A firework is an incendiary device or material that can be used forsignalling orentertainment. There are chemicals located in the nose ofthe rocket that explode, producing the colours seen.
The art of fireworks, first originated in ancient China, with thefirst explosive being made from a mixture of black powder during theSung dynasty. It is believed that the explosive mixture was created bya combination of sulfur, saltpeter and charcoal. The Chinese foundthat the combination of these ingredients was extremely flammable andwould explode if set alight.
Fireworks were originally created for the purpose of entertainment andtoday they are still widely used in celebration to mark specialoccasions. The thrill and excitement generated by fireworks,brightening the night sky and immersing it with vivid displays ofcolour and technicality, which makes them a crowd pleaser.
Behind all the excitement of fireworks, chemistry plays an importantrole in creating the vivid colours we witness lighting up the sky. Theactual chemical reactions that take place in the explosions requirethe use of oxidisers, reducing agents and binders. The additions ofvarying metal chlorides add the colours.
(See Table 1)OxidisersAn oxidizing agent producing the oxygen required to burn the mixtureReducersAn agent e.g. Sulphur, that burn the oxygen and produce hot gasesBindersRequired to hold the mixture in a lumpTABLE 1: Oxidisers, Reducers and BindersThe ability of producing coloured light from the principles offireworks have allowed this technology to be applied for bothindustrial and military uses. Fireworks are now used for flares andsmokescreens in modern society.
In Australia the non-authorised use of fireworks are banned due to thepossibility of death or injury caused by stray rockets anduncontrollable explosions. Care is also needed because fireworks candamage your hearing and the fumes produced are toxic.
Chemical Background:The production of light in fireworks, rely on basic chemicalprinciples such as redox reactions, combustion and the excitement ofelectrons in metal ions when heated.
Redox reactions are chemical reactions in which both oxidation andreduction take place. Oxidation is a process where oxygen is gained,or hydrogen lost and reduction is where oxygen is lost and hydrogen isgained. In order for the reactions to take place in a firework,oxidizers such as nitrates produce the oxygen to burn and reducerssuch as sulphur reduce the oxygen into hot gases. (Scheme 1)NO3 (s) + S (s) ÞNO (g) + SO2 (g)Scheme 1With any explosive device, combustion occurs. Combustion is a processof rapid oxidation of a substance with simultaneous release of heatand sometimes light. This is important in fireworks because of theredox reactions that occur. During combustion of fireworks someundesirable gases can be produced such as sulphur dioxide, whichcontributes to acid rain and air pollution. (Scheme 2)S (s) + O2 (g) ÞSO2 (g)Scheme 2Fireworks require chemical reactions to create the vivid colours thatare emitted. However there are three essential chemical items neededto allow the reactions to occur. They are an oxidizer, to produceoxygen needed to let the firework burn, reducing agents to burn theoxygen emitted to produce hot gases which glow (Heat causes asubstance to become hot and glow) and binders that hold the mixtureinto a lump.
Oxidisers---------The common oxidisers are nitrates, chlorates or perchlorates. They arenecessary because they produce the oxygen to burn the mixture.
Nitrates are composed of a metal ion and a nitrate ion and in areaction release one third of their oxygen. (Scheme 3)2NaNO3 (s) Þ2NaNO2 (s) + 3O2 (g)Scheme 3Chlorates are composed of a metal ion and a chlorate ion and releaseall of their oxygen, causing a more speedy reaction. Chlorates are anexample of complete combustion in which all the oxygen is burnt andthe maximum quantity of heat energy is released. This results in avery explosive chemical reaction and...
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