Lycopodium Powder Fireball
Materials: ★★☆ Available in most school laboratories or specialist stores
Difficulty: ★★☆ Can be done by science teachers
Safety: ★★★ Only to be attempted with adequate safety procedures and trained staff
Categories: Combustion, Explosions, Reaction Rate, Science Shows
Alternative titles: Dust Explosion Demonstration
Summary
Lycopodium powder, when ignited in a pile, burns slowly due to limited oxygen contact. When dispersed as a fine dust cloud and ignited, the vastly increased surface area causes rapid combustion, producing a dramatic fireball or small explosion.
Procedure
Part A. Slow combustion
Place a small pile of lycopodium powder on a ceramic mat.
Ignite it carefully with a propane torch or lighter.
Observe that the powder smolders or burns slowly with only a small flame because oxygen contact is limited.
Part B. Dust explosion (paint can setup)
Prepare a paint can with a small lit candle inside, positioned opposite a funnel connected to tubing and a squeeze bulb.
Fill the funnel halfway with lycopodium powder and secure the lid of the can.
Step back and squeeze the bulb firmly (or in quick bursts) to disperse powder into the flame.
Watch as the powder cloud ignites, producing a fireball and often lifting or blowing off the lid.
Alternate method (fireball through funnel)
Scoop two spoonfuls of powder into a funnel attached to tubing with a mouthpiece.
Place a lit candle on a support such as an inverted beaker.
Position the funnel opening just below the flame and blow powder through it to create a dramatic fireball.
Caution: do not inhale powder; ensure audience is a safe distance away.
Links
Variations
Use different dispersal methods (squeeze bulb vs. blowing through tubing) to compare fireball size.
Compare lycopodium powder with other finely divided flammable materials such as flour or non-dairy creamer.
Conduct outdoors at night for maximum visual effect.
Safety Precautions
Lycopodium dust can irritate respiratory systems; some individuals may be allergic—perform at the end of class and avoid exposing sensitive students.
Always keep a fire extinguisher nearby.
Conduct the demonstration away from students; if indoors, ask students in the front row to move back.
Do not inhale the powder while preparing or blowing through tubing.
Tie back long hair and remove flammable materials from the area.
Ensure the can and apparatus are stable and thoroughly tested before use.
Dispose of burned powder in trash and wipe surfaces with damp paper towels to avoid airborne dust.
Questions to Consider
Why does a pile of lycopodium burn slowly, while dispersed powder explodes? (A pile has limited surface area in contact with oxygen; dispersal creates massive surface area and rapid combustion.)
What gases are produced in the combustion of lycopodium powder? (Carbon dioxide and water vapor, along with hot combustion gases that expand rapidly.)
Why do grain silos sometimes explode? (Aerosolized grain dust behaves like lycopodium powder, creating explosive conditions when dispersed in air and exposed to a spark.)
How does surface area affect reaction rate? (Greater surface area allows more oxygen contact, dramatically increasing the reaction rate.)