Beauty of Chemistry - Fireworks
At 9 pm tonight, a 23-minute firework display was held for 2015 National day. The sky was filled with colors.
But, as a chemist, what do you think about all these?
Do you know how it exactly works?
Fireworks = Fuel + Oxidising agent + reducing agent + coloring agent
One typical reaction (overall)
6 KNO3 + C7H4O + 2 S → K2CO3 + K2SO4 + K2S + 4 CO2 + 2 CO + 2 H2O + 3 N2
Fuel (Charcoal C7H4O) It loses electrons to OA and release massive amount of energy.
Oxidising Agents (nitrates NO3-, chlorates ClO3- or perchlorates ClO4-)
It is to produce oxygen for fuel to burn.
Reducing Agents (Sulphur/charcoal)
It burns the oxygen provided by the oxidising agents to produce hot gasses.
Colouring Agents (Metal ions)
In flame test, we know that different metal ions can give different colors. And here are some common colors used in fireworks.
Strontium
Copper
Barium
Sodium
Calcium
Magnesium
By combining different metals in specific proportions, we can get more colors.
E.g. Strontium + Copper --> Purple
As the reaction goes, hot gases are produced. These atoms collide with each other frequently in the explosion. As a result, electrons are pushed to higher energy level, and shortly, it returns to ground state to release energy in the forms of light.
Do you know how to illustrate this using the Bohr model?
Also, it is hard to produce blue-colored firework.
(light with short wavelength)
Do you know how to describe with the blackbody radiation curve?
The following video explains more on fireworks: