You HAVE to build one of these for your chemistry classroom. Your students are going to love this! At this site*, you can learn how to build a propane gun. In the video below, you can see the propane gun in action:
The construction of the propane gun is remarkably simple, costs around $60, and takes less than 30 minutes to build.
The basic features of the gun consist of a clear vinyl tube attached to a trigger start propane torch. By partially depressing the trigger for 3 – 5 seconds, the tube is filled with a mixture of oxygen and propane gas. Once the tube is filled, the trigger is completely depressed, which ignites the gaseous mixture at the end of the tube closest to the torch. A bright blue flame, indicative of complete combustion of the propane, appears to travel from the tip of the torch all the way through the tube. If the tube is fitted with a soda pop bottle (with a ¾” hole drilled in the bottom), a “whoosh” or “pop” is heard as the gas in the bottle ignites and is ejected out of the bottle.
I intend to use this contraption in my classroom to discuss combustion, expansion of gases, activation energy, and chain reactions. Let me know if you build a propane gun and use it in your classroom. Also, be sure to share in the comments what chemical and physical concepts you might teach your students when using this device.
*If you decide to build one of these, please use common sense. Be certain not to point the gun toward any person or object. Also carefully follow the construction and safety procedures listed in the instructions.