Navigation
See how chemical reactions can create bright flashes and loud noises.
Have you ever wondered how a plastic stick can glow for hours without any batteries, or why fireworks make a 'boom' that you can feel in your chest?
Everything around us is made of chemicals, and those chemicals store energy in their bonds. Think of these bonds like tiny rubber bands holding atoms together. When a chemical reaction occurs, these bonds are broken and new ones are formed. If the new bonds need less energy than the old ones, the 'extra' energy has to go somewhere! In many reactions, this energy is released as heat, light, or even sound. When a reaction releases energy, we call it an exothermic process. In this lesson, we are focusing on reactions where that energy shows up as a bright flash or a glowing light.
We can think of the energy release as a simple math problem. If the starting energy is higher than the ending energy, the difference is what we see as light. 1. Starting Chemical Energy: 2. Ending Chemical Energy: 3. Energy Released:
Quick Check
When a chemical reaction releases 'extra' energy that was stored in bonds, what are two forms that energy can take?
Answer
Light and heat (or sound).
A glow stick is a self-contained chemical laboratory! Inside the plastic tube is a liquid and a small, brittle glass vial containing a second liquid. When you 'snap' the stick, you break the glass vial, allowing the two chemicals to mix. This starts a reaction called chemiluminescence. Unlike a lightbulb, which gets very hot, this reaction creates 'cold light.' The chemical energy is converted directly into light energy without making much heat at all. This is why glow sticks are safe to hold!
Let's compare how different items produce light: 1. Flashlight: Uses electrical energy from a battery to heat a wire or power an LED. 2. Glow Stick: Uses chemical energy stored in liquids to create light directly. 3. Sun: Uses nuclear energy to create heat and light.
Quick Check
Why do you have to 'snap' a glow stick before it starts to glow?
Answer
Snapping it breaks a glass vial inside, which allows two different chemicals to mix and start the reaction.
Fireworks are much more intense than glow sticks. They use a chemical reaction called combustion (burning). Inside a firework, gunpowder reacts rapidly with oxygen. This creates a massive release of energy in two ways: 1. Light: Scientists add different metal salts to the gunpowder. When these salts get excited by the energy, they release specific colors. For example, Strontium () creates red, while Copper () creates blue. 2. Sound: The reaction happens so fast that it creates a lot of hot gas. This gas expands outward so quickly that it pushes the air away, creating a shockwave that we hear as a loud 'bang!'
What is the term for a chemical reaction that releases energy into its surroundings?
In a glow stick, what type of energy is being converted into light energy?
The loud 'bang' of a firework is caused by the metal salts changing color.
Review Tomorrow
Tomorrow, try to explain to a friend why a glow stick eventually stops glowing. (Hint: What happens to the chemicals inside?)
Practice Activity
Next time you see a firework or a candle, identify if you are seeing light, hearing sound, or feeling heat, and remember that all three are forms of energy being released!