Final answer:
Chemical reactions that always involve oxidation are single replacement and combustion reactions.
Step-by-step explanation:
In chemistry, the types of chemical reactions that always involve oxidation are single replacement and combustion reactions.
In a single replacement reaction, an element replaces a part of a compound, resulting in a change in oxidation number for the elements involved.
In a combustion reaction, a substance combines with oxygen, resulting in the oxidation of the substance being burned.