Introduction:
The rusting of iron is a chemical change. It is a common process that occurs when iron is exposed to moisture and oxygen in the air. This chemical reaction leads to the formation of rust, which is a reddish-brown compound known as iron oxide.

Explanation:
Chemical change:
Rusting of iron is a chemical change because it involves a chemical reaction that results in the formation of a new compound. When iron reacts with moisture and oxygen, it undergoes oxidation, which leads to the formation of iron oxide. This change is irreversible, meaning that the iron cannot be restored to its original form without the use of external processes such as cleaning or sanding.

Formation of iron oxide:
When iron comes into contact with moisture and oxygen, a series of chemical reactions occur. Firstly, the iron reacts with oxygen in the air to form iron(II) oxide (FeO). This is further oxidized in the presence of moisture to form hydrated iron(III) oxide, commonly known as rust (Fe2O3•xH2O). The process of rusting involves the transfer of electrons from the iron atoms to the oxygen atoms, resulting in the formation of iron oxide.

Characteristics of rust:
Rust is a brittle and flaky substance that adheres to the surface of iron or steel. It has a reddish-brown color, which is why it is easily distinguishable. Rust also has a higher volume than iron, which can cause the iron to expand and weaken over time. This can lead to the degradation of iron structures and objects.

Prevention of rusting:
Rusting can be prevented or slowed down through various methods such as applying a protective coating, such as paint or oil, to the iron surface. This creates a barrier that prevents moisture and oxygen from coming into contact with the iron. Another method is to use corrosion-resistant materials, such as stainless steel, which contain elements that resist oxidation.

Conclusion:
In conclusion, the rusting of iron is a chemical change that involves the formation of iron oxide. It is a natural process that occurs when iron is exposed to moisture and oxygen. Understanding the chemical nature of rusting allows us to develop methods to prevent or slow down this process, ensuring the longevity and durability of iron structures and objects.

Rusting of iron is a chemical change...so C is correct