Question

What physical observation can confirm that iron has rusted?

Answer 1

Rusting

1. When Iron is exposed to moisture or Oxygen, its oxidation occurs and it is called as Rusting of iron.
2. Rusting of Iron is a Chemical change because a new substance Iron oxide (${\mathrm{Fe}}_2{\mathrm{O}}_3$) is formed.
3. During this chemical reaction, Iron ($\mathrm{Fe}$) is converted into Iron oxide/Ferric oxide (${\mathrm{Fe}}_2{\mathrm{O}}_3$). $$\begin{gathered} 4\mathrm{Fe}\left(\mathrm{s}\right)+3{\mathrm{O}}_2\left(\mathrm{g}\right)+2.{\mathrm{xH}}_2\mathrm{O}\left(\mathrm{l}\right)\to 2{\mathrm{Fe}}_2{\mathrm{O}}_3.{\mathrm{xH}}_2\mathrm{O}\left(\mathrm{aq}\right) \\ \left(\mathrm{Iron}\right)\left(\mathrm{Oxygen}\right)\left(\mathrm{Water}\right)(\mathrm{Hydrated}\mathrm{ferric}\mathrm{oxide}) \end{gathered}$$
4. The Rust usually appears as a red, brown or orange flaking or pitting of the metal surface.

Therefore, the rusted Iron can be observed as a red, brown or orange flaking or pitting of the metal surface.