Fourth of July has arrived in the United States, and we are excited to celebrate our nation's independence with some explosives....better known as fireworks! Fireworks are a symbol of the Fourth of July, so we thought it would be fun to cover the science of fireworks and what makes them explode with all that color!
There are a a few different types of fireworks but aerial fireworks are the ones designed to shoot high into the air and give us those amazing, patriotic shows that so many of us look forward to every year.
First, let’s talk about what makes up an aerial firework. A firework is held together by an outer container that is usually made up of paper and string. Pretty basic. Within the container, there are stars which are composed similarly to sparklers. Those are surrounded by black gun powder. Then, at the center, there is a bursting charge that is composed similarly to a firecracker and has a fuse that leads to the top of the aerial firework to allow for lighting.
To launch a firework, it is set on a mortar that normally has black gun powder in the center of it to assist with the lifting action necessary to turn a firework into an aerial firework. The shell design affects the outcome of the firework and some fireworks have multi-break shells to produce different effects, colors, and sounds when the firework explodes in the air. These can be composed by layering the composition detailed above in various ways within a single shell.
Now that we have covered the composition of the firework, let’s talk science!
Different elements are used within the stars to control 2 things: the rate at which the chemical reaction takes place and the final effect of that reaction in regards to color and shape.
To control the rate of the chemical reaction, chemists use larger grains of chemicals and don’t mix together the black powder as thoroughly as you would if you were using it for other purposes to slow down the reaction.
To get the coloring they want, a chemist has to choose the right elements. When an element releases energy, it releases it in the form of light, and each element releases a different color light. This light comes from releasing the energy stored within the atoms of an element. When atoms come in contact with light, their electrons become excited and move to a higher energy level. Electrons can not stay in an excited state forever though, and when the electrons are cooling down, they release a colored light dependent on the element. For an example, copper oxide emits a blue color when ignited, strontium chloride produces red,and magnesium and aluminum produce white. Red, white, and blue!
The shape is dependent on the construction of the shells. Where the stars are placed makes the most impact on how the firework will appear after the explosion!
Hope you learned a bit about fireworks — just in time for the 4th of July!