Why are changes of state physical changes?

1 Answer
Jun 11, 2016

Because changes of state do not involve the making and breaking of strong chemical bonds.


Chemical change is characterized by the making and breaking of strong chemical bonds, and the formation of new substances (I've said this many times before here; forgive me, I can never find the link when I need to use it). When card ice sublimes, or when water boils, the weaker intermolecular forces are disrupted, but the strong #C=O# or #O-H# bonds remain unbroken. Since the molecule remains inviolate, no chemical bonds are broken in a phase change, and the transition is properly regarded as a physical change. Capisce?