Question

1. Souring of milk is a __________ change.

Answer 1

• A chemical change occurs when there is a change in the chemical properties of the substance and a new substance is formed.
• Souring of milk is a chemical change because the bacteria Lactobacillus which is present in milk converts the lactose sugar into energy and lactic acid is formed which is sour in taste.
• Thus, a new substance lactic acid is formed.

Hence, souring of milk is a chemical change.