WATERLOO - Superman: Beware. Spider-Man: Watch your back.

Cedar Valley kids are onto your superhero secrets. And on Tuesday, they had the chance to try their hand at the tricks of the trade at Bluedorn Science Imaginarium.

Youngsters crafted air-powered hovercrafts that scoot faster than a speeding bullet, mixed up a fresh batch of radioactive slime, and mastered the forces of magnetism a la Magneto Man. All in a single afternoon.

"I learned about how science works and how they use it," said Olivia Ofori, an 8-year-old from Miami visiting her grandparents in Waterloo. "It's pretty cool."

A few minutes later she chased after her hovercraft - a contraption constructed using a CD, empty film canister and pink balloon - as it slid across the floor.

"Whoa," she cried. "It's going with the air."

Imaginarium science educator Jason Dornbush laughed as he watched the girl's excitement, urging her to reinflate the balloon and repeat the process.

"From a teacher perspective, it makes science fun for kids," said the University of Northern Iowa education student. "But at the same time, they're learning about some pretty big concepts."

The hovercraft exhibit demonstrates physics concepts like force. Making glow-in-the dark sludge from glue and a sodium borate solution teaches kids about phases of matter.

And meeting Spider-Man's distant relative, Charlotte the rose-haired tarantula, allows kids to learn about the biology of invertebrates.

"Science of Superheroes and Supervillians" will continue through Friday. The hands-on exhibit is part of a summer series of "Weekly Wonders" programs hosted by the museum.

Past topics have included the science of sports, rockets, and the life of Civil War soldiers.

Next week kids can visit the Imaginarium to learn about flight. About 250 children attend the seminars each week.

Jan Young, of Elk Run Heights, says she often brings her grandson, Dallis Metsale, of Gilbertville, to "Weekly Wonders" activities.

She knew they couldn't skip this week.

"He loves superheroes," said Young, as the 5-year-old explored the exhibit. "But no matter what the topic, we always learn something."

Contact Mary Stegmeir at (319) 291-1482 or mary.stegmeir@wcfcourier.com.