Fireworks are definitely a work of art to look at. However, in reality, they are a work of science and chemistry. Here is the explanation of the chemistry behind them.
How Colours are Produced
The colours in the fireworks are produced using different kinds of metal compounds. These metals are used in the form of salts. The reason behind this is because salts are way less reactive, they spread more and many salts can be kept easily together in the firework.
In a firework, colours are produced generally by two different mechanisms, called:
Incandescence is when the light is produced from heat. Certain substances when exposed to heat produce light. Thus, emits red, orange, yellow and white lights as the temperature is increased.
Luminescence is the light produced from energy sources that do not heat. The light produced by this process is called cold light as it can be produced at room temperature or even colder temperatures.
Different Colours of Fireworks
Different salts produce different colours when they are heated. The colours are actually because of the metals in them. This is because the metals give out different colours in the flame. This is an identification test for metals called a flame test.
Yellow colour in the fireworks is produced by sodium. Sodium is just not associated with your white coloured table salt. Rather when burnt, it gives out a bright yellow colour which is perfect for a beautiful explosion in the sky.
Strontium produces a red colour. Sodium in the natural state has a yellow colour but when it burns it produces a hot red colour.
The salts of barium give out a perfect green colour in the flame. While blue colours are made from copper salts. They are the most difficult ones to produce. White colour in the fireworks is produced from aluminium and magnesium.
Carbon has been used for ages to produce glittery golden chandeliers. Different combinations of salts can also give out other colours like a mixture of strontium and copper produce gorgeous purple hues.
Chemistry Behind Fireworks
The next time when you buy roman candles online or any other firework, remember how their colours are produced. For a firework to explode in different colours, a few things are required. Without the special effects, these things are an oxidizer, a binder, a fuel and a colour producer. A combination of fuel and oxidizer is what you need for any other kind of explosion as well. Fuel is the source of electrons thus have a lot of stored energy or potential energy. The oxidizer is the one that receives these electrons when the reaction happens.
This kind of reaction is called a combustion reaction and a lot of energy is produced when the fuel burns. Binder is there to help keep all the compounds together inside. So, the fuel and oxidizer mixture just needs a spark to react and produce energy.
In fireworks, gun powder or black powder is the most important component. It is the mixture of Sulphur, charcoal and potassium nitrate. Charcoal acts as fuel in the mixture and potassium nitrate acts as the oxidizer. Upon heating, this mixture explodes immediately and the reaction can be represented by the following equation:
6 KNO3 + C7H4O + 2 S → K2CO3 + K2SO4 + K2S + 4 CO2 + 2 CO + 2 H2O + 3 N2
The binder used along with the mixture is generally dextrin.