Popcorn popping should definitely be approximated by a normal distribution. Modeling it as a Poisson distribution requires us to ignore the real trait variability in things like size, shape, thickness of hull, etc., of individual kernels that will have an effect on expected popping time. Not to mention other sources of variability like the distribution of oil and salt in the pan, distance from the heating element, conductivity of the pan, etc. At the intersection of these a normal distribution is probably your best bet.
