How does popcorn pop?Delaney T. 2012
The smell of popcorn popping is one that arouses the senses of both young and old and makes the mouth water for a tasty handful. It makes a cold day a little cozier and a movie a little more enjoyable. Just about everything is better with
popcorn and almost everyone loves it. It is one of the most enjoyed snacks of all time, but where did it come from and how does it pop?

Legends:
There is a legend that old-timers tell of a certain summer when it got so hot that the corn in the fields stared popping right off the stalks. The cows and pigs thought it was a snow blizzard and they lay down and froze to death.
In American Indian folklore, some tribes were said to believe that quiet, contented spirits lived inside of each popcorn kernel. When their houses were heated, the spirits would become angrier and angrier, shaking the kernels, and when the heat became to hot, they would burst out of their homes and into the air in a puff of steam.


Prehistory:
The oldest ears of popcorn ever found were discovered in the Bat Cave (a site known to have been used by cave dwellers practicing agriculture three thousand years ago) of west central New Mexico in 1948 and 1950 by anthropologist Herbert Dick and botanist Earle Smith, Harvard graduate students. They discovered layers of trash, and garbage which had decomposed over two thousand years. In the trash were 766 cases of shelled cobs, 125 loose kernels, 8 pieces of husks, 10 of leaf casings, and 5 of tassels and tassel pieces. The deeper they dug, the smaller and more ancient the cobs, until they reached bottom and found tiny cobs of popcorn in which each kernel was in its own husk. Among those prehistoric kernels, they found six that were partly or completely popped. These grains have been so well preserved that they would still pop. In fact, they took a few unpopped kernels and dropped them into a little hot oil to prove that they could still pop. They have been dated to be about 5,600 years old.
popcorn homeade diagram DT wiki.jpg
This diagram shows how popcorn pops.


How popcorn pops:
Only popcorn kernels can pop, and the secret is water. Each kernel contains a small amount of water stored in a circle of soft starch inside the hard outer casing. When heated to around 450*F, the moisture turns to steam, creating pressure inside the kernel. As the pressure builds, the casing eventually cracks and gives away, and the kernel explodes and pops, allowing the water to escape as steam and turning the kernel inside out. If you have ever
popped popcorn, you know that it explodes everywhere!

To keep popcorn from exploding everywhere, modern popcorn poppers usually have some way to keep the popcorn contained. There are air poppers, poppers made for the fireplace, bags designed as poppers for the microwave, foil pans designed for the stove top, and various machines that use heat and oil. Even though our






Boiling:
Boiling is a form of evaporation, and can be a gentle simmer or even happen explosively. Any liquid can boil, not only water. At ordinary low temperatures, water, left open to the air, gently evaporates from its surface. Its vapor resists a pressure, which at low temperatures is much less than the pressure of the surrounding area. The water also tries, through the methods of popping popcorn may be different, our methods really are not that different from long ago.

vaporisation of tiny bubbles, to evaporate inside, but these tiny bubbles of water vapor, at the low pressure it would have at these low temperatures, are immediately blocked by the much higher pressure of the atmosphere.
But when the water is heated and its temperature reaches 212 degrees Fahrenheit, its vapor pressure reaches the pressure of the air surrounding it, so the bubbles that form by evaporation inside of the liquid are no longer blocked. They grow to large size, rise to the surface, and there release their vapor to the air. That sometimes explosive evaporation that starts inside of the liquid is boiling. The bubbles are water vapor, maybe mixed with a little



parts of a popcorn kernal 9-26-12.jpg
This shows the parts of a kernel
Popcorn- a physical change or a chemical change:


The physical changes that occur when making popcorn is the same if you put the kernels into the microwave, an air-popper or a pan of hot oil. The white, fluffy popcorn that we enjoy is created during cooking. The inside of the kernel, known as the endosperm, blasts through the outer shell, called the pericarp.
How does heat cause this explosion? When the kernel is heated, some of the water trapped inside the endosperm turns into steam. Molecules in the gas phase have more energy and touch more frequently with the outer shell creating pressure. The endosperm also contains starch. When the kernel is heated, the starch becomes more liquid like jelly. At a certain pressure and temperature, the pericarp will suddenly break open and releases the pressure, steam, and starch. Air cooling causes the starch to dry creating the fluffy shape of popcorn. Meaning popcorn has major changes to the shape, and the release of water, but there is no major change in chemical structure.
It is no secret how to get the most popped corn from your kernels; you need just the right amount of water in the endosperm and a strong pericarp. You can try some simple experiments at home to test these kernels. In the first experiment, use a small sharp object (like a needle) to puncture the outer shell of kernels. Can you still make popcorn? In the second experiment, warm the kernels in an oven at 200°C for 90 minutes before trying to make popcorn. What did you observe? Very few of these kernels should pop because drying in the oven removed most of the water.



Glossary:

Endosperm- holds the starchy center
Evaporate-to turns into water vapor
Pericarp- the hard bottom part of the popcorn kernel





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Horton, werwa, zike , pat, eric,Dinah. Boiling . Columbus Ohio : national geo society , 2002. Print.

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Slow Motion Camera of How Popcorn Pops - Popcorn Popper. Youtube , Jan 4, 2009. Web. 2 Oct 2012.