What type of energy is considered to be released during combustion reactions?

During combustion reactions, chemical energy is released as the reactants (typically fuels) undergo a chemical transformation when they react with an oxidizer (usually oxygen). This process breaks the molecular bonds in the fuel and the oxidizer, rearranging them into new products, often in the form of gases, heat, and light. The energy that is stored in the chemical bonds of the fuel is released as heat and light, which is a characteristic manifestation of combustion.

While thermal energy can also be considered a result of combustion since it is the heat energy that is produced and often measured, the initial energy that fuels the reaction and is converted into thermal energy is primarily the chemical energy stored in the fuel itself. Thus, chemical energy is the correct answer, as it specifically refers to the form of energy that is transformed and liberated during the combustion process.