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.

1. 1 and 2 only
2. 3 only
3. 1, 2 and 3
4. None

Explanation

Option (b) is correct

• Crystallization of sodium chloride: This is a physical change, as the process involves the transition of sodium chloride from its dissolved state to a solid crystalline form without altering its chemical composition.
• Melting of ice: This is also a physical change, as it involves the transformation of water from solid to liquid form, with no change in its chemical structure (H₂O remains the same).
• Souring of milk: This is a chemical change because the process involves the breakdown of lactose (a sugar) into lactic acid by bacteria, resulting in a new substance with different properties.

Answer: (b) 3 only; Difficulty Level: Easy