Rusting is a slow chemical change that occurs due to oxidation of iron or iron objects. It takes place in the presence of air and moisture. Due to rusting, flaky brown rust is formed on iron objects. It is a red-orange coloured iron oxide which is formed by the oxidation of iron in presence of oxygen and moisture or water.

Substances that take part in a chemical reaction and react with each other to give the desired products at the end of the reaction are known as reactants. Reactants undergo a chemical change in which chemical bonds are broken, and new bonds are formed to make products. In a chemical equation, reactants are listed on the left side of the arrow, while products are on the right side. For example, in the chemical reaction: 2 Mg + O 2 → 2 MgO . Mg , O 2 are reactants.

The species that are formed from chemical reactions are known as products. During a chemical reaction, reactants are transformed into products after passing through a high energy transition state. New bonds are formed after breaking old bonds in the reactants to form the products. For example, in the chemical reaction: 2 H 2 + O 2 → 2 H 2 O , the product is H 2 O .