The Chemistry Behind Explosions: Fireworks, Combustion, and Reactions

Explosions might seem chaotic, but they are controlled bursts of chemical energy — especially when it comes to fireworks! From dazzling colours to the booming sounds, it all comes down to chemistry. In this post, we’ll explore how compounds like potassium nitrate, aluminium, and others are the masterminds behind these brilliant displays.

Fireworks: A Symphony of Elements

Every firework you see lighting up the night sky is a delicate dance of chemical reactions. At the heart of it all is a process called combustion, where a substance reacts with oxygen to release heat and light. For fireworks, the key ingredients are an oxidiser, a fuel, and various metallic salts that give off colours.

Potassium nitrate (KNO₃), also known as saltpetre, acts as the oxidiser. It provides the oxygen needed for the combustion process to take place. This substance is often mixed with charcoal and sulphur to create gunpowder, the explosive heart of many fireworks. When ignited, this mixture rapidly burns, releasing gases that build up pressure — this is what launches the firework into the sky!

Combustion in Action

Once the firework is airborne, a second chemical reaction occurs — this is where the real show begins. Inside the firework shell, small compartments contain metal salts and powdered metals. These burn at high temperatures to produce light and colour. Different elements give off distinct colours due to the way their electrons react to heat. For example:

• Strontium produces red flames.

• Barium creates green.

• Sodium yields yellow.

• Copper results in blue.

The brilliant flashes of light are thanks to aluminium or magnesium. These metals burn incredibly bright, producing the intense white or silver flashes that often accompany the colourful bursts.

The Role of Oxygen

Combustion relies on a steady supply of oxygen. In fireworks, oxidising agents like potassium perchlorate or potassium nitrate ensure that the reaction has enough oxygen to continue even in the absence of air (as they burn high up in the sky). This is why fireworks can sustain their explosive light show mid-air.

Boom! The Sound of Chemistry

The loud bangs and crackles of fireworks are also down to chemistry. The rapid expansion of gases created by the burning fuel causes a sudden shockwave, which we hear as the boom. Different chemicals burn at different rates, which is why fireworks can also make whistling or crackling sounds.

Controlled Chaos

What makes fireworks so fascinating is the careful control of these chemical reactions. If too much oxidiser is present, the reaction could be too violent. If there’s not enough, the firework might fizzle out. Firework manufacturers carefully measure each component to ensure a controlled yet spectacular explosion.

So, next time you’re watching a firework display, remember that it’s not just a pretty show — it’s chemistry at its finest! Whether it's the vibrant reds from strontium or the brilliant white of magnesium, every flash and bang is a result of carefully orchestrated chemical reactions.