I was having a glass of wine over candlelight and I noticed that the liquid wax was completely transparent but turned opaque when when the wax solidified. Why does this happen? Clearly, when the molecules reorganize during the freezing phase transition they begin to interact with the light. What intermolecular changes bring this about? I know this can also happen with water but I'm not sure it's for the same reason because the most organized ice is clear. Only when the crystalline structure is disturbed (the ice is fractured, aerated, etc.) does the solid water become opaque. So it seems that the transparent liquid to opaque solid transition in water is due to repeated diffraction and scattering, leading to reflection. The same thing has to be happening in the wax (i.e. repeated diffraction-scattering) but I can't figure out molecularly how the phase would effect this. I froze some cooking oil (sesame seed) and found that the same phenomenon occurred, which leads me to suspect that it has to do with the ordering of the aliphatic hydrocarbon tails. Any thoughts?