| Nuclear fission | U-235 splits into smaller nuclei + energy | Very large amount of energy released |
| Neutralisation | Acid + Base → Salt + Water + heat | Rise in temperature |
| Rusting of iron | Iron + oxygen + water → rust + heat | Heat released slowly |
| Combustion of methane | CH₄ + O₂ → CO₂ + H₂O + energy | Produces heat and light |
| Thermite reaction | Iron oxide + aluminium → iron + aluminium oxide + energy | Molten iron formed |
| Respiration | Glucose + oxygen → carbon dioxide + water + energy | Produces body heat |
| Slaking of lime (quicklime + water) | CaO + H₂O → Ca(OH)₂ + heat | Mixture becomes hot |