Going Out With a Bang
For a few lucky chemistry undergraduate students, the opportunity to blow up pumpkins and set gummy bears ablaze is all part of the job.
The student assistants know something is up when Professor Don DeCoste comes barreling into the chemistry prep room with a pumpkin under each arm.
"I knew he probably wanted to set the pumpkins on fire, but I wasn't sure at first," says Eric Szczesniak, a veteran at setting up demonstrations for chemistry professors such as DeCoste.
Szczesniak's hunch is right. To add pizzazz to a chemistry lecture around Halloween, DeCoste places a beaker of water into the pumpkins, which have been carved out with the traditional toothy grin. Then he dumps calcium carbide into the water, waits a few seconds for acetylene gas to build up, and sticks a candle into it.
POOF! Flames shoot out of the eyes, nose, and mouth of the two pumpkins. As if that isn't dramatic enough, all of the seeds that haven't been cleaned out of the pumpkins come pouring out of the pumpkins' mouths.
It is certainly enough to wake up any dozing students.
Concocting Colorful Chemistry Demos
If something is bright, turns colors, lights on fire, or explodes, there is a good chance that it has been used in a chemistry demonstration before a packed hall of students, says Szczesniak, a recent graduate in chemistry. Chemistry demonstrations have a long and colorful history on the U. of I. campus, but their success hinges on the behind–the–scenes work of a team of undergraduate students, scurrying around in lab coats, goggles, and protective gloves.
The students work their magic in the demo prepping room, a narrow room just off of the main lecture hall in Noyes Laboratory, a National Chemistry Landmark. The prep room, like the rest of the building, dates back to the early 20th century, and its walls are packed, floor to ceiling, with a well–organized army of chemicals.
Megan Craine, who graduated in chemistry in 2006 along with Szczesniak, is another stalwart among the four undergraduate assistants who prepare demonstrations for professors. She loves the work—although she also notes, "I never understood why the guys are so crazy about the explosions."
"How can you not love the explosions?" responds Szczesniak, who takes obvious delight in Big Bangs. But as both Craine and Szczesniak point out, there is more to the demos than blowing things up. The demos teach basic chemistry principles as well.
"Flaming Gummy Bears"—one of Szczesniak's favorite demos—shows just how much energy can be generated by one gummy bear. It is a classic "exothermic" reaction, which means it creates a lot of heat. To carry out this demo, the professor fills a test tube with potassium chlorate and heats it with a flame. Then, when the student assistant drops a gummy bear or Cheeto into the test tube, the snack is immediately engulfed in a bright ball of flame.
"It looks like a magnesium flare going off," Szczesniak says enthusiastically. "The chemical oxidizes the gummy bear—the same thing your body does when it is digesting gummy bears, only much faster."
Craine says one of her personal favorites is simply called "Soap Bubbles." But don't be deceived by its innocuous name. It creates plenty of noise.
With this demo, professors create a mass of bubbles filled with both hydrogen and oxygen. Hydrogen is lighter than air, so the bubbles float into the air. Then, using a candle on the end of a long pole, the professor touches the bubbles one by one and they pop with a reverberating bang and a flash of fire.
"There's no danger to it," says Craine, "but you can feel the shock wave in your chest. What's really cool is that all of the chalk comes off of the chalkboard."
Craine joined the demo team two years ago after talking to chemistry instructor Jesse Miller, who was hunting for candidates to concoct these potent mixtures. Word of mouth and professor recommendations are the chief ways that Miller finds students who are up to the task.
"I pick good people to work in this room because it's important for them to be able to think on their feet," says Miller. "There's nothing worse than going out and doing a demo and having it not work. It tells students that chemistry doesn't work, and it makes you look foolish. Nobody wants to look foolish."
Leaving Their Mark
The history of chemistry demos at the U. of I. goes back to the 1940s when chemistry professor Gil Haight ignited the tradition. Haight was known across campus for his annual Christmas Magic Show, in which he and his student assistants orchestrated a variety of dramatic displays. This annual show was just revived in 2005.
"In Gil Haight's days, he would always have a teaching assistant with a fire extinguisher next to him," notes DeCoste. But the students and professors are quick to point out that demonstrations today are safe and the precautions are many. In fact, they say the only real problem is the smoke from certain demonstrations, which sometimes triggers the smoke alarms, leading to a visit from the fire department.
Craine says that prepping demos gets extremely hectic toward the end of a semester when some professors will do an entire "demo review day" featuring a whole host of demonstrations.
"We're doing 20 to 30 demos on these days," she says. "We're all running around like chickens with our heads cut off; but it's fun because everyone is in here working together. Also, these are the coolest demos of the semester. The professors literally want to go out with a bang."
Craine and Szczesniak went out with a bang themselves, finishing their final demo review just days before putting on their caps and gowns for graduation. Szczesniak has moved on to medical school, where blowing things up is not encouraged; and Craine says she hopes to find an administrative position in a pharmaceutical company or other place that will value her chemistry degree.
At the very least, these seniors were able to depart knowing that they have left their mark on the U of I chemistry program—quite literally. After all, the demonstrations often leave very distinctive marks…on ceilings.
Just a Typical Day
As the student assistants discuss their favorite demos, DeCoste suddenly rushes into the prep room with a 2–liter, plastic pop bottle, wrapped in duct tape. He is doing a quick demonstration of the "Pop Bottle" demo for some visitors.
His 2–liter pop bottles are filled with hydrogen and oxygen, which just happen to be the same mixture that blew up the Hindenburg, the ill–fated German dirigible from the 1930s. In this case, however, igniting the gas causes the plastic bottle to blast off with a resounding POP! The bottle crashes into the prep room ceiling, leaving a tiny dent—only one among many dents and holes.
"We really need to start labeling those holes in the ceiling," Szczesniak observes. Then he returns to work, mixing chemicals for the next Big Bang.
By Doug Peterson