Apart from rotting your teeth and giving you the diabetes, sugar is pretty harmless, right? Wrong!
Not a lot of folks realize it, but sugar is actually pretty darned flammable. In its dust form (not powdered sugar, but rather as residual dust from the sugar processing, um, process), it’s combustibility goes through the roof. Literally, in some cases.
To teach kids about flammability/combustibility and demonstrate the science behind the potential dangers of seemingly nonhazardous substances, we present this handy dandy Demo Science science demo. Time to put the “explosion” in “experiment”! Wait…what?
Safety First. And Second. Better Make It Third, Too
Most of the experiments we offer up here at Demo Science are kid-friendly and safe, and we often encourage the reader to include their students in the demonstration. This is not one of those experiments; this one is serious business. Like, “check in with the fire department ahead of time just to give them a heads up” serious.
So, stand back, kiddies. Get out of your desks, sure, but stand back. Way back. And put on some goggles, the lot of you.
Okay, so for this one, you’ll need a tall, wide candle. Scented or otherwise is up to you, but if you’re gonna go scented, may I make a suggestion? Scented or un-, a glassless candle is best—just the wax, no jar around it. You’ll also need something with which to light said candle, fine confectioner’s sugar (ask the folks in the bakery at your local supermarket—they’ll know exactly where to find it), and a plastic squirt bottle, like a miniature version of the kind that classic, old-timey diners use for their ‘chup and ‘stard.
You should also have a fire extinguisher or at least a bucket of water on hand, just in case. Keep your fingers crossed and your head on a swivel, everyone!
Go outside if you can; if not, clear off a lab table or your desk completely, and move everyone and everything that you can back at least ten feet. Make sure your students are between you and the exit, and not the other way around, also just in case.
Light the candle. Make sure you stand back as far as you can for this part, also just in case again. Once it’s wick is burning nicely, use the squeeze bottle that you filled with confectioner’s sugar the night before (you’re so smart to think ahead like that) to spray a small blast o’ sugar two to three feet above and perpendicularly across the open flame. If done correctly, nothing will happen—though I suppose you could do it incorrectly in a number of ways and still nothing would happen, but good job either way.
Move your squirt point down a foot or so and repeat. Again, nothing should happen.
Move down again so that you’re pointing your sugar spray directly into the open flame. KERFLOOM!
This time you should’ve created a foot-long burst of flame that lasted but a fraction of a second. My oh my! Once your students have settled down (and Kevin has changed his shorts) continue with the sciency explanation.
The Sciency Explanation
The first two times you squoze your sugar bottle, the sugar dust had time to disperse before it reached the lit candle. The final time, it remained concentrated enough to become combustible. Fine sugar dust is always combustible, as are numerous other types of dust (coal dust, saw dust, corn dust, paper dust, even titanium dust!), but only becomes dangerous under the right conditions.
A combustible dust explosion will occur when five elements come into play simultaneously: 1) Fuel—in this case the sugar dust; 2) Source of ignition—here, the candle; 3) Oxygen—unless you teach science in a vacuum, you’re good; 4) and 5) confinement and dispersion of the dust particles—squeezing the bottle dispersed the sugar dust, and its proximity to the open flame was close enough confinement for it to catch fire (i.e., it didn’t have time to spread out like it did when you shot your sugar well above the candle).
That sure is some swell sugar safety science!