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.
A
1 and 2 only
B
3 only
Correct Answer
C
1, 2 and 3
D
None
Explanation
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).
ChemistryChemical vs. Physical ChangesChemical changephysical changecrystallization of sodium chloridemelting of icesouring of milknew substance formationreversible change