a group of guys could be doing this with an outdoor pond, much less on a recurring basis.

Is there more to this seed-crystal thing than I have found? Or is this guy just telling stories?
 
As far as I know, super cooled water only exists in nature at high altitude in the atmosphere, in certain types of clouds.* There would be too many "imperfections" in the water for that to happen in a pond.

*supersaturation of water vapor (with respect to ice) at high alltitudes is fairly common and results in persistent contrail formation as the jet exhaust seeds the air.
 
Denver said:
There's a guy I hear occasionally lecturing about things that have influenced his life. He tells a story about a pond or lake, where a group of guys would come early in the morning. It would be cold, right around freezing, but the lake would be unfrozen. They would drop a 'seed crystal' in the lake, and it would freeze out from that crystal. He would relate this to how he likes to plant seed crystals today, in the form of ideas, and watch them grow and spread in society.

However, when I try to research this freezing phenomenon, all I can find are references to experiments about 'snap freezing', which seems to require a lab environment (very specific conditions, and very pure water). It seems pretty unlikely from my reading so far that a group of guys could be doing this with an outdoor pond, much less on a recurring basis.

Is there more to this seed-crystal thing than I have found? Or is this guy just telling stories?
Click to expand...
I don't know of a way to achieve that.
 
Denver said:
Is there more to this seed-crystal thing than I have found? Or is this guy just telling stories?
Click to expand...

Well, if the water is basically at the freezing point but unfrozen, and you drop in a bit of ice that's below freezing, it will grow when you drop it in. But the latent heat of condensation for water is pretty significant, so it's not going to grow all that much unless the temperature of the air is also dropping. The only case I can think of where any significant patch of lake would freeze is if the lake is going to freeze over anyways from dropping temperature, and putting some ice in just creates a specific starting point for that transition.

I once supercooled a cream soda by putting it in a freezer for a while. It was a glass bottle, and it was still liquid when I took it out, but when I popped the top off, ice crystals spread through the whole thing. Really cool, but it was only the pressure which kept it liquid, no such mechanism is available for the lake example.
 
It is a nice story. You should hear the "true stories" of some televangelists. Wonderful stuff. ;)
 
Ziggurat said:
Well, if the water is basically at the freezing point but unfrozen, and you drop in a bit of ice that's below freezing, it will grow when you drop it in. But the latent heat of condensation for water is pretty significant, so it's not going to grow all that much unless the temperature of the air is also dropping. The only case I can think of where any significant patch of lake would freeze is if the lake is going to freeze over anyways from dropping temperature, and putting some ice in just creates a specific starting point for that transition.

I once supercooled a cream soda by putting it in a freezer for a while. It was a glass bottle, and it was still liquid when I took it out, but when I popped the top off, ice crystals spread through the whole thing. Really cool, but it was only the pressure which kept it liquid, no such mechanism is available for the lake example.
Click to expand...

Bolding mine.

I suppose it is possible the guy in the story caused the nucleating event, but I think the growth rate of an ice crystal around a nuclei depends strongly on the degree of super-cooling. To get a noticeable growth rate, the water would have to be a long way below freezing. If that were the case, something else (dust, a falling leaf etc) would have nucleated the freezing long before he got there with his "seed crystal".

Impressive super-cooling with very fast crystal growth is, I think, only really accessible in the lab with pure water and good control of all of the nucleating surfaces.

ETA. As Ririon says, "It's a nice story, ;)"
 
Evilgiraffe said:
I suppose it is possible the guy in the story caused the nucleating event, but I think the growth rate of an ice crystal around a nuclei depends strongly on the degree of super-cooling.
Click to expand...

I'm not suggesting supercooling, but just ordinary freezing as temperatures dropped. Crystals will still grow from nucleation sites even without supercooling, just not as fast. But the story, as related, doesn't indicate the speed at which this happened. Maybe it took an hour or more. And maybe there were other nucleation sites.
 
Alferd_Packer said:
As far as I know, super cooled water only exists in nature at high altitude in the atmosphere, in certain types of clouds.* There would be too many "imperfections" in the water for that to happen in a pond.

*supersaturation of water vapor (with respect to ice) at high alltitudes is fairly common and results in persistent contrail formation as the jet exhaust seeds the air.
Click to expand...

Pretty much correct but super-saturated air can exist at low temperatures at ground level in the Arctic. One breath and you are surrounded by ice fog. :eek:
 
Supercooling isn't quite as lab based as you seem to think. It requires that the water be cooled down to anything between -42 degrees C and -10 degrees C (room pressure) and cooled in a stable environment (nothing moving/vibrating excessively) and the water contains no undissolved particles, such as dust particles, also including anything that may precipitate out.

It will then freeze when a large force or seed is applied.

It seems very unlikely that it could occur in a lake, but if you were to clean out a pond and refill it with spring or distilled water, it is possible.

Also, Ziggurat is right, I think the problem is the definitions of the time and what exactly constitutes this pond/lake.
 
The last time I heard the story, it was rather ambiguous: the setting was a "lake OR pond", and there was no information given on its size, or the time or scope of the freezing.
 
