What is an example of a chemical change?

A chemical change involves a process where the molecular structure of a substance is altered, resulting in the formation of one or more new substances with different properties. The rusting of iron exemplifies a chemical change because it involves the reaction of iron with oxygen and moisture in the environment, leading to the formation of iron oxide (rust). This alteration in composition indicates a chemical transformation, as the original materials cannot be easily reverted to their original state.

In contrast, boiling water and melting chocolate are physical changes; they involve changes in state or form without altering the molecular structure of the substance. Chopping vegetables also represents a physical change, as the chemical composition of the vegetables remains unchanged despite their physical alteration in size or shape. These processes do not produce new substances, making rusting of iron a clear example of a chemical change.