The example that demonstrates a chemical change is:
Iron (Fe) reacting to water (H2O) and oxygen (O) to form iron oxide (Fe2O3).
This process involves a chemical reaction where iron reacts with water and oxygen to create a new substance, iron oxide, which is a sign of a chemical change.
The other options involve physical changes (like vaporizing or condensing) or a mixture (sugar and water) that do not result in the formation of a new substance.