hypothesis on popcorn

August 18, 2016

Explore the "POP" in popcorn

A bursting science project

By Science Buddies & Svenja Lohner

Can you pop any corn? Find the secret to making the best popcorn--with physics! 

George Retseck

Key concepts Physics Gases Plant science Food science

Introduction Do you like popcorn? It's not only a tasty snack but also fascinating to watch when it pops in the pot. Why does it do that? What makes the small popcorn kernel jump into the air and change its appearance? Where does the characteristic popping sound come from, and does every corn pop? There are many good questions about this simple snack. In this activity you will perform some popcorn science—and even get to snack on your results!

Background There are many corn varieties that can differ significantly from popcorn, which are not just dried kernels of the sweet corn we eat. Popcorn is actually a special variety of corn, and it is the only one that pops. The key to popcorn is the unique design of its kernels. Most importantly, its kernel consists of a very hard, mostly nonporous outer shell called pericarp. Inside the kernel there is not only the seed for a new corn plant but also water and soft starch granules that serve as a food source for the seed during germ sprouting. Although popcorn has been around for thousands of years, scientists only recently resolved the mystery behind the popping sound and the detailed mechanisms of how the popcorn bursts.

On supporting science journalism

If you're enjoying this article, consider supporting our award-winning journalism by subscribing . By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.

The reason why popcorn pops is the water trapped inside its kernel. If the kernel is heated to a high enough temperature, this water will transform into steam. Due to the hard and mostly nonporous shell, the steam has nowhere to go, resulting in a buildup of pressure inside the kernel. Once the pressure gets high enough and the temperature reaches about 180 degrees Celsius (355 degrees Fahrenheit), the kernel hull bursts and the popcorn is turned inside out. The characteristic popcorn consistency and white-yellowish foamy appearance results from the starch inside the popcorn kernel. With high temperatures, the starch gelatinizes and then expands with the rapid burst of the kernel. Once it cools down, the solidified flake we know as popcorn is formed. The characteristic popping sound does not originate from the cracking of the hull as originally thought but results from the vapor release after the kernel has cracked.

There are many different methods of preparing the perfect popcorn, including making different popcorn shapes, but all efforts fail if the kernels do not meet specific requirements: The ideal popcorn kernel has an optimal moisture content of about 14 percent and is popped at a temperature of about 180 degrees C. A common way to assess popcorn quality is its “popping yield,” which you can calculate by counting how many kernels pop versus how many remain unpopped when the kernels are heated. You can also evaluate popcorn quality by measuring kernel expansion, which means how big the popped popcorn flakes get. Check out the quality of your popcorn kernels in this activity and get ready to make some popping noise!

Adult helper

Pot with lid

Vegetable oil

Heat-resistant bowl with a lid

Unpopped popcorn (at least 70 kernels)

Sharp knife

Three small cylindrical glasses

Scale that can measure 0.1-gram increments (optional)

Water (optional)

Preparation

Prepare three piles of popcorn with 20 kernels each.

Ask an adult helper to carefully crack open the hull of all 20 kernels from one pile with a sharp knife. This is best done by making a deep cut into the softer white part at the tip of the kernel. The kernel should be kept whole (not split into pieces) but the hull should be cracked.

Set your oven to 350 degrees F. Place one pile of 20 uncracked popcorn kernels into a heat-resistant bowl and put them in the oven for about 30 minutes. Use the oven mitts when you take them out. Let them cool down to room temperature afterward. How do the kernels look when they come out of the oven? Did the appearance of the kernels change?

Keep the last piles of kernels as they are.

With the help of an adult put the pot on the stove and add two teaspoons of vegetable oil into the pot.

Turn on the stove and set it to high. (Make sure you never work on the stove without adult supervision.)

Put three of the extra popcorn kernels (not from your three piles) into the pot, close the lid and wait until they pop. You can swirl the pot a little in between so the kernels don't get burned.

Once the three kernels have popped, remove them with a spoon and turn the heat down to medium. Add the pile of 20 regular, untreated, popcorn kernels into the pot and swirl it slightly to cover all the kernels with oil. Tilt the lid on the pot so steam can escape but be careful not to let hot oil splash out of the pot.

Wait a maximum of two minutes until all the kernels have popped or the popping has stopped. After two minutes take the pot from the stove and remove all 20 kernels. Put them aside for now—don't eat them yet! Be careful—you might need to wait for them to cool before you can count them. How many of the kernels have popped? What size are the flakes? Are they big or small? What color are they? Are they dark, brown or yellow? Was the popping sound very loud?

Take the pot from the stove and replenish the vegetable oil if necessary. Again, add three regular popcorn kernels (not from your pile) and wait until they all pop. Remove them from the pot before you proceed.

Now, take the pile of cracked popcorn kernels (that you cut with a knife) and add them to the pot. Swirl the pot slightly and keep it on medium heat with the lid tilted on top.

Leave the pot on the stove for two minutes, swirling slightly in between, and observe what happens. Take the pot from the stove after two minutes and assess your popping results. Did all the popcorn kernels pop? How does this popped popcorn look compared with the previous batch? Do you notice any differences? How big are the flakes this time?

Repeat these three steps but this time use the 20 popcorn kernels that you had previously heated in the oven. How do they look after two minutes of popping? Are there any unpopped kernels? Do you notice any size or color differences compared with the other popcorn? If there are differences, why do you think this is the case?

Take the three small cylindrical glasses and fill each one with a different batch of your 20 popped popcorn kernels (regular, cracked and preheated). They should each contain the same amount of popped kernels. Place them next to one another so you can assess the different volumes of the popcorn flakes. Are all the glasses filled up to the same height? Which popcorn kernels expanded the most? Which were the smallest? Can you explain the differences?

