The Chemistry of Fireworks.

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A firework is an incendiary device or material that can be used for signalling orentertainment. There are chemicals located in the nose of the rocket that explode, producing the colours seen.

The art of fireworks, first originated in ancient China, with the first explosive being made from a mixture of black powder during the Sung dynasty. It is believed that the explosive mixture was created by a combination of sulfur, saltpeter and charcoal. The Chinese found that the combination of these ingredients was extremely flammable and would explode if set alight.

Fireworks were originally created for the purpose of entertainment and today they are still widely used in celebration to mark special occasions. The thrill and excitement generated by fireworks, brightening the night sky and immersing it with vivid displays of colour and technicality, which makes them a crowd pleaser.

Behind all the excitement of fireworks, chemistry plays an important role in creating the vivid colours we witness lighting up the sky. The actual chemical reactions that take place in the explosions require the use of oxidisers, reducing agents and binders. The additions of varying metal chlorides add the colours.
(See Table 1)

TABLE 1: Oxidisers, Reducers and Binders

The ability of producing coloured light from the principles of fireworks have allowed this technology to be applied for both industrial and military uses. Fireworks are now used for flares and smokescreens in modern society.

In Australia the non-authorised use of fireworks are banned due to the possibility of death or injury caused by stray rockets and uncontrollable explosions. Care is also needed because fireworks can damage your hearing and the fumes produced are toxic.

Chemical Background:

The production of light in fireworks, rely on basic chemical principles such as redox reactions, combustion and the excitement of electrons in metal ions when heated.

Redox reactions are chemical reactions in which both oxidation and reduction take place. Oxidation is a process where oxygen is gained, or hydrogen lost and reduction is where oxygen is lost and hydrogen is gained. In order for the reactions to take place in a firework, oxidizers such as nitrates produce the oxygen to burn and reducers such as sulphur reduce the oxygen into hot gases. (Scheme 1)

NO3 (s) + S (s) ޼/strong>NO (g) + SO2 (g)

Scheme 1

With any explosive device, combustion occurs. Combustion is a process of rapid oxidation of a substance with simultaneous release of heat and sometimes light. This is important in fireworks because of the redox reactions that occur. During combustion of fireworks some undesirable gases can be produced such as sulphur dioxide, which contributes to acid rain and air pollution. (Scheme 2)

S (s) + O2 (g) ޼/strong>SO2 (g)
Scheme 2

Fireworks require chemical reactions to create the vivid colours that are emitted. However there are three essential chemical items needed to allow the reactions to occur. They are an oxidizer, to produce oxygen needed to let the firework burn, reducing agents to burn the oxygen emitted to produce hot gases which glow (Heat causes a substance to become hot and glow) and binders that hold the mixture into a lump.


The common oxidisers are nitrates, chlorates or perchlorates. They are necessary because they produce the oxygen to burn the mixture. Nitrates are composed of a metal ion and a nitrate ion and in a reaction release one third of their oxygen. (Scheme 3)

2NaNO3 (s) ޼/strong>2NaNO2 (s) + 3O2 (g)

Scheme 3

Chlorates are composed of a metal ion and a chlorate ion and release all of their oxygen, causing a more speedy reaction. Chlorates are an example of complete combustion in which all the oxygen is burnt and the maximum quantity of heat energy is released. This results in a very explosive chemical reaction and caution is required. (Scheme 4)

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KClO4 (s) ޼/strong>KCl (s) + 2O2 (g)

Scheme 4

Reducing Agents

Reducing agents work by burning the oxygen that the oxidisers release, producing hot gases. Two common reducing agents are sulphur and charcoal. The two of these react with oxygen to form sulphur dioxide and carbon dioxide respectively. (Scheme 5)

S (s) + O2 (g) ޼/strong>SO2 (g)

C (s) + O2 (g) ޼/strong>CO2 (g)

Scheme 5

Normally pyrotechnics will combine both of these reducers together resulting in a slower reaction. Therefore reducing agents are used to control the speed of reaction. To speed the reaction, metals are often added, ...

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