[miss_maple (OP)]

In which of the followings are the particles most disorderly packed ?
(a) ice & salt mixture at -10°c
(b)ice at 100°c
(c) water at 100°c
(d) steam at 100°c

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[lyner]

Can't imagine why there have been no replies to this, Miss_m.
The disorder you refer to is, I guess, easiest to describe as the temperature (average Kinetic Energy per molecule) - so steam would get it.

Anyone reckon different?

[Bored chemist]

Where do you find "(b) ice at 100C"?

[RD]

Surely a mixture of two substances is more disorganised than a pure substance in any state...

In terms of statistical mechanics, the entropy describes the number of the possible microscopic configurations of the system.

http://en.wikipedia.org/wiki/Entropy

So I think the answer is (a).
 

[lyner]

I suppose so. I guess steam comes a distant second, then.

[Bored chemist]

The ions which form the salt solution are surrounded by water molecules that are quite tightly bound. Since they can't move much their disorder is markedly reduced. In a eutectic mixture there's quite a lot of salt, so a fair fraction of the water molecules might be trapped this way.
The question isn't really well defined and I'd still like to know who asks questions about boiling hot ice.