Explain the following in terms of gain or loss of oxygen with two examples each.

(a) Oxidation is a chemical process in which a substance gains oxygen atoms, or in which the number of atoms of another element in a compound decreases as the result of a reaction. Here are a few examples of oxidation:

The rusting of iron: When iron is exposed to oxygen and moisture, it reacts with the oxygen to form iron oxide (also known as rust). This is an example of oxidation, as the iron gains oxygen atoms during the reaction.

The combustion of propane: When propane is burned, it reacts with oxygen to produce carbon dioxide and water. This is an example of oxidation, as the propane is gaining oxygen atoms during the reaction.

(b) Reduction is a chemical process in which a substance loses oxygen atoms, or in which the number of atoms of another element in a compound increases as the result of a reaction. Here are a few examples of reduction:

The reduction of copper oxide: When copper oxide is heated in the presence of hydrogen gas, it reacts to form copper and water. This is an example of reduction, as the copper oxide is losing oxygen atoms during the reaction.

The reduction of nitrate ions: When nitrate ions (NO3-) are reduced, they are converted to nitrite ions (NO2-). This is an example of reduction, as the nitrate ions are losing oxygen atoms during the reaction.