Pingpong Ball Science Lightens Tone Before Finals


She could have just lectured, talking about Gay-Lussac’s law, which raises the temperature and pressure of a gas that is held at a constant volume. But she had these pingpong balls, 4,000 in all, and this bottle of liquid nitrogen, which at room temperature turns to gas and expands – Gay-Lussac in action – and, to be honest, she had talked enough for a semester of CHEM110.

“On a day-to-day basis, chemistry can get a little tedious,” Tracy Halmi said. “There are a lot of calculations. And we often lose sight of why we do all those calculations.”

Halmi, senior lecturer in chemistry at Penn State Erie, The Behrend College, knew that her students would better remember Gay-Lussac’s law if they saw it put to use. So she and Jerry Magraw, a senior laboratory technician, poured some nitrogen into a 2-liter bottle.

“Let’s see what you learned this semester,” Halmi said. “As the temperature increases, what will happen?”

“It expands,” a student answered.

“It’ll explode,” another said.

Magraw capped the bottle, dropped it into a 55-gallon barrel, poured in the pingpong balls and hustled away.

“This is going to be violent,” he said.

The nitrogen warmed, the bottle burst and a geyser of pingpong balls shot up to the ceiling, knocking several tiles out of place.

The students applauded.

“Go study!” Halmi shouted as they filed out. “Go study for that final!”