The burning of a magnesium ribbon is a classic example of a chemical change (combustion) where magnesium reacts with oxygen to form magnesium oxide. This reaction is highly exothermic, releasing a significant amount of heat and bright white light. Melting wax, boiling water, and sublimation of camphor are all physical changes. They involve changes in the state of matter but do not produce new substances or typically release both heat and light in the same manner as a combustion reaction.