

It Takes 275 Water Molecules To Make Ice - co_pl_te
http://www.scientificamerican.com/podcast/episode.cfm?id=it-takes-275-water-molecules-to-mak-12-09-26

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andrewcooke
this is explained a lot better at <http://www.mpg.de/6362003/water-ice-
crystal> :

 _In ice crystals, the water molecules arrange themselves in a six-sided, or
hexagonal, to use the scientific term, spatial lattice. Each water molecule
forms chemical bonds, so-called hydrogen bonds, to four adjacent molecules.
This honeycomb crystal lattice of water ice requires more space than liquid
water, which is unusual. As long as the water clusters have not reached the
minimum size for a crystal, the Göttingen experiment presents them with a
dilemma. The experiments take place at around minus 180 to minus 150 degrees
Celsius - the molecules are therefore much too cold for a liquid. For a
crystal, however, they are still too few in number. The tiny clusters escape
this quandary by forming a type of liquid that has clotted in the cold: they
form a rather disordered, “amorphous” spatial lattice._

 _If the cluster now grows, the water molecules at its core can change at some
stage from the disordered chemical game into the crystalline structure by each
of them taking four neighbours by the chemical hand. 275 water molecules thus
create the initial beginnings of a real ice crystal with hexagonal structure
in the interior of the cluster. To begin with, this structure is still
slightly deformed; however, as the cluster grows in size, this interior grows
to become a nicely ordered ice crystal, while the outer layers remain
amorphous. “When there are 475 molecules, the very core is already perfect,”
says Buck._

also, [http://physicsworld.com/cws/article/news/2012/sep/21/how-
man...](http://physicsworld.com/cws/article/news/2012/sep/21/how-many-water-
molecules-does-it-take-to-make-ice)

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Jabbles
Irritating headline (and summary) makes it sound like some kind of hard number
at which ice (starts) to form. The abstract states " _Spectral features
indicating the onset of crystallization are first observed for n = 275 ± 25_ "

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koide
The uncertainty coming from the spectral analyzer and not from the water
itself, I expect.

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Retric
It's probably both. What there looking for is an optical change which only
indirectly relates to if something is 'ice' or not. And I suspect depending on
which part's of the lattice are missing and where the light source is would
change the optical property's.

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bkanber
The subtitle of this article irks me:

> the change to ice occurs at 275 H20s.

That's a zero, not the letter O, in "H20s".

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stephengillie
So a body of water won't turn into ice if the body of water has only 274
molecules?

Can we make a kind of "ice-steam" of below-freezing water molecules suspended
in air or another medium?

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JoeAltmaier
Can do that anyway, with any amount of water: put it in a vacuum. It vaporizes
and freezes at the same time.

~~~
stephengillie
True, but water can still clump in a vacuum

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xsace
So where is the picture?

~~~
jonsen
Link in comment:

[http://physicsworld.com/cws/article/news/2012/sep/21/how-
man...](http://physicsworld.com/cws/article/news/2012/sep/21/how-many-water-
molecules-does-it-take-to-make-ice)

------
blerrrgh
A general had a problem: mud. Marines have slogged their way through it for
generations. Is it possible to get rid of mud? Without having to carry
anything heavy? Marines already have enough to carry.

Dr. Felix Hoenikker, an original thinker, found the "outside-the-box" answer;
a single crystal of Ice-Nine would crystallize every bit of water it touched.

"...suppose, young man, that one Marine had with him a tiny capsule containing
a seed of ice-nine, a new way for the atoms of water to stack and lock, to
freeze. If that Marine threw that seed into the nearest puddle...?"

"The puddle would freeze?" I guessed.

"And all the muck around the puddle?"

"It would freeze?"

"And all the puddles in the frozen muck?"

"They would freeze?"

"And the pools and the streams in the frozen muck?"

"They would freeze?"

"You bet they would !" He cried. "And the United States Marines would rise
from the swamp and march on!"

~~~
terhechte
I had to think about the same book when I read the title (Cat's Craddle,
Vonnegut)

