Complex sentence: As pressure builds, the steam expands and the hull can no longer contain the pressure, the kernel ruptures loudly--quickly turning inside out, expanding, cooling and finally setting in a popcorn puff 20 to 50 times the size of the original kernel.
Split into simpler sentences: As pressure builds, the steam expands and the hull can no longer contain the pressure. The kernel ruptures loudly--quickly turning inside out, expanding, cooling and finally setting in a popcorn puff 20 to 50 times the size of the original kernel.