Chemical oxidation is a process where a substance loses electrons, often resulting in an increase in its oxidation state. This reaction typically involves the addition of oxygen or the removal of hydrogen. Oxidation is a key part of many chemical reactions, including combustion and respiration, where energy is released. In many cases, oxidation occurs alongside a reduction reaction, where another substance gains the electrons lost. Together, these reactions are known as redox reactions. Common examples of oxidation include the rusting of iron and the browning of apples when exposed to air.