See Also: Atomic Bomb, Hydrogen Bomb, Nuclear Energy
A substance that undergoes rapid decomposition or combustion, evolving much Heat and producing a large volume of Gas (see States Of Matter). The heat evolved causes the gas to expand greatly, exerting the enormous Pressure of explosions. Important explosives include TNT (trinitrotoluene), dynamite,
and nitroglycerin. Chemical explosives are of two general kinds. Some, e.g.,
gunpowder, are mixtures of readily combustible but not necessarily explosive
substances, which, when set off (by ignition), undergo very rapid combustion.
Others, called high explosives (e.g., TNT), are compounds whose Molecules are unstable and can undergo explosive decomposition (detonation) without
burning. The latter kind is used in warfare (e.g., in bombs, explosive shells,
torpedoes, and missile warheads) and for blasting rock in mining and construction
work. Nondetonating explosives, e.g., gunpowder and modern smokeless powders,
are used as propellants for bullets and in fireworks. Nuclear explosives
release Energy by transformation of the atomic nucleus.