Question

Classify the following as physical or chemical change.

Making cheese from milk.

Answer 1

Making cheese from milk is a chemical change.

A chemical change is a permanent change in which new substances are formed whose chemical and physical properties are completely different from that those of the original substance.

Characteristics of chemical change:

• Change is permanent and cannot be reversed.
• One or more new substance is formed.
• Composition of the original substance does not remain the same.
• The heat or light may be produced or consumed during the reaction.
• Exchange of energy takes place during the reaction.

Thus, when cheese is prepared from milk the composition of milk and cheese is entirely different and the change is irreversible i.e. once the cheese is formed it cannot be transformed back to milk. Thus it is a chemical change.