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Five simple experiments demonstrate what makes popcorn pop.
corn, popcorn, percent, hypothesis, inquiry, science, pressure, experiment, steam, temperature, conclusion
Popcorn pops because each kernel has a tiny bit of water inside it. When the kernels are heated, the water inside heats up to the point where it exerts enough pressure to burst the kernel open. The soft material inside puffs up as it explodes.
You can present to students a simple experiment to prove that moisture is inside popcorn kernels. Use a test tube for this experiment. Place one kernel of popcorn in the bottom of the tube. Cover the tube with aluminum foil and poke a few small holes in the foil. Use tongs to hold the test tube as you hold it over a lighted candle. The students should be able to see steam escape. Where is that steam coming from? (The moisture inside the kernel turns to steam.) If you hold the popcorn over the candle for a few minutes, it should heat up enough to pop. (The pressure builds up inside the kernel until it bursts.)
The knowledge that water is inside each kernel of corn might lead students to wonder about some things Introduce the ideas below and challenge students to hypothesize what will happen and why. Have students record their hypotheses before completing each experiment. After each experiment, have students record whether they hypothesized correctly or not. If their hypothesis was incorrect, have them record what they learned.
Note: In each case below, students count out 100 popcorn kernels. Using 100 kernels enables older students to quickly and easily convert the number of kernels that pop or don't pop into percents.
Experiment 1: The Control Experiment.
Before students perform any experiments, have them first set up a control: Count out 100 popcorn kernels. Heat oil until it begins to smoke. Add the popcorn and let it pop. When the popping stops, count how many of the 100 seeds popped and how many did not pop.
Experiment 2: What will happen if there is more water inside the popcorn kernels?
Count 100 popcorn kernels from the same bag used in the control experiment. Soak the kernels in water overnight. The next day, drain off the water and pat the kernels dry. Have students hypothesize what might happen when the kernels are heated and why. Follow the same popping procedure used in the control experiment. When the popcorn is done, count how many of the 100 seeds popped and how many did not pop. Did the kernels with more water pop bigger or faster or better? (Or was the popcorn too saturated to pop?)
Experiment 3: What if the popcorn is heated at a lower temperature?
Count 100 popcorn kernels from the same bag used in the control experiment. Heat the oil in the popper to a temperature of only 250 degrees F. Have students hypothesize what might happen when the kernels are heated and why. When the popcorn is done, count how many of the 100 seeds popped and how many did not pop. Did the lower temperature pop the kernels bigger or faster or better? (Or did the lower temperature fail to heat the water in the popcorn kernels enough to pop them?)
Experiment 4: What if you warm the popcorn kernels before popping them?
Preheat an oven to 200 degrees F. Spread 100 popcorn kernels on a baking sheet and preheat them for 90 minutes. Remove the kernels from the oven and allow them to cool. (Alternative: Leave the popcorn sitting on a very sunny shelf for a few days.) Have students hypothesize what might happen when the kernels are heated and why. Follow the same popping procedure used in the control experiment. When the popcorn is done, count how many of the 100 seeds popped and how many did not pop. Did the preheated kernels pop bigger or faster or better? (Or did preheating dry up the tiny bit of water inside each kernel, so it would not pop.)
Experiment 5: What if you poke holes in the popcorn kernels? Will that help the heat get inside and pop the corn more quickly?
If you are doing this experiment with younger students, you might want to puncture the kernels yourself. Use a needle to make several tiny punctures in the outer covering of a handful of popcorn kernels. (Puncturing 100 kernels could take some time; you might prepare the kernels ahead of time or use 10 kernels instead of 100.) Have students hypothesize what might happen when the kernels pop and why. Follow the same popping procedure used in the control experiment. Did the punctured kernels pop bigger or faster or better? (Or did the holes let more steam escape and prevent pressure from building up inside the kernels?)
Popcorn production is an exacting process. The amount of water inside a kernel of popcorn must be quite precise, as was proven in some of the experiments above. Perhaps students will come up with additional experiments to test other popping hypotheses?
Check students' hypotheses and/or explanations of what they learned from each experiment. You might have students write a conclusion summarizing what they learned from the experiments.
Lesson Plan Source
National StandardsMATHEMATICS: Number and Operations
MATHEMATICS: Number and Operations
GRADES Pre-K - 2
NM-NUM.PK-2.3 Compute Fluently and Make Reasonable Estimates
GRADES 3 - 5
NM-NUM.3-5.3 Compute Fluently and Make Reasonable Estimates
GRADES 6 - 8
NM-NUM.6-8.3 Compute Fluently and Make Reasonable Estimates
GRADES 9 - 12
NM-NUM.9-12.3 Compute Fluently and Make Reasonable Estimates
GRADES K - 4
NS.K-4.1 Science as Inquiry
NS.K-4.2 Physical Science
GRADES 5 - 8
NS.5-8.1 Science as Inquiry
NS.5-8.2 Physical Science
GRADES 9 - 12
NS.9-12.1 Science as Inquiry
NS.9-12.2 Physical Science
Find more popcorn activities in Education World's article, Popcorn Isn't Just for Movies Anymore.
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