The Amazing Exploding Classroom

Some years ago, my older son enrolled – with some reluctance – in a summer chemistry camp. On the second day,  while conducting an experiment, he and his fellow students accidentally, um, set the building on fire.  Just a tiny sizzle, really, but one that resulted in evacuations, firefighters, and screaming sirens. He came home goggle-eyed: “Chemistry is the best science ever!

I remembered this moment during a visit to Mount Royal University in Calgary, Canada, where the chemistry department had invited me to talk about The Poisoner’s Handbook as part of an International Year of Chemistry celebration. In fact, it came back to me at precisely the time that chemistry professor Nathan Ackroyd was  telling me about a spectacular classroom demonstration that involved methanol, an empty jug, and a lighted match.

To prep for the demonstration, Ackroyd filled a five-gallon jug with methanol vapors (not a home project;  careful handling by a careful chemist required). Even though he was sure of the effect, he was a little worried about the next part of the demonstration – the part where he dropped a lighted match into the vapor-filled jug. During a test run,  he had just slightly charred the ceiling of his office.

“My hand was shaking a little and the first match didn’t drop in. The students all thought that was pretty funny – of course, they didn’t know why I was nervous.” The second match went right to target. The vapors ignited with a roar. Flames shot upward nearly eight feet toward the ceiling. The classroom had a 20-foot-high ceiling but the shockwave rattled the ceiling tiles and blew a nearby projection screen backwards.

“Everyone jumped backward,” Ackroyd continues.

Eventually, the flames died back as they consumed all the oxygen in the jug. But a fresh supply of oxygen rushed in and the fire made another spectacular leap. “It continued to pulse for two of three minutes.”  He did move a later demonstration outside to a campus green space; the fiery results led another faculty member, watching out a window, to summon the university police.

After the police determined that this was merely a chemistry professor and not a crazed arsonist, they requested that he please let them know in advance if he planned any further demonstrations.

“So what were you demonstrating?” I asked.

“I wanted to talk about the need for oxygen in a combustion. And I wanted to get at the concept of detonation velocity.  In any combustion reaction (visualize an explosion moving outward) there’s an expansion of heated gases.  If  Ackroyd had created a fast-moving expansion,  there wouldn’t even have been time for that flame to shoot upward from the jug’s spout.  The blast of pressure and heat would have just blown out the sides of the container. Comparatively, then, methanol combustion is relatively slow.

“And the third reason,” Ackroyd continues. “It’s fun!”

Truly, I love the way they teach chemistry today. When I was studying chemistry at college, the only exciting, flammable moments were provided by me. That is, I set my braid on fire in a bunsen burner. The post-doc overseeing the laboratory was unfazed, merely tapping me on the shoulder and asking me if I smelled smoke. (I hadn’t, actually.) True, the students surrounding me were entertained by watching me smack the sparks out of my hair. But that was merely a side show courtesy of an absent-minded student.

Today we have chemistry professors like Bassam Shakhashiri at the University of Wisconsin-Madison running a whole program titled Science is Fun. Shakhashiri – the incoming president of the American Chemistry Society (ACS) – puts on an annual holiday show for the public, a festival of chemical fireworks, that packs in hundreds every December. (Note: I also teach at the University of Wisconsin and my family has been among the pack.)

Bassam Shakhashiri sprays metal salt solutions to color a flame

Could we use more Ackroyds and Shakhashiris? Absolutely. No scientist, I believe, puts on a better show than a chemist, can better take an abstract idea like combustion velocity and make it vividly real. Obviously, such showmanship also carries with it real risks and I don’t mean to dismiss them here. The very properties that allow for a fiery demonstration also make this a profession demands great respect for the power of a chemical reaction.

So, I’m not advocating for a fire-department-on-call situation with chemistry lessons (despite the positive impression on my son). Rather, I’d like to express my appreciation – and yes, envy – of the kind a terrific show that a good chemist can create.  To admire the way that such scientists work to make research accessible – and memorable.   “Because science explains how the world works, we can talk about whatever we want,” Ackroyd says. So we might as well talk about something fun.”

As a further demonstration, I’ve put one of my favorite fiery chemistry videos here. It involves, I’m afraid, the sad, sad end of a gummy bear:

And you know that old saying – that we just don’t do it like they used to. I don’t think it holds true with chemistry classes. Today, we do them better.

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17 Responses to The Amazing Exploding Classroom

  1. CJ says:

    I had the great pleasure of working in the Chemistry Demos Dept. at the University of Oregon during my undergrad days. It was truly the best job I could have.
    If you go to, you will see a variety of demonstrations (videos and stills), and the science behind them. Some of these are based on Shakhashiri. Perhaps a safer demo for Ackroyd would have been “Ethanol Cannon”.

  2. Deborah Blum says:

    Oh, that sounds like fun. And thanks for a great tip. I could definitely do a follow up post with examples like the Ethanol Cannon. Even the name is great.

  3. There’s a physics professor at USC who does a demonstration where he walks barefoot on hot coals to demonstrate the principles of heat transfer. I try to catch it every year (when i hear about it in advance)

  4. Alisa says:

    My high school chemistry teacher would always do this experiment when her students were learning about oxygen and explosions:
    Grab a large metal tin, the sort with a pop-lid on top (eg from Milo or hot chocolate… we’re talking LARGE though). Make small holes – one in the centre of the lid, and one on the side right at the bottom.

    Stick a tube attached to a gas line for bunsen burners into the bottom and press down the lid so that it just sticks, but no more. Turn on gas, and once vapours start coming out the top hole, light them on fire and turn the gas off.

    The fire will burn, then sink down out of sight into the metal tin. As enough of the vapour burns, oxygen rushes in, and at one point the mixture is just in the right molar ratio for the gas to burn explosively – the shockwave forces the lid off the tin, which hits the ceiling with a satisfying clunk!

