Even though the 4th of July is not yet here, I want to talk about fireworks, namely what makes them many different colors.

Firstly, let’s talk about what a fire is. You need an oxidizer, usually oxygen gas, fuel, and some starting heat. It is a special type of chemical reaction, combustion, which results in the production of heat. The reason you need some starting heat is to cause the fuel to start breaking apart in a process called pyrolysis. This starting heat adds the activation energy, which is the energy needed to kickstart chemical reactions. Pyro means fire, and lysis means to break apart. The carbon and hydrogen from the fuel react with the oxygen gas to create carbon dioxide and water. After a fire, the carbon particles that were released from the fuel join together again to make soot, and energy is released as heat.

Now for the light. Remember the starting heat I talked about in the beginning? That gets used here. The energy that is put into the reaction excites the outermost electrons, causing them to jump up an energy level. However, this position is very unstable, so they return to their normal position, and release light. This is because of the law of the conservation of energy, which states that energy cannot be created or destroyed. The breaking and reforming of chemical bonds releases energy, which is absorbed by other atoms, and re-emitted, leading to light.

Different flames have different colors. For example sodium ions, when they get excited, produce orange flames. Lithium ions create red flames. Copper ions create blue flames. Strontium ions also create red flames. These metal salt ions are what give fireworks their colors.

Different arrangements of these metal salts and black powder, called stars, results in different patterns of fireworks that can be created. Usually pyrotechnicians control the process , from the ratio used to make the stars, to the planning of the height of each firework. The sound of a firework depends on this ratio.