How do gas laws explain how popcorn pops?
The heat increases the inner pressure until it explodes (pops).
When heated, a gas (or the air) expands.
Heating the corn seed, the air inside it try to expand, but because the seed is hermetic, it only increases its pressure, until the inner pressure is higher than the seed shell resistance. At this point, it explodes (pops) and become delicious.
As the volume of the seed is constant, to keep the equality when temperature increases the pressure has to increase as well.