As temperatures approached 90 degrees on Friday afternoon, a group of more than 100 people—mostly students—converged on Krentzman Quad for an ice cream social. The staples were there: bowls, spoons, Hershey’s syrup, and sprinkles. But one key ingredient elevated the day: liquid nitrogen.

Yes, it was the annual Liquid Nitrogen Ice Cream Social, held each fall during Welcome Week. The event is sponsored by the College of Science and organized by the Northeastern student chapter of the American Chemical Society.

Among the student organizers were Lauren Bertino and Amy Andes, both S’18. They are second-year students, chemistry majors, and roommates, so it was fitting that they stood side-by-side Friday afternoon wearing blue lab coats and protective goggles and gloves as they whipped up the first batch of ice cream. The process involves “flash freezing,” and Bertino described the process the following way.

You start by putting cream, milk, and sugar into a bowl. Then you pour in the liquid nitrogen and continue stirring. The liquid nitrogen begins evaporating very quickly as steam starts to rise out of the bowl, and the liquid nitrogen—which checks in at minus 300 degrees below zero—instantly freezes the ingredients. As she put it, “You’re essentially flash-freezing milk, cream, and sugar.”

Bertino and Andes have conducted this experiment before with their student organization. The group holds regular meetings throughout the academic year, organizes field trips, and brings in faculty and outside scientists for discussions. Northeastern students also give presentations on what they’ve learned about chemistry from their co-op experiences.

“We learn so much,” Andes said. “It’s really intriguing to be part of something like this as an undergraduate.”

For Bertino, the liquid nitrogen ice cream social exemplifies the very reason she’s fascinated by chemistry. “I like being able to see what I’m doing actually happen right before my eyes. That’s the most intriguing part of chemistry, and that’s what is happening here today too,” she said.

Though the warm conditions weren’t exactly ideal for making ice cream, visitors still ate it up. “It tasted really good,” said first-year student Morgan Castle. “And it was interesting to watch the process too.”