Expanding Icecubes

The whole frozen robot thing got me thinking…

When you freeze most things they contract (shrink up). I work in the satellite industry (i’m only a artist/animator though) and there are big lists of how much any given material expands when heated in the sun and contracts when frozen in the earths shadow.

Anyway, thinking back to my childhood, I used to freeze my Han Solo toy in ice (ala Empire strikes Back) and the ice would expand (I think) and crack the cup it was in. Same thing with icecubes.

Does the ice break the rules and expand when frozen, or does the plastic of the cup or the icetray just contract more than the ice does?

Does the ice break the rules and expand when frozen?

Yes it does.
It’s one of the few (only?)compounds that does.

Man, I hate to do this, but here goes…

Actually, water freezes into ice, the ice doesn’t freeze. But, yes, water does expand as it freezes. And, anything that has water in it will do the same. Ever see milk freeze? I saw it often as a child growing up in Delaware. We still had milk delivery then, and we would often get up in the morning to find the delivered milk frozen, with a ‘plug’ of cream/milk protruding from the top of the milk bottle. Ahh, the memories…

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Jacques Barzun
Cheers! CAL

As water cools, it expands from 4°C to 0°C. This sort of behavior is unusual, but far from unique, especially among organic compounds.

Ice has a very open crystalline structure, with the molecules holding each other at arms length. Water itself is rare in that as a liquid, the arms-length crystalline structure is replaced by random, fluid, temporary closeness between molecules.

I don’t really remember the chemical reason for this. Some possibly associated reasons are the strong dipole moment in a water molecule - the oxygen end has a negative charge and the hydrogens have a positive charge. This provides a lot of “incentive” for the molecules to stand off from one another if their Brownian motion is low enough. When the motion gets too high, the structure is broken.

I liken the situation to one of a meeting of a bunch of very stiff people. They meet and shake hands, and fill up a lot of space, too shy to move around much. Then something breaks the ice (not a pun - an analogy!), and they start being more comfortable with each other, and less defensive about their personal space. They move past each other more easily, despite being more densely packed. When the energy wears off, they get shy again.

But then, I really love chemistry analogies.

Yeah, what Boris said. :slight_smile:

When water freezes, it forms a crystalline structure in which there are 4 hydrogen atoms keeping close to each oxygen atom, but of course these hydrogen atoms try to keep as far from each other as possible.

Perhaps we could liken it to group sex with major homophobes. :wink:

Only if the group sex includes twice as many men (hydrogen atoms) as women (oxygen atoms), and the women are all much bigger than the men. Like Amazons at a hobbit convention, perhaps.

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It’s a good thing that water expands when it freezes. If it didn’t, ice would not float, it would sink. That’d cause all kinds of problems with life as we know it.