Burning fuels such as hydrocarbons is useful because it releases light and heat energy. During combustion, the chemical bonds in hydrocarbons break and react with oxygen to form carbon dioxide and water. This reaction releases significant amounts of thermal energy (heat) and also produces light due to the exothermic nature of the reaction. The energy released is primarily chemical potential energy stored in the bonds of the hydrocarbon molecules, which transforms into thermal energy and light energy when burned. This makes combustion a highly effective way to convert chemical energy into useful heat and light for powering engines, heating homes, and generating electricity.