Which of the following is/are the example/examples of chemical change? 1. Crystallization of sodium chloride 2. Melting of ice 3. Souring of milk Select the correct answer using the code given below.

Souring of milk is a chemical change because it involves a chemical reaction where bacteria convert lactose into lactic acid, resulting in the formation of a new substance with different properties. Crystallization of sodium chloride is a physical change, not chemical, as it merely involves the transition of salt from a dissolved state to a solid crystal without altering its chemical identity. The core concept tested is the distinction between physical changes (reversible, no new substance formed) and chemical changes (irreversible, new substance formed).