Iron sheet kept in moist air gets covered with rust. Rust is

Rust is a chemical compound formed when iron reacts with oxygen and moisture in the air. This process, known as rusting, involves a chemical change where a new substance is created [2]. Chemically, rust is identified as hydrated iron (III) oxide, with the general formula Fe2O3·nH2O. Unlike a mixture, where components retain their individual properties and can be separated by physical means, rust is a distinct chemical entity with a fixed composition of iron and oxygen atoms bonded together. The reaction requires both oxygen and water to proceed, leading to the formation of this reddish-brown flaky substance [2]. Since it is a new substance formed through a chemical reaction between elements, it is classified as a compound rather than an element or a simple mixture [3].

Sources

1. [1] Science-Class VII . NCERT(Revised ed 2025) > Chapter 5: Changes Around Us: Physical and Chemical > 5.3.1 Rusting > p. 62
2. [2] Science , class X (NCERT 2025 ed.) > Chapter 3: Metals and Non-metals > 3.5 CORROSION > p. 53
3. [3] Science ,Class VIII . NCERT(Revised ed 2025) > Chapter 8: Nature of Matter: Elements, Compounds, and Mixtures > Snapshots > p. 131