Intro: How to Demonstrate Surface Area and Reaction Rate (Flour Bomb)
This experiment involves any flammable powder, a paint can and a lit candle. Inside the sealed paint can, a dangerous explosion occurs when an air suspension of a flammable powder is ignited. Put less than a teaspoon of lycopodium on a piece of filter paper positioned on a tripod and using a lighted splint show that the pile of the powder does not burn. Then take the filter paper with the powder in one hand and a lit burner in another and pour the powder into the flame from a height. The cloud of the powder burns rapidly in a very impressive flash. Some practice might be needed before the demonstration.
Then you can tell the audience about the danger of powder explosions and proceed to a scaled down model for this demonstration. Light the candle in the coffee tin or a paint can and quickly fit the tin lid. Quickly (before the candle goes out) blow into the hose to force the lycopodium into the candle flame, keeping your head well back. The resulting rapid combustion of the finely divided powder blows the lid off the tin.
Drill a hole in an empty paint can
Insert a tube and bend slightly upward inside the can (towards the lid)and place a small funnel in tube. Tape to hold upright.
Add a few grams of flour, or lycopodium powder or saw dust, etc
place a lit candle inside the paint can
hammer down lid
blow into the hose to disperse the powder
stand back and count fingers and toes