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Is there a scientist in the house?! A question...?
Posted by: RAMd®d
Date: March 13, 2019 09:25PM
How does one get a test tube half filled with water (H2O) to 20ºF without it freezing?

I was watching a program about rain, and the above was part of a demonstration. But there was no mention of how to chill it without freezing it.

The tube was held with tongs in ambient air, and the person holding it wasn't wearing gloves. It appeared to be a typical lab environment.




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Re: Is there a scientist in the house?! A question...?
Posted by: TheTominator
Date: March 13, 2019 09:28PM
Sounds like it was "super cooled".

Start with very pure water that has no minerals or other imperfections that would serve as nucleation sites for ice crystals to form.

Chill it undisturbed for a few hours.



Edited 1 time(s). Last edit at 03/13/2019 09:31PM by TheTominator.
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Re: Is there a scientist in the house?! A question...
Posted by: pdq
Date: March 13, 2019 09:48PM
Oddly enough, many years ago we rented a house that had a malfunctioning refrigerator. I soon discovered it was the place for beer in the summer. The beer cooled in this refrigerator was _so cold_ it was supercooled; when in the bottle, it was liquid, but when you opened the bottle and released the pressure, ice would often form precipitously. Sometimes a little ice (the coldest, most delicious cheap beer you’ve ever had!), and sometimes the entire beer would woomf! - turn into ice instantaneously (which was not as useful.)

Anyway, one way to supercool water (or beer, at least) is to pressurize it while cooling, apparently.
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Re: Is there a scientist in the house?! A question...?
Posted by: RAMd®d
Date: March 13, 2019 10:48PM
Start with very pure water that has no minerals or other imperfections that would serve as nucleation sites for ice crystals to form.

Yes! Thanks. It was mentioned that earlier in the program that ice won't crystalize unless it has something attach to – micro meteorites, life forms, etc. I didn't think about it and it wasn't mentioned when the test tube was presented.


Anyway, one way to supercool water (or beer, at least) is to pressurize it while cooling, apparently.

The alcohol in the beer must keep it from freezing (under pressure!) at least. When I chilled a bottle of sparkling cider it froze, to its cost.




When a good man is hurt,
all who would be called good
must suffer with him.

You and I have memories longer than the road that stretches out ahead.

There is no safety for honest men
except by believing all possible evil
of evil men.

We don’t do focus groups. They just ensure that you don’t offend anyone, and produce bland inoffensive products. —Sir Jonathan Ive

Perfection is the enemy of progress. -Winston Churchill

-An armed society is a polite society.
And hope is a lousy defense.

You make me pull, I'll put you down.

Mister, that's a ten-gallon hat on a twenty-gallon head.

I *love* Sigs. It's Glocks I hate.
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Re: Is there a scientist in the house?! A question...?
Posted by: Speedy
Date: March 13, 2019 11:56PM
Quote
RAMd®d
How does one get a test tube half filled with water (H2O) to 20ºF without it freezing?

I was watching a program about rain, and the above was part of a demonstration. But there was no mention of how to chill it without freezing it.

The tube was held with tongs in ambient air, and the person holding it wasn't wearing gloves. It appeared to be a typical lab environment.

The person holding the tongs must have been very, very still. Hard to believe it was at 20°F.



Saint Cloud, Minnesota, where the weather is wonderful even when it isn't.
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Re: Is there a scientist in the house?! A question...?
Posted by: NewtonMP2100
Date: March 14, 2019 06:32AM




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Re: Is there a scientist in the house?! A question...?
Posted by: SKYLANE
Date: March 14, 2019 10:58AM
Us pilots know about super cooled water too and it’s dangers if you don’t have deicing or anti-ice equipment on the plane.

[en.m.wikipedia.org]
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Re: Is there a scientist in the house?! A question...?
Posted by: Carnos Jax
Date: March 14, 2019 04:52PM
Yeah, you're plane functions as a huge nucleation site.
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Re: Is there a scientist in the house?! A question...?
Posted by: freeradical
Date: March 16, 2019 02:12AM
This thread made me go look at a temperature versus pressure phase diagram chart for water.

Very interesting...
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