Controlling purpose: To demonstrate the effects of liquid nitrogen on the compression of gases.
You'll need: A vat filled with liquid nitrogen, a balloon, a healthy pair of lungs.
Step one: Take a deep breath and inflate your balloon.
Step two: Tie the balloon so no air can escape.
Step three: Take the inflated balloon and stick it in the vat of liquid nitrogen.
Step four: Remove the balloon from the liquid nitrogen and observe the effects.
Step five: Wave the balloon around and observe the effects.
Step six: Write a lab report on what you have observed.
It's not a particularly difficult experiment, but the kids who come to watch Jim Zdunek like to watch the balloon as it is reduced to miniature size in the liquid nitrogen, then inflated as if by magic when it is removed. Zdunek is a robotics expert at Kraft General Foods, but spends some of his spare time as a volunteer teacher for the Chicago Academy of Sciences.
Disturbed by what he sees as an epidemic of scientific illiteracy, Zdunek will demonstrate some "really cool experiments" at the academy's Winter Carnival this weekend. "When I was growing up during sputnik time," he says, "there was a real rush to get people into things like engineering and sciences. But that kind of thing has died down. People aren't into space anymore. They don't see the Russians landing on Mars as a threat. They say, 'Let them have it.' But they don't realize that we're going to be cut down in other areas. We've got the Japanese and their technology, and they are just going to wipe us out. High-definition television is one example."
Zdunek as a child in Chicago's western suburbs sounds a little like Calvin in the Calvin and Hobbes comic strip. At age 12 he didn't just have a chemistry set; he had a terrarium and would attach electrodes to insects and observe their neural responses. He charted the data in notebooks. "People in the neighborhood kept away mostly. I was the only one on my block who actually kept living terrariums. I had a cricket culture. I had a roach culture--my mother didn't like that at all. She was pretty upset. They were wood roaches though, so they wouldn't come into the house, I don't think. I had robber flies. They are one of the largest flies in North America. They're real large and they're real ugly. They're long and skinny, so they're almost like a dragonfly. But dragonflies aren't true flies."
Zdunek is like a latter-day Mr. Wizard. The idea of his presentations is to make science interesting and accessible to kids. He will show them a piece of dry ice, spill water on it, show the billowing smoke, and explain that this process is used in making music videos. "I try to get the audience to wonder about certain things, like what temperature really is and who Fahrenheit was. I talk about an effect called regelation. That's a phenomenon of how pressure affects solid water. If you pressurize some ice, you lower the freezing temperature of it. So it actually melts at the point of contact. It's been theorized that that's how glaciers were formed--two smaller pieces got together and some pressure from a geological shift caused a melting and freezing effect, which worked to create a larger piece.
"It's also the reason people can ice skate," he explains. "The pressure of your skate pushes down on the ice and causes a thin sheet of water. Ice is not slippery. It's the water molecules interfaced in between the rail and the ice that are the slippery part."
Another lesson Zdunek likes to demonstrate is that of sublimation, the conversion of a solid into a gas. If it's cold outside, real cold, take a damp towel and stick it on your laundry line. Come out the next day and that towel will be really stiff. Come out a couple of days later and you'll find your towel's back to normal. Why? "It's because there's actually a sublimation effect of water molecules going back into the air."
For his ice experiment finale Zdunek uses a Glad bag and some liquid nitrogen. He takes a container of liquid nitrogen and sticks it inside the bag. Then he ties the bag and lets the liquid nitrogen spill around inside it. As the nitrogen evaporates, the bag starts to inflate until it becomes a big balloon. Zdunek smacks the bag and POOF! the kids in the audience get a big rush of cold nitrogen.
"I was always the best person to have as a lab partner in school," says Zdunek. "I had always dry-labbed the experiment a week earlier, and I had probably already done the experiment ten years before. My abilities in the lab are very good. But I never was really able to take my ideas and talk about them. This sort of thing, where I can talk to fifth- and sixth- and seventh-graders, it's a big step for me. And I hope that I'm helping out some kids along the way."
Zdunek will perform his experiments at the Chicago Academy of Sciences, 2001 N. Clark, from 12 to 3 on Saturday and 1 to 3 on Sunday. Call 549-0606 for more information.
Art accompanying story in printed newspaper (not available in this archive): photo/Jon Randolph.