It’s a scientific fact that grapefruits are juicier than oranges, lemons and limes.

Well, maybe. But seventh-grader Celina Madden spent hours working on her experiment before reaching this conclusion and presenting her findings as part of an annual fair at St. Bernardine’s Catholic School.

“I like this, because I’ve never done anything with food,” Madden said.

Each year the Catholic school situated at the corner of Harrison and Marengo streets encourages its students to explore the world around them through science and history. The kids pick their own topics and attempt to answer one fundamental question through research and experimentation. At this year’s science and history fair, held Jan. 27, St. Bernardine students explored the 1968 Democratic Convention, the effect of music on house plants and the causes of the Black Hawk War in 1832.

A handful of students and their projects will go on to be judged in regional competitions hosted by the Chicago Metro History Education Center and the Illinois Junior Academy of Science. If successful there, students move on to a statewide contest.

Madden, an Oak Park resident, said she has always enjoyed her science classes and devoted her project this year to the juiciness of fruit. Her mother even used the leftovers to make desserts.

Teacher Theresa Szot oversees the science projects for the fair and is always interested in the topics kids choose to research. One year, a student was able to see actual iron filings on certain breakfast cereals while attempting to determine those cereals’ iron content.

“That caught me off guard,” Szot said.

On the historical side, Lori Krase said she learns something from her students every year when they research a facet of Illinois’ history. Through maps, field trips and other research the students must put together a coherent presentation that proves or disproves their assumption about a historic event. In each of the last six years, at least one of Krase’s students has gone on to compete in the statewide competition, she said.

“It puts them in the role of historian and forces them to find primary sources,” Krase said.

This year’s science projects will be judged in early March at the Museum of Science and Industry. Judging for suburban students’ history projects will be in late March in Naperville.