Ever wonder why popcorn pops?
The answer to this question is related to the content "Vapor pressure", then see a definition for pressure:
Relationship between the force exerted in the perpendicular direction on a given surface and the area of that surface.
The mystery surrounding the popcorn was already discussed even by some American Indian tribes, they started to make it with the whole ear placed on a skewer and taken to the fire. In regards to popcorn popping, they used to say that the spirits lived inside each popcorn kernel. The spirits lived in peace, but when their "homes" were heated they were furious, making with the grain to jump and finally burst freeing the spirit, which came out in the form of a mist.
But what happens is much more concrete: The "explosion" of a popcorn kernel when heated is the result of a combination of 3 factors:
1. In addition to starch, the interior of the grain (endosperm) contains about 12% water;
2. The endosperm is an excellent conductor of heat.
3. The outside of the grain (pericarp) has great mechanical strength, is hard and rarely has flaws (cracks).
When the corn kernels are heated, the internal moisture (endosperm) is converted into steam, that is, it undergoes vaporization. At a certain point, the trapped air tries to expand and the molecules move so quickly inside the corn that this way press hard on the resistant walls until they break and the corn kernels explode and become larger than the kernel original.
The pericarp acts as a pressure cooker, preventing the escape of water vapor until a certain threshold pressure is reached. At this point, two things happen: the grain explodes, with a characteristic sound (pop!) and the starch in the endosperm abruptly swells, transforming into the soft white flake we call popcorn.
The popcorn explosion is nothing more than the expansion of water vapor inside the grain, this is the true scientific explanation for the popcorn burst.
Do not stop now... There's more after the advertising ;)
By Líria Alves
Graduated in Chemistry
Would you like to reference this text in a school or academic work? Look:
SOUZA, Líria Alves de. "Relationship between steam pressure and popcorn"; Brazil School. Available in: https://brasilescola.uol.com.br/quimica/relacao-entre-pressao-vapor-pipoca.htm. Accessed on June 27, 2021.
