Flame Testing Guide

Bonfire night

 

What’s inside a firework? The history and science behind the bang! 

Fireworks! That grand spectacle of sound and colour, loved by adults and children alike all over the world! 

With thousands of pounds spent on lighting up the skies for just a few minutes of entertainment, you might think that these are complex pieces of wizardry, requiring some in-depth science “mojo” to create the wonderful sights and sounds that we so enjoy. But you would be wrong!

Let us take you on a firework journey, where you can learn some of the history and science of fireworks, and then have some fun with a few firework-y demonstrations that your students can enjoy... 

Fireworks have an extremely long history in the world, with most people believing that it was the Chinese that invented them.  
 
The very first ‘firecrackers’ were pieces of bamboo stalks that were thrown into fires to ward off evil spirits. As the air pockets in the bamboo heated and popped, they made a cracking noise in the flames, and thus ‘bangers’ were born! This was thought to be in the second century BC, over 2000 years ago. 


Since then, Chinese alchemists started to develop these firecrackers into something more resembling fireworks. They added a mix of potassium nitrate, sulfur, and charcoal to act as gunpowder, which was then poured into the hollow bamboo, and ignited and sparkled in the flames – the first ‘true’ firework. 

Fireworks continued to develop and arrived in Europe in the 13th – 15th century, where they began to be used in religious festivals and holidays, adding a touch of awe and excitement, and more than a little mystery to the proceedings! 

The manufacture of fireworks also spread with Italy being the first European country to make them. Now of course they are used all over the world in festivals both religious and secular, from Diwali to the 4th of July independence festival! 
 
The science of fireworks: 

The black powder ‘gunpowder’ first used by the Chinese alchemists all those years ago is still used today, to act at the main source of energy in the firework. 


Once the fuse is lit, it burns toward the gunpowder mix and melts the sulfur component. The molten sulfur flows over the potassium nitrate/charcoal mix which ignites and very quickly produces large amounts of gas and energy in a small space, causing an explosion that forces the firework into the air. Knowing how surface area can affect the speed of reaction means that the speed and the amount of energy released can be controlled. (Increase the surface area of the gunpowder mix – by using a finer powder – will increase the size and speed of the explosion). So slow-burning fireworks can be made alongside some fast rockets! 


Adding metal salts into the mix that burn with different colours will give individual colour to the fireworks. This is because of the energy released as the metal salt heats up, causing electrons around the nucleus of the atoms to become excited and jump out of their ‘orbit’. As the electrons lose energy they fall back into their orbit around the nucleus and that lost energy is given out as light (of different wavelengths depending on the metal salt used). For example: Copper salts will burn blue, Strontium red, Potassium lilac, Sodium yellow, and Barium green. Adding magnesium will provide sparks. 
 
Read on to find out more.

Click the button below to see our guide to flame testing and flame test colours.

 

Flame testing is a fun and visual way to identify metals in a compound. Read more on the process by downloading our guide.

 

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