Final answer:
The formation of rust on metal is a chemical change because it involves new chemical bonds forming between iron and oxygen, resulting in the new substance, iron oxide or rust.
Step-by-step explanation:
Is rust forming on metal a chemical or physical change? The formation of rust on metal is a chemical change. Rust is iron oxide, a different kind of matter than the iron, oxygen, and water present before the rust formed. The reaction that takes place is Fe + O₂ → Fe₂O₃, indicating that new chemical bonds have been formed, leading to the creation of a new substance. Color change is a common indicator of a chemical change, and in the case of rust formation, we observe the metal transitioning from its original color to an orange or red flaky substance. This transformation is due to the chemical reaction of iron with oxygen, commonly referred to as corrosion. Rusting is an expensive problem, causing significant financial impact due to the damage it causes to metal structures and items.