Which of the following is/are the example/ examples of chemical change?1. Crystallisation of sodium chloride2. Melting of ice3. Souring of milkSelect the correct answer using the code given below.
✓ Correct answer: b) 3 only
ExplanationChemical Change involves the transformation of one material into another, the creation of new materials with unique properties, and the creation of one or more new substances.Option 1 is incorrect: Crystallization is a physical process where a dissolved substance transitions from a liquid solution to a solid crystalline form.In the case of sodium chloride (table salt), when a saturated salt solution evaporates, salt crystals form.This process does not alter the chemical composition of sodium chloride.Option 2 is incorrect: Melting is the phase transition of a substance from solid to liquid.When ice (solid water) melts, it becomes liquid water.This change is purely physical, as the molecular structure of H₂O remains unchanged during the process.UPSC GS Paper-I PYQs 576 Option 3 is correct: Souring of milk is a chemical change resulting from the fermentation process.Bacteria in the milk convert lactose (milk sugar) into lactic acid, leading to a decrease in pH and the characteristic sour taste.This transformation alters the chemical composition of the milk, producing new subst
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