Of an Explosion

CHARACTERISTICS

• 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