# Molecules of a solid [closed]

Question: Molecules of a solid :

(a) are always in a state of motion

(b) move only when heated

(c) move because they are loosely bound

(d) do not move at all

My attempt:

I could safely ignore (c), as molecules in a solid are tightly bound. My book says that molecules in a solid vibrate about their fixed position. But they also expand on heating. Due to this, I am totally confused whether the correct option (a) or (b) (or maybe (d)?)

I know the question I am asking is really basic, and maybe does not even belong here, but I searched many sites and none revealed satisfying information. And thus, I am looking for expert help. I even doubt if my book (from where this question is) is correct or not.

Thanks a lot.

## closed as off-topic by John Rennie, Dilaton, jinawee, tpg2114♦, Kyle KanosFeb 22 '14 at 18:06

This question appears to be off-topic. The users who voted to close gave this specific reason:

• "Homework-like questions should ask about a specific physics concept and show some effort to work through the problem. We want our questions to be useful to the broader community, and to future users. See our meta site for more guidance on how to edit your question to make it better" – John Rennie, Dilaton, jinawee, tpg2114, Kyle Kanos
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• Clue: the atoms in liquid helium move even at absolute zero due to zero point energy. – John Rennie Feb 22 '14 at 12:42
• @JohnRennie So, it means that the answer is (a) ? Because if the liquid helium moves, then solids could also. I am sorry if I got it wrong because my physics level is really low. – Gaurang Tandon Feb 22 '14 at 12:46
• Though your teacher might not know about zero point energy, in which case the answer would be (b). – John Rennie Feb 22 '14 at 12:49
• @JohnRennie I really don't understand why the concept of zero point energy required in a class 8th book question. Could you please explain why is the answer (b) in a bit more plain language. Thanks. – Gaurang Tandon Feb 22 '14 at 12:56
• The question is a little vague. I look at option (b), and assume that by "heated" the questioner means heated in an oven or a bunsen burner ... that is, starting at room temperature. From that I take the solid in option (a) as being at room temperature, and I think that's a reasonable assumption for an 8th grade science question. But as I said, the question is vague. Hope that helps a bit! – garyp Feb 22 '14 at 14:12

Buckminsterfullerene, ${C_{60}}$, is a very slippery ball. Despite its (lattice) high melting point, each molecule freely tumbles in plaice within the crystal lattice. This is seen by the disorder in its crystal structure (atomic positions cannot be resolved). More telling, a C-13 NMR of the solid (no magic angle spinning) shows sharp lines as a solution spectrum would.