Every year, millions of people watch fireworks explode and brighten the sky. From dazzling reds to brilliant blues, fireworks hook audiences with their vibrant colours, intricate patterns and loud bangs. These displays are actually the result of fascinating chemical reactions. A combination of elements and compounds transform a simple explosion into a fabulous display of science and art.
In ancient China, fireworks were created using gunpowder. Since then, they have become increasingly sophisticated, with chemists and engineers creating new ways to produce complex effects. If we look into the role that chemistry plays in creating these breathtaking displays we can fully understand how fireworks work.
There are several key components in a firework shell. The first one is fuel which releases energy and burns. Then there is an oxidiser which provides the oxygen for combustion (a reaction which releases energy and heat). The oxidisers ensure the reaction is quick and efficient as fireworks explode so high above ground and oxygen levels are lower. Firework shells also contain colour producing chemicals, small pellets known as ‘stars’ and a fuse. In these stars are the compounds responsible for producing the colours.
The actual colours of fireworks are created through a process involving excited electrons. The explosion of a firework creates intense heat and provides energy to the atoms of certain elements. This then causes electrons to become ‘excited’ and move to a higher energy level. However, these electrons can not remain at this energy level for long as they are unstable. They eventually return to their original energy level and release the excess energy in the form of visible light. Different elements will release different wavelengths of light which appear as different colours to the human eye.
Specific chemical compounds are responsible for the various colours seen in fireworks. Orange fireworks are produced by calcium compounds and red fireworks are produced by strontium compounds. Sodium compounds can generate bright yellow lights and barium compounds produce green effects. Some colours are harder to produce than others such as blue fireworks created by copper compounds. This is because copper must be heated to an incredibly precise temperature, if it is too high or too low the colour may be lost entirely. Some fireworks are created by a mix of compounds such as purple fireworks which are created by mixing compounds that produce red and blue light.
Fireworks are not only famous for their incredible colours but also for their impressive shapes and patterns. People may assume these shapes are random however they are intricately planned. Inside a firework shell the stars are arranged in specific positions and when the shell explodes the stars are propelled outwards while maintaining their arrangement. This allows fireworks to produce rings, hearts etc.
The sounds produced by fireworks are also a result of chemistry. The loud bang we hear is due to a very exothermic reaction which generates hot gases that expand extremely rapidly. This expansion creates displacement of particles that travel through the air as sound. Different chemical compositions can also change the intensity of the sound produced, some fireworks produce whistles, crackles or hissing noises.
Aside from a wonderful display, fireworks can have environmental impacts. The explosions release particulate matter, smoke and chemical residue into the atmosphere. Some of these compounds may also enter soil and water disrupting plant growth and water filtration. As we become more aware of environmental issues, scientists are working to create more environmentally mindful fireworks. There is research into creating cleaner-burning fireworks that produce fewer pollutants while maintaining the beautiful colours. Another alternative is the use of drone light shows, they offer impressive visual displays without the same environmental concerns.
The chemistry of fireworks shows how scientific principles can be transformed into art. Every colour, sound and shape is carefully engineered through the selection of chemicals. What may appear to be a simple explosion is actually the product of complex chemical reactions. The next time you see a firework display light up the sky it may be worth remembering that behind the display lies centuries of scientific discovery and innovation.
Chloe Tohme