Re: [Phys-l] sudden Vacuum freezing

["fred bucheit" <fbucheit@hotmail.com>]

Years ago I needed some ice for an experiment the following day in Physics 
class. I placed some water in a standard ice cube tray (back then it was 
aluminum with a removeable aluminum divider) and left for the day. The next 
morning I opened the freezer compartment of the refrigerator and pulled out 
the tray. To my disappointment, the water did not freeze. I decided to pour 
it down a drain on the other side of the room. As I walked across the room I 
happened to look at the tray and I thought I saw something moving in the 
water. It was then I realized that it had supercooled and I was watching the 
crystallization of the water. How many times in a lifetime does one see that 
by accident?

Fred Bucheit....retired

~I think is the antidote to I believe~



> Hi,
>
> 	For our final lab for or sophomore physics majors, we try to show them
> some odd things like rattlebacks.  We show them how to freeze water in a
> vacuum.  One uses a shallow dish (1/2 inch of water) on a good insulator
> in a vacuum belljar. and start pumping. (This is hard on the pump.)  The
> vapor pressure drops, and the water boils.  The water cools to its
> freezing point  with the removal of thermal  energy.
>
> 	I saw something surprising, at least to see.  The water supercooled,
> and while I was watching it froze in about a second.  It was slow enough
> that I could see a the water-ice boundary move across the dish like
> almost like a wave.  The dish was then frozen to at least half of its 
> depth.
>
> 	I understand what happened, but am amazed that the water was
> supercooled to a temperature such that so much water would freeze, and
> that I happened to be looking at the right moment.
>
> Thanks
>   Roger Haar
>    Physics U of AZ
> _______________________________________________
> Forum for Physics Educators
> Phys-l@carnot.physics.buffalo.edu
> https://carnot.physics.buffalo.edu/mailman/listinfo/phys-l

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