Daniel DeMersseman | The Valdosta Daily TimesSeventh-grader Andrea Petty built an eco-cooler for the St. John School science fair. The eco-cooler provides cooler temperatures without electricity.

VALDOSTA — St. John Catholic School presented its school-wide science fair this week.

Daniel Holcombe tied for first place for seventh grade with an experiment to transform sound into light, then back into sound.

Holcombe played a radio connected by wires to a light-emitting diode. The diode lit up when he played the radio. When Holcombe held the diode up to the solar panel on a solar-powered speaker, it powered the speaker and the speaker produced sounds.

“I want to be an electrical engineer one day,” he said.

Andrea Petty placed second in seventh grade. Petty built an eco-cooler by cutting off the top halves of plastic two-liter bottles and inserting them into drilled-out holes in a wooden board.

When Petty used a blow-dryer to blow hot air through the cut-off bottles, the temperature came out the other side slightly cooler, and when she blew the hot air through the opposite end of the bottle, the air came out slightly warmer.

“In Bangladesh, they don’t have electricity so they use this (eco-cooler),” Petty said.

She said she got the idea when the power went out at her house one day after a storm and her family decided to try out an eco-cooler in their window.

Eighth-grader Kate Panizzi conducted an experiment to separate DNA from fruits and vegetables. Panizzi pulverized celery, an onion, and a carrot in a blender and combined each separately with an alcohol solution. Then, DNA material from each vegetable rose to the top of the solution.

“I’ve always been into criminal background stuff,” Panizzi said. She said she wants to work in the field of criminal background science one day.

“The entire school participated,” said Arlene Manning, St. John Middle School science teacher. “PhDs from VSU came by to judge our students’ science projects. Students had to write a research paper, too.”