Science Projects on How Popcorn Pops

Science experiments explain how a small kernel grows into fluffy popcorn

If popcorn did not pop its name would be inaccurate. How can a Popcorn not pop? Most fortunately the name correctly describes the nature of the food. Popcorn does pop and science can explain the how and why of the process.

Anatomy of a Popcorn Seed

The secret to the pop is in the structure of the seed. Make a poster to explain the anatomy of a popcorn seed. The seed consists of four parts. The outermost covering is a thin but hard shell called the pericarp. The pericarp can withstand great heat and temperature. Under the pericarp is the endosperm, the starchy nutrient for the embryo. Contained within the endosperm is water. It is this water drop that creates the steam within the seed. The third part of the seed is the germ, the embryo that sprouts when planted. The last part is called the tip cap and is the portion of the seed that attaches to the corn stalk.

How Popcorn Pops

Popcorn pops when the temperature reaches around 400 degrees. This turns the drop of water to steam. Steam expands. The rising pressure pushes against the pericarp, causing it to explode with a pop. The starch in the endosperm gets pushed out as a soft, puffy mass. This is the popcorn ready to eat. Make a poster explaining this process. Substantiate with an experiment. Take three bags of microwaveable popcorn. Microwave one bag for the length of time stated on the bag, the second for half the time and the third for time and a half. Empty the contents of the bags in separate bowls. Count and note the number of unpopped kernels. Does the number vary with the varying cooking time? State the correlations on the poster.

Examining Variables

Popcorn pops because of the steam created by the drop of water. Soak a handful of popcorn seeds (the non-microwaveable variety) in a bowl of water for a couple of hours. Then roast them in the oven or use a popcorn popper. For the younger children adult supervision is recommended. Does that make a difference in the number of seeds left unpopped? The answer is no. It is the steam created inside the pericarp by the drop of water in the endosperm that causes the seed to pop open. The pericarp is a very hard shell and will not allow water to enter. Will warming the seeds before popping help? Warm a handful of seeds before popping. Does that reduce the unpopped kernels? No. It increases their number. Warming the seed dries out the water contained inside. With no steam produced the seed will not pop. Take a handful of seeds and make a hole in each. What happens when you pop them? The hole allows the steam to escape. It cannot build up enough pressure, and the seeds will not pop.

Unpopped Kernels

Popping corn under various conditions shows that there will always be some unpopped kernels. Make a poster listing the reasons why a seed will not pop. The tip cap may be damaged allowing the steam to escape so enough pressure does not build up. The seed may be dry. Ideally the seed should contain between 13 to 14 percent moisture. Less than that and there will not be enough steam. If there is more moisture, the pericarp will split before the endosperm is fully cooked. The pericarp may be damaged. All these conditions prevent the proper build up of steam pressure.

References

• Tell Me Why?; Why does Popcorn Pop?
• Popcorn; What Makes Popcorn Pop?