Combustion is defined as the chemical combination of two substances accompanied by the production of light and heat; simply put, to combust is to burn. Take a look at this six-second video of one of our Education staff members, Isaac, conducting an internal combustion reaction:
As you can see in the video, Isaac starts by placing a few drops of methanol [methanol: oxidized methane, a main component of natural gas] into an oxygenated polycarbonate plastic bottle. The bottle has been punctured by two metal conductors, carefully angled so as to avoid any dangers should they become dislodged. After dropping the methanol in, Isaac corks the bottle.
Next, he takes a Tesla coil (powered by electricity) and touches it to the tip of one of the metal conductors. Within a matter of seconds, a burst of heat and light pushes the cork out of the bottle at high speeds.
What exactly is going on here? Ultimately, this is a demonstration of how electrical energy becomes chemical, then radiant and thermal, then mechanical energy. It’s the same concept that is behind how our car engines work – to power car engines, a cycle of hundreds of these explosions must occur per minute, and they must be converted into rotational, rather than linear, motion (think in terms of pistons and crankshafts).
In Isaac’s demonstration, the bottle is our closed chamber, the methanol is our fuel, and the Tesla coil serves as our initial source of energy. When Isaac puts the coil to the conductor, electrical energy is transferred to the metal. This energy wants to continue traveling along the path of least resistance, but there is a gap between our two metal conductors. The energy jumps this gap, yielding a spark which generates a chemical reaction between our oxygen and methanol. As the two react, they release light and heat; the heat causes the air in the chamber to expand. This expanding air is highly pressurized and must escape the container. Therefore, it searches for a means to do so – by way of our cork. The cork then blows off, showing us mechanical energy in action!
NOTE: In internal combustion chambers, the proper ratio of fuel to oxygen, known as the Air-fuel ratio, is crucial. This ratio determines the yield of your reaction.