Thermal energy.

Thermal, kinetic, nuclear, and chemical energy are all availab­le for human work. People obtain them from fuel, solar radiation, moving water, geothermal facilities or nuclear fission.

Today, however, most energy comes from burning fuels. Burning releases the chemical energy stored in the bonds between atoms and molecules of the fuels. The thermal energy released from the fuels burning is the result of a chemical reaction called oxidation. Oxi­dation is the chemical combination of oxygen with another element. The elements such as carbon, sulphur and nitrogen combined with oxy­gen to produce such oxides as carbon dioxide and nitrogen oxide, releasing thermal energy in the process. This is the reason fuels such as wood and coal lose so much mass in the burning process. Oxidation releases the energy in stored chemical bonds.

Valuable as oxidation is in providing energy for human work; its by-products affect the atmosphere, climate and the health of liv­ing organisms. Carton monoxide, sulphur dioxide and nitrogen oxi­de are all injurious to human health; oxides or sulphur and nitro­gen become acids that living and nonliving matter; and car­bon dioxide, a greenhouse gas, is instrumental in global warming. The destructive effects of oxidation, together with dwindling supp­lies of fossil fuels provide the impetus for development of al­ternative sources.