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Question 13 from the ACS chemistry olympiad exam:

The phase transition from gas to solid is called \begin{align} &\text{(A) condensation.} & \text{(B) evaporation.} \\ &\text{(C) polymerization.} & \text{(D) sublimation.} \end{align}

I am pretty sure the answer is deposition, which is not listed, but yet the answer is (A) condensation [scroll to the end of the question paper to see the answer key].

Did the chemistry olympiad make a mistake, or is there something obvious that I am missing?

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I guess the diagram of phase changes you have in mind looks like this:

enter image description here

Indeed this says deposition is the right name for a gas-to-solid phase transition and I believe that this is the only correct term.

The only thing I can argue why it is obvious here that condensation is the right answer (at least the closest) is that this is the only answer that gives a transition from fluid to solid. B and D are the other way around, and C is not really a phase change (although it could result in one).

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    $\begingroup$ Good point concerning the condensation as the only "real" phase change in a classical sense. $\endgroup$ – Klaus-Dieter Warzecha Mar 17 '14 at 8:04

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