<P> In addition to stellar nuclear explosions, a man - made nuclear weapon is a type of explosive weapon that derives its destructive force from nuclear fission or from a combination of fission and fusion . As a result, even a nuclear weapon with a small yield is significantly more powerful than the largest conventional explosives available, with a single weapon capable of completely destroying an entire city . </P> <P> Explosive force is released in a direction perpendicular to the surface of the explosive . If a grenade is in mid air during the explosion and the direction of the blast will be 360 ° . In contrast, in a shaped charge the explosive forces are focused to produce a greater local effect . </P> <P> The speed of the reaction is what distinguishes an explosive reaction from an ordinary combustion reaction . Unless the reaction occurs very rapidly, the thermally expanding gases will be moderately dissipated in the medium, with no large differential in pressure and there will be no explosion . Consider a wood fire . As the fire burns, there certainly is the evolution of heat and the formation of gases, but neither is liberated rapidly enough to build up a sudden substantial pressure differential and then cause an explosion . This can be likened to the difference between the energy discharge of a battery, which is slow, and that of a flash capacitor like that in a camera flash, which releases its energy all at once . </P> <P> The generation of heat in large quantities accompanies most explosive chemical reactions . The exceptions are called entropic explosives and include organic peroxides such as acetone peroxide It is the rapid liberation of heat that causes the gaseous products of most explosive reactions to expand and generate high pressures . This rapid generation of high pressures of the released gas constitutes the explosion . The liberation of heat with insufficient rapidity will not cause an explosion . For example, although a unit mass of coal yields five times as much heat as a unit mass of nitroglycerin, the coal cannot be used as an explosive (except in the form of coal dust) because the rate at which it yields this heat is quite slow . In fact, a substance which burns less rapidly (i.e. slow combustion) may actually evolve more total heat than an explosive which detonates rapidly (i.e. fast combustion). In the former, slow combustion converts more of the internal energy (i.e. chemical potential) of the burning substance into heat released to the surroundings, while in the latter, fast combustion (i.e. detonation) instead converts more internal energy into work on the surroundings (i.e. less internal energy converted into heat); c.f. heat and work (thermodynamics) are equivalent forms of energy . See Heat of Combustion for a more thorough treatment of this topic . </P>

What is the difference between combustion and explosion