Question

A new iron bar is lustrous while one kept out for long time is not. Why so?

Answer 1

A new iron bar is lustrous while one kept out for a long time is not because lustre is one of the properties of metals. But, it loses it by time because it reacts with the oxygen and water vapour present in air and forms iron rust.

The chemical reaction representing it is:

4Fe + $3O_{2}$ + x$H_{2} O$ ⇒ $2Fe_{2}O_{3}.xH_{2}O$

But even an old piece iron could be made lustrous after it is freshly cut.

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