Five budding scientists leaned over a glass beaker filled with a cloudy white solution yesterday morning, watching it intently.

Nothing happened.

"You think it will be a slow reaction?" asked Rhonda Reist, a high school science teacher who was helping the students with the experiment. "Or -- "

"Whoa!" the students exclaimed together, cutting her off. In a split second, the solution had turned jet black.

"Can you do it again?" asked 14-year-old Melanie Kabinoff of Boynton Beach, Fla.

"You can do it as many times as you want," Reist said.

She gathered materials the students would need to figure out how the experiment worked. But that task alone would be too easy. These were no ordinary students. They were among the 40 top young scientific minds from across the country who have come to Washington this week for the seventh annual Discovery Channel Young Scientist Challenge.

So Reist added a level of difficulty: Make the reaction occur to the beats of a song. The kids immediately started brainstorming.

"I have a lot of really good ideas," Melanie told the four other students in her group. "We're not going to break up. . . . We need to work together."

The competition began Sunday at the Cole Student Activities Building on the University of Maryland campus. The winner is expected to be announced tonight at an awards ceremony at the Discovery Channel headquarters in Silver Spring. First prize is a $20,000 college scholarship; second and third place will receive $10,000 and $5,000, respectively. All participants will pocket $500.

This year, the challenges were based on understanding the forces of nature. Students had to navigate a blimp through fog, simulate the cleanup of biohazardous waste and create their own tornado and tsunami. James Lee Witt, former director of the Federal Emergency Management Agency, is scheduled to pay a visit today to the young scientists, along with students from public schools in the District and Prince George's County.

Don Baer, senior executive vice president for Discovery Communications, said the company came up with the theme after a tsunami devastated Southeast Asia last year. And it has remained timely following the recent disasters along the Gulf Coast and in Pakistan.

"All of a sudden, this 'Forces of Nature' theme had a lot more relevance coming into the fall," he said.

Discovery bills the event as the largest national science competition for middle-schoolers. Baer said that drawing children into science at an early age is crucial to ensuring that America remains internationally competitive. He cited a study by the National Academies released last week reporting that 70,000 engineers graduated in the United States last year, compared with 600,000 in China.

Judging at the competition is based on skill as well as on more intangible qualities such as teamwork and communication. The 40 students worked in teams of five to solve the challenges, requiring that they interact with more than a Bunsen burner.

With video cameras, microphones and reporters trailing the students yesterday, poised to capture their eureka moments, the competition was no place for wallflowers. Discovery Channel is slated to televise footage from the event in December.

Joanna Guy, 14, a freshman at Southern Garrett High School in Oakland, Md., has already learned the importance of staying on-message. She earned a spot at this week's challenge with her eighth-grade science fair project in which she had a vested interest: "What do you expect: Does expectation of difficulty level affect student test performance?"

Her study found that students' expectations affect performance in a big way. Ignoring the cameras like a pro during a chat with one of the hosts for the TV show, Joanna said that she is applying that lesson to the competition. She and Melanie Kabinoff are both on the "gold team" and helped come up with a cheer to keep them pumped during the event:

G! G, what?

G! G-gold!

"If you go into anything with confidence, you can accomplish so much more," Joanna said.

Anudeep Gosal, left, Colleen Ryan, Iftin Abshir and Elijah Mena measure the wind velocity of a tornado they created as part of an exercise to help them understand the forces of nature.Sabrina Prabakaran, left, Taylor Jones, Alyssa Ovaitt and Brittany Sheehan collaborate to determine the densities of saline solutions as part of an experiment during the Young Scientist Challenge, which emphasized teamwork.