Glow sticks are chemical reactions waiting to happen! Most are made of an outer plastic casing with a small glass capsule inside. The outer tube is filled with dye, which determines the color of the glow stick, and a chemical called diphenyl oxalate. The glass within contains hydrogen peroxide, the same thing you might use to clean out a cut or scrape.
When you crack a glow stick, you break the glass inside. Its ingredients are then free to mix and react, releasing carbon dioxide and chemical energy, which is converted to visible light. The reaction takes some time, which is why the glow lasts a while. The ratio of compounds in a glow stick determines whether it shines brightly and briefly or more dimly for a long time.
Temperature is another great way to control chemical reaction speed. When we add energy by heating up the glow stick reactants, the molecules move faster and interact more often. Cooling the system takes energy away, literally slowing things down at a microscopic level. Clear containers of cold, warm, and boiling water give a great view of this chemical property!
The fourth flask, on the far left, contains liquid nitrogen. At -321 degrees Fahrenheit, this cryogenic substance is so cold that it actually stops the luminescent reaction, making the glow sticks go dark. We can bring them back to life by allowing them to absorb energy in a warmer environment.