* Chemical properties describe how a substance reacts with other substances. The rusting process involves a chemical reaction between iron, oxygen, and sometimes water. This results in a new substance (rust) with different properties than the original iron.
* Physical properties can be observed without changing the substance's composition. Examples include color, density, melting point, etc. These properties don't involve chemical reactions.
In summary: The tendency of iron to rust is a chemical property because it describes how iron behaves in a chemical reaction, changing its composition and forming a new substance.
