Studying how oil spills differ in freshwater versus saltwater earned three seventh grade girls first place at the St. Margaret Regional School science fair.

Grace Ripley and Cathryn Seafuse, both of Wareham, and Clare Downes of Pocasset won their grade division at the fair, held last month. With the win, they earned a chance to enter their project in the Massachusetts State Science & Engineering Fair, set for May 5 and 6 at the Massachusetts Institute of Technology.

Grace said her team was curious about the differences between oil spills in freshwater compared to saltwater and how that might affect cleanup efforts.

“Hopefully, our findings will contribute to helping people clean up oil spills and help any animals that may be affected during a spill,” said Grace.

For the experiment, the team substituted motor oil for coconut oil because their densities are similar, said Grace.

Results showed that the coconut oil spread much faster in saltwater compared with freshwater. In freshwater, the oil sunk to the bottom, leading the team to believe that may have environmental consequences.

“We realized oil could transfer to the groundwater,” said Grace.

One of the judges, a faculty member at Harvard Medical School, provided encouraging words for the team.

“He offered us a lot of advice and suggested performing the experiment multiple times to see if we came up with the same result,” said Grace.

Located in Bourne, St. Margaret Regional School is a private school that caters to students from preschool through eighth grade.