Rusting of iron is a chemical change because:

• A. It is temporary
• B. It can be cleaned and the original substance recovered
• C. It is a slow reaction
• D. A new substance is formed

Rusting of iron is classified as a chemical change primarily because:

Formation of a New Substance

During rusting, iron reacts with oxygen and moisture in the environment, resulting in the formation of iron oxide, commonly known as rust. This process creates a substance that is different from the original iron.

Why Other Options Are Incorrect

• Temporary Nature: Rusting is not temporary; it can lead to significant deterioration over time.
• Recovering Original Substance: Once iron has rusted, it cannot be cleaned to recover the original iron without significant effort.
• Reaction Speed: While rusting is a slow process, the speed of the reaction does not determine whether it is a chemical change.

In summary, the correct answer is D: A new substance is formed, which is the key indicator of a chemical change.