The scenario that demonstrates a chemical change is:
Iron (Fe) reacting to water (H2O) and oxygen (O) to form iron oxide (Fe2O3).
In this reaction, the iron undergoes a chemical change as it reacts with water and oxygen to form a new substance (iron oxide).
The other options involve physical changes:
- Steam condensing on a mirror is a physical change as it involves a phase change from gas to liquid.
- Sugar and water mixing to create sugar water is a physical change, because the sugar dissolves in water but does not change its chemical structure.
- Dry ice vaporizing is also a physical change, as it involves a phase change from solid to gas.
Therefore, the only option that involves a chemical change is the formation of iron oxide.