HOW DO FIREWORKS WORK?
Fireworks can be quite complex and different types (rockets, Catherine wheels, and so on) work in different ways. Simply speaking, though, aerial fireworks (ones designed to fire up into the sky) have five main parts. Working up from the bottom to the top:
The science of fireworks teachers love fireworks because they teach you about chemistry and physics within fireworks at the same time, in a very dynamic and colorful way!
Chemistry of fireworks exploding fireworks are essentially a number of chemical reactions happening simultaneously or in rapid sequence. When you add some heat to fireworks, you provide enough activation energy (the energy that kick-starts a chemical reaction) to make solid chemical compounds packed inside the fireworks combust (burn) with oxygen in the air and convert themselves into other chemicals, releasing smoke and exhaust gases such as carbon dioxide, carbon monoxide, and nitrogen in the process. For example, this is an example of one of the chemical reactions that might happen when the main gunpowder charge burns:
2KNO3 (potassium nitrate) + S (sulfur) + 3C (carbon in charcoal form) → K2S (potassium sulfide) + N2 (nitrogen gas) + 3CO2 (carbon dioxide)
What makes the different colors in fireworks? That's chemistry too! Fireworks get their color from metal compounds (also known as metal salts) packed inside. You probably know that if you burn metals in a hot flame (such as a Bunsen burner in a school laboratory), they glow with very intense colors— that's exactly what's happening in fireworks. Different metal compounds give different colors in fireworks. Sodium compounds give yellow and orange fireworks, for example, copper and barium salts give green or blue fireworks, and calcium or strontium make red fireworks.
Photo: Chemical reactions in the sky: different metal salts make the different colors in fireworks displays. Clockwise from top left: blue and green = copper or barium; red = calcium or strontium; yellow and white = sodium.
Physics of fireworks The solid chemicals packed into the cardboard case don't simply rearrange themselves into other chemicals: some of the chemical energy locked inside them is converted into four other kinds of energy (heat, light, sound, and the kinetic energy of movement)in the fireworks. According to a basic law of physics called the conservation of energy (one of the most important and fundamental scientific laws governing how the universe works), the total chemical energy packed into the fireworks before it ignites must be the same as the total remaining in the fireworks after it explodes, plus the energy released as light, heat, sound, and movement.
Physics also explains why a fireworks shoot into the air. The charge is little more than a missile. As it burns, the fireworks are powered by action-and-reaction (also known as Newton's third law of motion) in exactly the same way as a space rocket or jet engine. When the powder packed into the charge burns, it gives off hot exhaust gases that fire backward. The force of the exhaust gases firing backward is like the blast coming out from a rocket engine and creates an equal and opposite "reaction" force that sends the fireworks shooting forward up into the air.
If you look at the various fireworks photos on this page, you'll see another bit of interesting physics going on as well. Notice how fireworks always make symmetrical explosions? If one part of the fireworks goes left, another part goes to the right. You never see a fireworks sending all its stars to the left or a bigger series of explosions to the left than to the right: the explosion is always perfectly symmetrical. Why is that? It's because of another basic law of physics called the conservation of momentum: the momentum of a fireworks (the amount of "stuff moving" in each direction, if you like) must be the same before and after an explosion, so explosions to the left must be exactly balanced by explosions to the right.
Types of fireworks Surprise and variety are the key to any good fireworks display: if all the fireworks were exactly the same, people would quickly get bored. Although all fireworks essentially work the same way—combining the power of a missile with the glory of burning metallic compounds—there are lots of different types. The ones we've talked about so far are called rockets or skyrockets and produce the most spectacular fireworks displays high in the air. Catherine wheels and pinwheels work closer to the ground. They have a number of small fireworks mounted around the edge of a wooden or cardboard disk and make it spin around as they fire off. Roman candles blow out a series of small fiery explosions from a cylinder every so often. Firecrackers are fireworks designed to produce sound rather than light and they're often incorporated into the upper effects of rockets.
We think of fireworks as entertainment, but the same technology has more practical uses. Flares used by military forces and at sea work in almost exactly the same way, though instead of using metallic compounds made from elements such as sodium, they use brighter and more visible compounds based on magnesium and they're designed to burn for much longer. Even in an age of satellite navigation and radar, most ships still carry flares like these as a backup method of signaling distress.
Photo: Fireworks began as a military technology and they're still used by the armed forces today. Here, sailors on board the aircraft carrier USS Ronald Reagan are enjoying a July 4 fireworks display as they sail through the Western Pacific and Indian Ocean.
A brief history of fireworks Who invented fireworks? Here's our quick history lesson!
Fireworks shell making
inside a fireworks areal shell
Making Fireworks shells
What makes fireworks shell
Making retail fireworks
Quality check of fireworks
GLUING fireworks time fuse to fireworks
mixing chemicals for fireworks
Finished fireworks test