Briefly state why the combustion of methane in oxygen is exothermic?

The combustion of methane in oxygen is exothermic because it releases energy in the form of heat and light as the chemical bonds in the reactants are broken and new bonds are formed in the products. This release of energy results in a decrease in the overall energy of the system, making the reaction exothermic.

The combustion of methane in oxygen is exothermic because the bonds formed in the products (CO2 and H2O) are stronger than the bonds broken in the reactants (CH4 and O2). The energy released by the formation of these stronger bonds is greater than the energy required to break the weaker bonds, resulting in a net release of energy as heat.