Question

Classify the following change as physical or chemical:

Conversion of milk into curd.

Answer 1

Chemical change:

• A chemical change is a permanent change in which new substances are formed.
• The chemical change is permanent and cannot be reversed by a simple physical method.
• A chemical change involves an exchange of energy in the form of heat or light.
• For example, rusting of iron, burning of wood, respiration, conversion of milk into curd, etc.
• When the curd is formed from the milk, its properties are different from that of milk.
• It is not possible to obtain milk from curd, so the change is irreversible.

Therefore, the formation of curd from milk is a chemical change.