FILM CAN BLAST
Created by Dale Olive and Randy Scoville
Future Flight Hawai`i instructors
Demonstration at a glance:
A dark film canister has a few drops of rubbing alcohol added to it and shook to vaporize it. A small barbecue lighter is attached to the lid and used to spark vapor. The canister flies off with a loud bang.
These set-ups can be bought from commercial sources or made easily by buying a replacement lighter for a barbecue grill from a hardware store. Place a few drops of rubbing alcohol into the canister and shake to vaporize the liquid. Another alternative is to fill the canister and then pour it out. This saturates the canister with vapor. Sparking the vapor causes a loud explosion due to the rapid expansion of the gases.
Liquids burn at a slower rate than vapors because the exposed surface to the flame is smaller. A suspended droplet of fuel can burn around its entire 360-degree surface. This rapid expansion of gases pushes the lid one way and the canister the opposite due to Newton's third law of motion "Action/Reaction."
Those who live around grain elevators know of explosions due to tiny particles suspended in air. While the grain itself is fairly hard to light, suspended particles of it can burn around its entire surface causing massive explosions. In automobiles, fuel is burned more efficiently in a vaporous state in the engine rather than in a liquid state.
Communications: Hawaii Space Grant Office
This activity is featured in Future Flight Hawaii, a K-12 Education Project of Hawaii Space Grant Consortium.
FEB 27 2001.