Emmanuel Virot explains, carefully, why he believes popcorn bursts when it jumps:
Details, in writing, burst from the pages of the study “Popcorn: critical temperature, jump and sound,” by E. Virot and A. Ponomarenko, published in the Journal of the Royal Society Interface [12, 20141247 (2015)]. Virot contemplates popcorn at the Hydrodynamics Laboratory at École Polytechnique.
The study begins with the sentence: “Popcorn is the funniest corn to cook, because it jumps and makes a ‘pop’ sound in our pans. “