Why Does Corn Pop?

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I recently upgraded my oven from a regular OTG (Oven-Toaster-Grill) to a microwave. And, like any science buff with a new toy, I started experimenting with it immediately. The first thing I did was drill a hole through the roof. The second was microwaving my iPhone 6 to try the new WAVE feature of iOS 8. Of course, the next thing was to make popcorn so I could watch my friends argue over which was better – Mac or PC. It was at that moment when I came up with the most important question in the history of humanity… or at least close to it… Why does Corn Pop?Popcorn (2)

No movie seems worth watching without those crispy crunchy popped kernels, even if movie halls sell them for twice the price of your tickets, and the tub is empty by the time the movie even starts. But hey… it pops, so there must be something special about it. As it turns out, there is!

Inside a Popcorn

Anatomy of a Popcorn Kernel

Anatomy of a Popcorn Kernel. Source: Carolina.com

Popping corn is actually a special variety of corn, but before we go into the details, let’s have a look at the basic anatomy of a corn kernel (seed). There’s the outer shiny golden layer to every kernel, called the hull or pericarp. The inner starchy layer, called the Endosperm, helps provide food to the germ within. The germ is the developing plant embryo.

Popcorn (3)

Now, the unique thing about the popcorn kernel is that it has moisture locked inside it. When heated, this water turns into steam, and if you recall high school physics, things expand when they are heated. As it accumulates heat, the steam expands and pushes outward against the walls of the kernel. It exerts a pressure of up to 9 times the normal atmospheric pressure. This rapid expansion is beyond the capacity of the wall to hold, and will eventually lead to an explosion. Wait a minute, doesn’t that sound familiar? An enclosed water container being heated to generate steam that makes noise when the steam escapes?

Popcorn SloMo

Holy popcorn, Batman!!! Popcorn is Nature’s personal pressure cooker. Mind = Blown!


  1. Wikipedia
  2. Why Does Popcorn Pop? – St. Louis Community College
  3. How Popcorn Pops – About Education
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