How is energy from chemical energy released and transferred into thermal energy?

Answer 1

Chemical compounds, like oil or coal, hold potential chemical energy in the powerful molecular bonds with the compound. If such a chemical compound undergoes a chemical reaction (in this case in an internal combustion engine), the potential chemical energy will be released in the form of thermal energy. Of course, no energy transformation is 100% efficient as some of the potential chemical energy is either not converted at all or converted into a different form of energy. Take the example of a fire in one's fire place. Although a large percentage of the potential chemical energy in the wood is converted into thermal energy that we can feel as heat, some of the energy is converted into light, that we can see as the brightness of the fire, and some is converted into sounds, as we can hear in the roaring of the fire.