Today’s experiment serves to illustrate the second most useful thing about chemistry.

The first thing, obviously, is that it serves to turn stuff into other stuff. The second thing is that is serves to store and release energy. Chemical bonds take energy to make and break. If you break some high-energy bonds, and make some lower-energy bonds, then the leftover energy has to go somewhere. It becomes heat, making all the nearby molecules vibrate faster, and if there’s enough of it it becomes light, giving off photons.

Such reactions are called exothermic, literally outward-heating, and they’re very useful for several reasons. They are self-sustaining once you get them started; you have to put in energy to break the initial bonds and get the reaction going, but once it starts it generates enough energy to break the next set of bonds for itself. They provide an easy way to be sure that something is happening and you’re not just going to be stirring some unreactive water for hours. And they give off heat and light, which are themselves very useful things.

Allow me to introduce you to rapid exothermic oxidation. For millenia, it has been the heat source of choice for the human race, at night and in cold places. It’s dangerous if not handled carefully, because many things in the world, including people, can undergo the same basic reaction. Anything based on hydrogen and carbon, which is most of the living world, but especially things like dry plant cellulose, can react swiftly and highly exothermically with the oxygen in the atmosphere to produce carbon dioxide, water vapour, and other more complex products depending on the exact makeup of the reactive matter.

Are you there yet? This is the Internet, telling you to set things on fire. Matches, candles, nothing valuable, dangerous, or belonging to other people. Be careful and be safe, and enjoy the raw, unscientific, gloriously practical reaction that is combustion.