* No new substances are formed: When sugar crystallizes, it's simply the sugar molecules rearranging themselves into a more ordered structure. The chemical composition of the sugar (sucrose) remains the same.

* The change is reversible: You can dissolve the sugar crystals back into a solution, returning it to its original state.

* No chemical bonds are broken or formed: The process of crystallization involves changes in intermolecular forces (the attractions between molecules) but not the breaking or formation of chemical bonds within the sugar molecules themselves.

In contrast, a chemical change involves the formation of new substances with different chemical compositions. Examples of chemical changes include burning wood (forming ash and gases) or cooking an egg (changing the protein structure).