Is there a chemical or physical change when bicycle rusts in the rain?

Explanation:

- Rusting is the process in which iron metal reacts with oxygen and water to form iron oxide. This process is also called oxidation. Rusting is a chemical change because a new substance, iron oxide, is formed.

- The chemical formula for the reaction between iron, oxygen, and water is:

$$4Fe_{(s)}+3O_{2(g)}+6H_2O_{(l)}\rightarrow 4Fe(OH)_{3\cdot}xH_2O_{(s)}$$

where \(x\) can vary between 0 and 4.

Physical changes occur when the form of a substance changes without altering its chemical composition. Some examples of physical changes include melting, freezing, and bending. In contrast, chemical changes occur when the chemical composition of a substance is altered, resulting in the formation of new substances.