Question: What makes popcorn pop?

Ian Cade answered on 13 Nov 2014:

Dried maize kernels contain a little bit of water, when they are heated above 100C the water boils and ‘wants’ to expand

… however the maize kernel is fairly gas-tight and contains the water vapour… and as the temperature rises the pressure rises… until the kernel splits with a pop

(when I do this I use butter and a fairly hot hob so I guess the temperature is somewhere between 150 and 200C)

Using this:

http://www.webqc.org/ideal_gas_law.html

I very roughly (guessing the size of a piece of maize and how much water might be in it) estimated that the pressure inside the kernel at 200C might be above 30 atmospheres… But whatever the actual value, it is usually enough to burst the hard casing of the maize!