Characteristics Of an Explosion

X Not like a fire – does not need oxygen Energy and gases released as products of rxn Expanding gases produce a pressure wave (= longitudinal wave) X

Compressions = where coils are close together Rarefactions = where coils are far apart Wave transfers energy from one end to other Explosion energy forces particles in air to move back and forth If in container, stretches until bursts sending flying debris ( = shrapnel) all over

Explosives = chemicals that react under certain conditions to cause explosions Most are solids 2 categories – based on rate of reaction 1. low – slower, can burn rather than explode 2. high – faster, violent

Low Explosives Burn rapidly, but explode only when confined Produce combustion rxn = deflagration = rapid, intense burning - produces pressure wave w/ a speed of less than 340 m/s (speed of sound) Used as propellants - produces enough gas and energy to push objects away from original explosion

Need a small amount of energy to ignite low explosive Examples: Black powder used to make safety fuses – carries spark to another explosive Smokeless gunpowder – safest and most powerful

Fireworks = black powder or smokeless gunpowder and a fuse - rxn produces gases putting pressure on paper surrounding firework -> explosion - elements added to firework give off the colors

Natural gas – when mixes w/ oxygen can explode if ignited - smell added to it to detect it

High Explosives Materials that detonate = results in violent disruption to the surrounding area Do not need to be confined to explode Many decompose upon detonation Example – TNT (C7H5N3O6) 2 C7H5N3O6  3N2 + 5H2O + 7CO + 7C (Carbon will leave black soot)

Detonate easily producing pressure wave that moves as fast as 8,500 m/s = shock wave Widespread damage Used to blast or shatter a target 2 categories – primary and secondary

Primary – dangerous - sensitive to heat, pressure, and movement - used to detonate other explosives or in shotgun shells Examples – lead styphnate, mercury fulminate, nitroglycerin

Secondary – relatively safe - not as sensitive, but can cause very violent explosions - used for military or commercial purposes Examples – TNT and dynamite (= nitroglycerin and silica mixture)

Categories based on usage 1. commercial – mining, road construction, demolition 2. military – ex. RDX (form of C-4), PETN, TNT 3. improvised explosive – illegal; low explosives in a container - used for terrorism & guerrilla warfare