So as this quarter comes to an end, of course I am scrambling to finish everything and feeling the stressed. So what better to relieve said stress? Popcorn, of course! After watching popcorn pop endless times throughout my life (especially the exciting Jiffy Pop!) I suddenly thought of the physics behind a kernel of popcorn popping tonight, so I decided to look further into it.
The purpose of microwaving popcorn or placing it over heat is to heat up the water inside of the popcorn kernel. Individual popcorn kernels have moisture trapped inside of its hull, and as it heats up, it begins to boil once it reaches 100 C. The boiling of the water inside of the kernel causes pressure to build within the kernel, since the water vapors gain kinetic and potential energy within the concealed kernel.
Not only does the water vapor cause a rise in internal pressure, but it also causes the starch within the kernel to soften and expand, creating even more pressure on top of the vapor pressure within the kernel. The wall of the kernel also begins to melt at such high heats, causing it to weaken as the pressure increases. The pressure at this point can be up to 9 times as high as the atmospheric pressure.
Under this massive pressure, the wall of the kernel bursts, and the starch explodes outward. Ever notice how not all kernels are popped in a bag of microwave popcorn? That's because the amount of moisture in the kernel needs to be just right for this explosion. If there isn't enough moisture, the kernel cannot build enough pressure to explode. If there is too much moisture, the wall of the kernel melts before the pressure is high enough for a good starch explosion.
Once the kernel explodes, the starch pressure immediately drops, and the steam carries a film of starch outward. This expansion of starch is what creates the explosion starch cloud we know as popcorn.
So there you have it! I overthought the simple popping of popcorn so you guys don't have to!
Until next time, Fizzix Community, until next time.