    Two favourite first year/special high school demonstrations at my university’s chem building are: 1. “Here is a balloon of oxygen. (set on fire) Here’s a balloon of hydrogen. (set on fire) Here is a balloon of oxygen and hydrogen in a perfect ratio for an explosion. Better cover your ears, the shockwave is STRONG!”
    2. Bubble hydrogen through a large dish of detergent/soapy liquid. Use a 3m long pointer to hold a lit candle way up high above dish. Wait for large clumps of bubbles to free themselves from the dish, hit the candle and turn into fireballs.

    Explosions are brilliant for getting people excited about chemistry. 😀

  5. Tim Oleson says:

    My high school chem teacher’s pyrotechnic demo of choice was igniting methane bubbles. She’d use a soap solution, an over-sized bubble wand (a bigger version of the ones that kids use to blow bubbles), and the bunsen burner methane feed to make the bubbles. When the bubble floated up toward the ceiling, she’d light it with a candle taped to the end of a yard stick (er, probably a meter stick…more appropriate for science class). The flames would fan out beautifully over the ceiling tiles and, amazingly, not leave any burn marks.

    Couldn’t find any YouTube videos showing exactly how she did it, but there are lots of others that show essentially the same thing.

  6. Matt says:

    During one of my first demos as a prof, I decided to oxidize some magnesium. It’s bright. It burns cleanly. And, it’s very impressive. The burning cleanly part was key for me, since the lecture hall doesn’t have a proper ventilation hood. So I go about my business of igniting the magnesium to an entirely rapt audience. As it’s burning away, the dish that I had the magnesium in cracks. It must have been defective …
    Anyway, the burning magnesium falls on top of a laminate desk (I told you this lecture hall isn’t the best equipped) and promptly sets the desk on fire. I ran to the fire extinguisher. Thankfully it worked. Unfortunately, the residue from the extinguisher set off the building’s smoke alarms. Everyone had to evacuate.
    Not bad for my first month as a faculty member …

  7. Richard Blaine says:

    Back in my days as a high school chemistry teacher, I used to do a demo in which I burned a mixture of potassium chlorate and breakfast cereal (in place of the gummi bear above) in an ordinary cereal bowl. First I would read to the class the Calorie content off the box label, and then touch off the magnesium fuse. The resulting flames would shoot up a meter or more out of the bowl. On a good day, just after the flames subsided, the bowl would crack in half dramatically.

    No one in my class ever forgot “Calories means heat.”

    I learned this demo from the TV show “Mr. Wizard,” the alter ego of Don Herbert, who regrettably died a couple of years ago.

    PS. Do not attempt this demo without good ventilation and an appropriate safety shield. Be sure there is nothing flammable in the vicinity, including the ceiling.

  8. Deborah Blum says:

    I absolutely love this example – thanks so much. Must do another post on this subject!

  9. Barbara says:

    Many years ago, my high school chemistry teacher was a young woman who was more comfortable in general science courses and felt out of her depth in chemistry. (She told us all this.) Not the greatest class, but it did produce one of my most durable science class memories.

    One day the teacher set a vary large beaker of water on the front bench and told us all to get up and move back against the walls. She carefully extracted a tiny morsal of sodium metal from a bottle, dropped it in the beakers, and dashed behind a barrier. It fizzled a bit and stopped. She repeated with a slightly bigger morsal. It fizzled slightly longer. Embarrassed, she dropped a substantial chunk of sodium into the beaker which immediately exploded. Broken glass and presumably slightly basic water sprayed everywhere. Perhaps surprisingly, no one was hurt.

    Despite that great chemistry day, I remain a biologist.

  10. Yud says:

    In my high school chemistry class, our teacher brought in three balloons: one with pure hydrogen, with with hydrogen and oxygen, and one with hydrogen, oxygen, and aluminum powder. The first one made a nice fireball, the next a nice explosion, and the last one made an even better explosion. The hydrogen and oxygen went “bang”, but with the aluminum powder it was a much deeper “boom” that you could feel in your chest.

  11. Pingback: Gummi Bärchen et chlorate de potassium, ne le faites pas à la maison… | PerrUche en Automne

  12. Casey says:

    Best. Explosion. Ever.

    If you’ve never heard of the “barking dog” experiment, you owe it to yourself to check it out at Periodic Videos

    I show this clip to my high school students every year and they love it. Wish I could do it in class without running the risk of losing my job because I blew up half of the class.

  13. Deborah Blum says:

    Oh, geez, I love this whole video. The guys from Nottingham are hilarious and, yes, best explosion ever!

  14. Deborah Blum says:

    This is a great description of a smart experiment. I caught myself imagining that boom in the chest.

  15. Dan Lurie says:

    My highschool chemistry professor did the same bottle experiment, but with rubbing alcohol, and with the bottle laid on its side pointed down the aisle between the rows of desks. Made for a really great land rocket.

  16. Uncle B says:

    The great hulking American Neanderthal, product of three hundred years of Corporate breeding from the biggest, dumbest, hardest working stock they could find in Europe, contents himself with things that go Bang! in the classroom, while the very hungry, and very prolific communist Chinese build a better nuclear reactor at Tsinghua University, and their government provides Billions of Yuan for developing a safer, cheaper Thorium fueled reactor – an area subject to patent laws in America and therefore taboo to students.

  17. Kevin says:

    I remeber this one form Mr wizard’s World too .. But in my head he also had a powder of some kind that he sprinkled on the ceral , and then got a squirt gun from very far away and when the liquid in the gun ( water I assume) hit the powder , then the ceral flamed up … I never knew what that powder might have been , I think he was talking about it being ” powdered Oxygen ” but this is 20 years ago , having seen it once , as it aired lol