Which of the following is an example of a physical change? MCQ with Answer and Explanation

Melting of wax is a physical change because it involves only a change in state from solid to liquid without altering the chemical composition. The wax remains the same hydrocarbon mixture. In contrast, rusting of iron (Fe₂O₃·xH₂O formation), burning of magnesium (MgO formation), and digestion of food (enzymatic breakdown into simpler molecules) are chemical changes where new substances are formed. Physical changes are reversible, while most chemical changes are irreversible. Exam tip: Remember, changes of state (melting, boiling, condensation) are physical changes unless a chemical reaction accompanies them.