On your mark, get set: Science!

Some of the best scientific experiments are the simplest. Think of Galileo dropping lead balls from the Leaning Tower of Pisa, or Archimedes working out the principle of specific gravity while lounging in his bathtub.

The noble tradition lives on with Linda Paparella, a sixth-grade science teacher from Harlem's Opportunity Charter School in New York City. Ms. Paparella works frantically over a collection of orange halves, wires, metal plates, and a stopwatch. Next to Paparella, three other young teachers – Woody Smith, Chris Baker, and Saber Khan – fuss with their own bizarre concoction involving a watermelon, lemon cake batter, and an ammeter (a device that measures electric current). These four teachers, along with four others, are competing in front of an audience for the coveted title of "Iron Science Teacher." The teachers are given everyday objects and asked to create a science activity for students – in about 10 minutes.

The competition, held at San Francisco's Exploratorium and webcast at www.exploratorium.edu, is modeled on the Japanese cooking show, "Iron Chef." On "Iron Chef," culinary masters are given one ingredient that must be the centerpiece of an elaborate meal, quickly prepared. On "Iron Science Teacher," competitors are told the ingredient in advance so they can develop an activity, but once they're on stage, they have only 10 minutes to assemble and present their science lesson.

"Iron Science Teacher started as a joke," admits Linda Shore, informal host and director of the Teacher Institute at the Exploratorium science museum. "It was just a one-time thing, but it was so popular we've made it a regular program."

Last Friday afternoon, Ms. Shore tells contestants that preparation time is over as a crowd gathers expectantly around the stage. The museum has attracted the usual mix of parents, children, and summer camp groups. Shore announces this episode's special ingredient: "Fruit!"

Paparella is first up. She tells the audience a tongue-in-cheek story about needing to time her sixth-graders as they ran races, but her stopwatch battery died.

"Then I remembered that a battery is just a storage place for electrons," she says, "and fruit is just a sack of water with a bunch of stuff in it, and in that stuff are some free electrons."

Paparella explains how pieces of copper and zinc, connected to the orange halves by wires, create a flow of free electrons. Once the wires are hooked up to the stopwatch, calculator, or buzzer – Eureka! Power! The audience cheers.

Paparella has brought a whole new meaning to the phrase "orange juice."

Next, children from the audience are enlisted to act out the roles of "grabby metal," "giving metal," and electrons, all holding a rope to represent the flow of electricity through the wires. To top off her show, Paparella hooks up her calculator to show the audience that it's possible "to do a square root with nothing but fruit."

Paparella is followed by the Smith-Baker-Khan team, two Californians and a Louisianian. They've concocted a lemon-cake-baking contraption using an electrical current jumping between two spoons powered by an electrical outlet hidden inside a hollowed-out watermelon. "We threw the watermelon in there just for the fun of it," Baker says.

As the team explains the principles behind electrical conduction, current, and voltage, the electricity flows between the two spoons stuck in the batter.

"It's smoking!" warns Shore.

"In Louisiana, if it's not smokin', it's not cookin'," retorts Baker.

The smokin' batter turns into lemon cake. Or partly into lemon cake. The mushy yellow mess would not pass muster on "Iron Chef," but on "Iron Science Teacher" it wins a round of applause.

" 'Iron Science Teacher' has become a very powerful way of showing that science is about simple materials and everyday things," Shore says. "It also shows the public that we have very talented science teachers out there."

Most of today's contestants are studying for four weeks at the Exploratorium's Teacher Institute. The Teacher Institute brings both middle and high school math and science teachers together for classes, projects, and a chance to compare notes. Many of the Institute's participants build smaller versions of the Exploratorium's interactive exhibits to take back to their students. And, of course, they can compete for greater glory on "Iron Science Teacher."

Today's contestants are from California, New York, Louisiana, and Arkansas – a number of them are from Arkansas, in fact. "Some are from rural areas and don't get many opportunities to work with other science teachers," Shore says.

The next contestant, James Arce, is from Arkansas. With the assistance of audience members Maggie and Nadine, he shows how to extract DNA from plant cells (squished strawberries) and animal cells (Maggie's spit) using salt, rubbing alcohol, detergent, and a couple of test tubes. With a Dr. Frankenstein flourish, Mr. Arce finishes by pretending to mix Maggie's DNA with the strawberries. He pulls out a plastic doll with strawberries replacing its hands and face.

"My very own strawberry blonde!" Arce says. Eyeing his creepy creation, he adds, "Maybe I'll put her up for adoption."

Like all "Iron Science Teacher" shows, this one is webcast live. Every episode is archived and accessible on the Exploratorium's website. Well, almost every episode. "We had to edit out one winner," confesses Shore. "It was a very dramatic explosion. Really popular with the audience ... but it was too dangerous. We knew every little kid would want to try it at home." Nothing blows up on this show.

Arce is followed by Melissa Lopez and Tammy Davis, who show how fruit can be boiled to make dyes for T-shirts. They use pipe cleaners and fluffy cotton to explain why the dye molecules are trapped by the fabric. The last contestant is Todd Bauleke of California, who shows how pigments like those found in fruit can combine to produce an artist's palette of colors.

The winner of "Iron Science Teacher" is chosen by the volume of audience applause. Will "Fruit Battery," "Electric Cake," "Strawberry Blonde," "Fruits to Dye For," or "Pigment Mixing" carry the day? It comes down to a clap-off between Paparella and Bauleke. In the end, Paparella's juiced-up stopwatch and calculator win over Bauleke's artistry. All the teachers are beaming.

"Science teachers really deserve applause," says Shore. "This show is one place where they actually get it."

• You can watch the next 'Iron Science Teacher' webcast live on July 21 at noon, PST, at: www.exploratorium.edu/iron_science

It's hard to pick the cleverest ingredients and science activities served up at the "Iron Science Teacher" competition since its debut in 1997, but here are a few examples.

Fruitcake. This special holiday edition featured a reenactment of Galileo's experiment on the Leaning Tower of Pisa (dropping different size fruitcakes, of course) and a model of the digestive system using fruitcake to dramatize constipation. But the victorious science teacher sat on a fruitcake and then drowned it in a bowl of water to show how density affects buoyancy. None of the activities involved actually eating fruitcake.

Golf balls. A carnival game became a physics lesson about conservation of energy as kids from the audience rolled golf balls on a metal track. The activity beat out a golf ball catapult and a biology lesson on fertilization in which a golf ball starred as a sperm.

Plastic bottles.Flying machines and a super-soaker squirt gun lost out to an elegantly simple "lung in a bottle" made from a plastic bottle (the chest cavity), two balloons (the lung and diaphragm), and a straw (the trachea).

Red tape. The only episode not filmed at the Exploratorium was a special webcast from Washington, D.C. The winner used static electricity to levitate a bit of shredded nylon tape, proving that, even in our nation's capitol, red tape has its uses.