Hello Science Fans!
Combustion powers our cars, launches our rockets, and even gives us the energy to perform tasks throughout the day. But what is required to perform a combustion reaction? The ACS’ very own Chris and Adam demonstrate the essentials of combustion in this easy, fun demonstration.
The Methanol Cannon
You will need:
- ~1 mL of methanol (Note: new EHS studies suggest pure methanol may be hazardous. We suggest using denatured ethanol from the drugstore as a safe alternative)
- a 1 Liter plastic Nalgene container with two nails driven in such that the nails are ~1/2 cm apart inside the bottle with the ends sticking out
- a piezoelectric lighter
- 2 wires with alligator clips at each end
- a ringstand with a clamp
- a heavy weight
- a rubber or cork stopper. We’ve also heard of this being done with ping-pong balls.
Use eyewear and a lab coat. Make sure your audience is at least 6 feet away. Do not point the “cannon” at anything breakable or at any one. Do not fire the “cannon” more than once in an hour. Do not use more than 1 mL of methanol. Read MSDSs for Methanol carefully and follow their suggestions for safe handling.
Start by telling your audience about the “fire triangle“; that fire requires three elements: oxygen, heat, and fuel.
- Demonstrate that you have those three elements in this reaction (the methanol, the spark, and the oxygen in the air), and when all three are together, you end up with a reaction.
- Ask your audience what they think will happen if you only combine two of those elements (correct answer: nothing). Feel free to add theatrics to this part, perhaps creating the spark in the bottle with no methanol and faking disappointment.
- Add less than 1 mL of methanol to the Nalgene bottle and swirl it around so it evaporates. Cap the bottle with the stopper and point it away from everyone. Attach the piezoelectric lighter to the wires with alligator clips, and attach those to the nails protruding from the Nalgene bottle.
- Then demonstrate that with all three elements, you get a bang by pressing the button on the lighter. If you time it right, you can have the reaction go off when you say the word “bang”.
Take a look at our video for our take on this. Feel free to comment as to how you think it could be done better!