The story is bogus, but the effect is pretty easy to observe. Put a bottle of water in the fridge to get it very cold (and uniformly so), then put it in a bucket of salt and ice for another half hour. You might have to try multiple bottles if the mixture is too cold and the first freezes. At the end, very carefully open the bottle and drop anything in. The crystals grow very quickly, it's pretty impressive. Club soda works well for this too, and a corona in the freezer can do the job as well, assuming your freezer winds up being the right temperature.

In the winter, if you live in an area that freezes, you can do this extremely reliably by putting a case of bottled water on the porch on a night when the low is supposed to be just below freezing (mid to high 20's works well.) In the morning, before it starts to warm up, you'll have a whole case of water that is supercooled to play with.
 
Not that uncommon, apparently.

From NASA:

NASA said:
Three types of ice can form in a lake or pond. The kind of ice that forms depends on weather conditions.

1. On very cold, calm nights the surface water of the lake can drop below freezing. When ice crystals begin to form, they spread rapidly across the lake surface. The “c” axis of the crystals is vertical (up and down). Individual crystals can be a meter wide. This process is called Spontaneous Nucleation

2. When lake conditions are cold and winds blow dust, snow or frozen rain on the lake surface, Heterogeneous Nucleation occurs. This means that the dust, snow or frozen rain is a nucleus or center, and the lake ice crystals form around these centers. The lake ice grows with the “c” axis of the crystals horizontal.

3. Snow Ice forms when snow falls on ice and becomes wet and then freezes – becoming part of the lake ice. Snow Ice has very fine crystals and often looks white and isn’t clear.
Click to expand...
 
Denver said:
Is there more to this seed-crystal thing than I have found? Or is this guy just telling stories?
Click to expand...

This is probably not too pertinent, but I used to have an ice pack that had some gel-like stuff in it a plastic container with a Pringles-shaped wafer of metal. You'd put the thing in the freezer, but it never froze. Then you'd shape it to your aching joint or whatever, then flex the metal thing, and it froze solid instantly. Over 20 minutes or so it'd melt again, and you could repeat.

I have no idea what the material was or what the catalyst was or how it worked at all.
 
JoeTheJuggler said:
I have no idea what the material was or what the catalyst was or how it worked at all.
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My guess is it was probably water plus something to keep ice crystals from forming easily. The metal wouldn't have acted as a literal catalyst, but flexing the metal may have made it "snap", sending out a small shockwave which nucleated crystals. Am I right that the metal bit snapped when you flexed it?
 
JoeTheJuggler said:
This is probably not too pertinent, but I used to have an ice pack that had some gel-like stuff in it a plastic container with a Pringles-shaped wafer of metal. You'd put the thing in the freezer, but it never froze. Then you'd shape it to your aching joint or whatever, then flex the metal thing, and it froze solid instantly. Over 20 minutes or so it'd melt again, and you could repeat.

I have no idea what the material was or what the catalyst was or how it worked at all.
Click to expand...

Are you sure you have that right? There is a chemical called sodium acetate (the flavoring for salt&vinegar potato chips, oddly enough) that stays in a supercooled state, then crystallizes exothermically when you click a metal disc. It resets when you boil it for a minute or two. I've never heard of one that gets colder, but I'd be interested if there were one.

- Dr. Trintignant
 
Dr. Trintignant said:
I've never heard of one that gets colder, but I'd be interested if there were one.

- Dr. Trintignant
Click to expand...

Instant cold packs. A capsule of ammonium nitrate inside a water pack. Break the capsule and you get endothermic mixing of the two chemicals. Non-reversible though.

It's quite hard to find examples of spontaneous endothermic crystallisation as the massive loss of entropy associated with forming crystals is most easily compensated by raising the temperature of the surroundings. Hence, crystallisation is almost always exothermic.
 
Evilgiraffe said:
Instant cold packs. A capsule of ammonium nitrate inside a water pack. Break the capsule and you get endothermic mixing of the two chemicals. Non-reversible though.

It's quite hard to find examples of spontaneous endothermic crystallisation as the massive loss of entropy associated with forming crystals is most easily compensated by raising the temperature of the surroundings. Hence, crystallisation is almost always exothermic.
Click to expand...

Yeah, I've seen those, but it's hard to imagine one that's reversible by freezing and triggered by a metal disk. Joe probably has the two kinds conflated, but I'd be interested in being proved wrong.

I guess the ammonium nitrate reaction is endothermic because it starts in crystalline form and dissolves?

- Dr. Trintignant
 
I witnessed the same effect (on a smaller scale) in Iraq the first time. The platoon had gotten together and bought a couple deep freezes to put our water bottles in. When you go out to get one, they'd all be stacked inside, liquid. But when you pulled one out (or if you just tapped it) you'd see (and feel, if you were holding it) it freeze solid in about a second. Pretty neat.
 
I watched the top surface of a small pool of water freeze once. On purpose, even.

A large crystal would form in one spot; instantly disappear, and another would appear next to it. It was like a flashing on and off. Eventually, the "on" became more common than the "off" and the surface had a thin ice coating.
Quite fascinating, actually.
Though it must sound like a boring thing to do.
 
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