Which of the following is NOT an example of a physical change?

The rusting of iron is a chemical change, not a physical change. A physical change involves a transformation in the state or appearance of a substance, without altering its chemical composition. In the case of rusting, iron reacts with oxygen and moisture in the environment to form iron oxide, which is a completely different substance with new chemical properties. This process cannot be easily reversed by physical means.

On the other hand, boiling water, melting ice, and freezing juice are all physical changes. In these examples, the substances undergo a change in state – from liquid to gas in boiling, from solid to liquid in melting, and from liquid to solid in freezing – but maintain their original chemical composition throughout these processes. Therefore, identifying rusting as an example of a chemical change highlights the distinction between physical and chemical changes effectively.