Combustion of fuels such as wood, coal and oil petroleum Thermite reaction Reaction of alkali metals and other highly electropositive metals with water Condensation of rain from water vapor Mixing water and strong acids or strong bases Mixing acids and bases Dehydration of carbohydrates by sulfuric acid The setting of cement and concrete Some polymerisation reactions such as the setting of epoxy resin Reaction of most metals with halogens or oxygen Nuclear fusion in hydrogen bombs and in stellar cores (to iron) Nuclear fission of heavy elements