Which of the following does NOT represent a physical change?

Rusting iron does not represent a physical change because it involves a chemical reaction. During rusting, iron combines with oxygen in the presence of moisture to form iron oxide, commonly known as rust. This process alters the chemical composition of the iron, creating a new substance with different properties. In contrast, the other choices—melting ice, boiling water, and chopping wood—are all examples of physical changes. Melting ice is the change of state from solid to liquid, boiling water is the transition from liquid to gas, and chopping wood changes the size and shape of the wood without affecting its chemical identity. These processes do not result in the formation of new substances, which is why they are classified as physical changes.