Here's why:

* Chemical weathering involves changes in the chemical composition of rocks. This happens when minerals in the rocks react with substances in the environment, like water, oxygen, or acids.

* Oxidation is a specific type of chemical weathering where oxygen reacts with minerals in the rock. This often results in the formation of oxides, which are weaker and more easily broken down than the original minerals.

For example, iron in rocks can oxidize to form rust (iron oxide). Rust is weaker than the original iron mineral and crumbles easily, contributing to the breakdown of the rock.