How does the second law of thermodynamics relate to crystal formation?

Answer 1

Short answer: the 2nd law of thermodynamics applies only to closed systems, and the only truly closed system is presumably the entire universe (if even that). Crystals always form in the context of a larger system providing energy, meaning that entropy increases elsewhere, proportionate to the decrease of entropy represented by the crystal formation. Here is a somewhat more in-depth answer:

http://www.newton.dep.anl.gov/newton/askasci/1993/chem/CHEM047.HTM

Answer 2

The second law of thermodynamics states that in any spontaneous process, the entropy of the universe increases. In crystal formation, atoms or molecules arrange themselves into an ordered structure, reducing the overall entropy of the system. However, the formation of crystals usually involves an increase in entropy in the surrounding environment, allowing the process to be spontaneous and consistent with the second law.

Answer 3

One formulation of the second law is that the change in Gibbs free energy for any spontaneous reaction will be positive.

Answer 4

A chemical reaction is only possible if total entropy increases.