The Chemistry Behind Fireworks
By Darryl Ho 4L04
What is a firework ? What are fireworks made of ? The chemistry behind fireworks Stage 1 : Redox Reaction Stage 2 : Excitement of electrons Effect : Different metals, Different colours
Content
What is a Firework ?
It is a low explosive pyrotechnic device used primarily for special effects and entertainment
purposes.
Oxidising Agent Firework Rocket Fuel Gunpowder Colouring Agent Binder
What is a Firework Made Of ?
Stage I
Lift Off
STAGE I - The Lift Off
Redox reactionRedox reactionbetween the oxidising between the oxidising agents and the rocket fuelagents and the rocket fuel
Thermal decomposition of oxidising agents Oxidising Agents used: KNO3, KClO4, KClO3
Potassium nitrate is reduced into potassium oxide and nitrogen gas as it loses oxygen.
Thus reduction of potassium nitrate takes place and oxygen gas is produced.
STAGE I - Redox Reaction
4 KNO3 4 K2O + 2N2 + 5 O 2
Oxidation of rocket fuel Rocket Fuel: Carbon + Sulphur Powder Sulphur and carbon reacts with the oxygen provided by
the reduction of oxidising agents to form sulphur dioxide and carbon dioxide respectively
Both sulphur and carbon are oxidised to gain oxygen, forming large amounts of sulphur dioxide and carbon dioxide as products.
STAGE I - Redox Reaction
O (g) + S(s) S O (g) 2
O (g) + C(s) C O (g) 2
2
2
Large volumes of carbon dioxide and sulfur dioxide gases are formed.
They exert a force on the ground due to high pressure in the rocket, creating
an upward thrust on the rocket.
This lifts the rocket into the air.
The Result
STAGE II – Excitement of Electrons
Excitement of electrons of metal atoms
STAGE II - Heating of Colouring Agents
Coloring agents used are salts of metals or their compounds.
The metal atoms or cations absorb the thermal energy produced by the combustion of sulfur and carbon powder.
The thermal energy that is absorbed causes the electrons of the atom from the lowest energy state to become excited and enter the highest energy state of an atom, called an excited state.
The excess energy of the excited state is released as the electrons descend to lower energy states.
The energy released is emitted as light energy in the process.
STAGE II - Heating of Colouring Agents
The End Result
Effect - Different Metals ………. Different Colours The electrons of different metals release different
amount of energy when excited and produce an electromagnetic wave of a particular wavelength.
Hence, different metals produce different colors of light when burnt.
Higher Energy
Lower Energy
Shorter Wavelengths
Higher Wavelengths
Effect - Different Metals ……….Different Colours
COLOUR CHEMICAL WAVELENGTH
Red Lithium Salts 650 nm
Orange Calcium Salts Calcium (II) Chloride
670 nm
Yellow Sodium Salts Sodium Chloride
610 nm
Blue Copper(I) Chloride 535 nm
Silver Magnesium, Aluminium
and Titanium Salts
The End. Thank You.