Chocolate Fountains are Great for Physics Lessons

Delicious, delicious physics

chocolate fountain
Study co-author Adam Townsend examines his research subject. ADAM TOWNSEND/HELEN WILSON

Chocolate fountains are mesmerizing. And anything that looks that beautiful and can cover ordinary food into chocolaty-covered goodness is a contender for one of humanity’s greatest accomplishments. But as it turns out, chocolate fountains are also valuable tools for exploring the physics of liquids.

In a new paper published in the European Journal of Physics, scientists at the University College London examined why sheets of molten chocolate slope inward as they roll down a fountain instead of splashing straight down. Though a seemingly frivolous goal, chocolate fountains are actually great tools for explaining the complex physics behind how some fluids move, Mary Beth Griggs writes for Popular Science.

Like molten lava, ketchup and oobleck, liquid chocolate is a non-Newtonian fluid that flows differently than substances like water and some kinds of motor oil. Many of these can be fun play with (except maybe for lava), but understanding how these fluids move can be challenging for young physicists.

"Apart from the fact that they’re super cool and delicious, from a scientific perspective, chocolate fountains provide a really nice introduction to non-Newtonian fluids," study co-author Adam Townsend, a Ph.D student at the University College London, tells Rachel Feltman for the Washington Post. In one handy device, a chocolate fountains forces the melted chocolate through multiple different conditions. 

Chocolate fountains work by pumping liquid chocolate up to the top of the structure, where it drips over a dome and then cascades in a sheet to the next dome. In the first step, pressure forces the chocolate up against gravity; in the second step, the chocolate thins out as it flows over a solid object (the dome). In the final step, instead of pouring over the dome’s edge, surface tension causes the chocolate to tuck underneath the dome and then drip down in a sheet.

"It's serious maths applied to a fun problem," Townsend says in a statement. "I've been talking about it at mathematics enrichment events around London for the last few years. If I can convince just one person that maths is more than Pythagoras' Theorem, I'll have succeeded. Of course, the same mathematics has a wide use in many other important industries - but none of them are quite as tasty as chocolate."

Scientific achievements sometimes come at a price—between the study and his lecture demonstrations, Townsend believes he has bought more than 100 pounds of chocolate. But luckily not all of that chocolate went to waste, as hungry students were often happy to help get rid of the sweets once his lecture finished.

"We want them to know that math is in places you don’t expect, it’s interesting, it’s worthwhile to study it," Townsend tells Feltman. "And it’s a nice thing, having a chocolate fountain at a lecture, because they come up afterwards wanting to eat some—and then they ask questions."

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