Finally, you can sample the popcorn from each of your piles. Which popcorn tastes the best? Is one more chewy or crisp than the other?

Extra: Test to find the ideal popcorn popping temperature. Set your oven to 180–190 degrees C (355–375 degrees F) and put a heat-resistant bowl with a lid with 20 regular popcorn kernels inside. Swirl the bowl occasionally and wait long enough so that the popcorn starts popping. After the popping slows down and stops take the bowl out of the oven using the mitts and count the popped kernels. Did all of the kernels pop? Repeat the same experiment but this time set the oven to about 170 degrees C (335 degrees F). Wait exactly as long as it took to pop the kernels at 180–190 degrees C then take the popcorn out of the oven. How many kernels popped at the lower temperature? What can you infer from your results about the optimal popping temperature?

Extra: In addition to preheating the popcorn kernels, take another 20 kernels and soak them in water for a few hours, then dry them afterward. Because the kernels will take up some water during the soaking you will increase the percentage of water inside the kernel. Repeat the popping process with these kernels. Will they pop at all? How many of them pop compared with the other popcorn kernels? Are their flakes the same size or bigger/smaller?

Extra: Ideal popcorn kernels contain about 14 percent water. You can estimate how much water is in your kernels by weighing them (plus oil and pot) before popping and afterward. From the difference in weight you can calculate the amount of water that has been lost as steam during the popping process. Does it come close to 14 percent? How could your measurement be improved?

Observations and results Did you get some nice fluffy popcorn? With the regular popcorn that you popped you should have gotten some big fluffy flakes from all of the kernels. Once they reach the right temperature in the pot and the vapor pressure inside the kernels gets high enough they burst open and jump into the air producing a nice popcorn puff. It probably didn't even take two minutes for all of them to pop. If you popped the kernels that you previously cut and cracked open, however, the result should have been different. After two minutes you might still have had some unpopped kernels, and the ones that did pop didn't get that big. The cracked kernels produce much smaller flakes because when you damage the kernel’s outer hull, the water vapor that is created during heating can easily escape through the crack. Therefore, less pressure is built up inside the kernel, which makes it either not pop at all or reduces the flake size after popping.

With the last popcorn batch that you preheated in the oven you should have seen a similar outcome. The kernels probably changed color and turned from yellow to brown during heating. The flake size should have also been smaller compared to the regular popcorn kernels. Because the kernel’s hull is not completely waterproof, preheating the kernels for 30 minutes at low temperature causes some of the water inside the kernel to evaporate. It did not create enough vapor pressure to burst the hull, rather the water escaped the kernel through tiny pores in the hull. Because of this reduced water content, the pressure couldn't build up as high in the preheated kernels, compared to the regular kernels during the popping process, which ultimately leads to smaller kernels. If the water percentage in the kernel is too low, the kernels won't pop at all because there is not enough pressure buildup.

You should have easily seen the difference in popcorn size and volume once you put the kernels into the glasses at the end of the activity. Although you put in the exact same number of popped kernels, the glass with the regular popcorn should have been filled up much higher than the other ones—again demonstrating that these “ideal” kernels pop and expand much better.

Cleanup Clean all your dishes. Make sure to let the oil in the pot cool down before you add any water to it. You can eat—and share—all of your popped popcorn.

More to explore Physicists Reveal the Secrets of Perfect Popcorn , from The Washington Post Popcorn Physics 101: How a Kernel Pops , from Scientific American Popcorn , from How Products are Made The Science of Popcorn , from Carolina Science Activity for All Ages! , from Science Buddies

This activity brought to you in partnership with Science Buddies

• Science Notes Posts
• Contact Science Notes
• Todd Helmenstine Biography
• Anne Helmenstine Biography
• Free Printable Periodic Tables (PDF and PNG)
• Periodic Table Wallpapers
• Interactive Periodic Table
• Periodic Table Posters
• Science Experiments for Kids
• How to Grow Crystals
• Chemistry Projects
• Fire and Flames Projects
• Holiday Science
• Chemistry Problems With Answers
• Physics Problems
• Unit Conversion Example Problems
• Chemistry Worksheets
• Biology Worksheets
• Periodic Table Worksheets
• Physical Science Worksheets
• Science Lab Worksheets
• My Amazon Books

How Does Popcorn Pop? The Science of Popcorn

People have snacked on popcorn since at least 3600 BC in Mexico. But, not all corn works as popcorn. Here’s a look at the science of how popcorn pops and how it’s different from other corn.

How Popcorn Pops

The quick explanation of how popcorn pops is that heat vaporizes water inside the kernel, which builds up pressure until it pops the skin of the corn kernel.

However, there’s more to soft, fluffy popcorn than just breaking a corn seed. The kernel contains protein, starch, oil, and water, with a hard hull called a pericarp. Quickly heating the kernel to a temperature of 180 °C (356 °F) vaporizes the water into steam and produces enough pressure (135 psi or 930 kPa) to rupture the hull. At the same time, the heat softens the starchy part of the seed, basically turning it into gelatin or natural plastic. When the corn kernel pops open, the protein and starch gel expands into a foam, which cools into a soft puff that is between 20 and 50 times bigger than the original seed.

Popcorn needs a water content between 14 and 15%. Too much moisture leads to chewy popcorn (at best) or moldy popcorn (the worst-case scenario). Too little moisture won’t produce the pressure needed for the corn to pop. Sometimes over-dried popcorn can be rehydrated to get it to pop.

Rapid heating is necessary. It’s easy to pop popcorn in hot oil, an air-popper, or the microwave. But, if you put a layer of popcorn on a baking sheet and slowly heat it, you’ll get roasted or burnt corn and not popped corn!

What Types of Corn Pop?

Good popped corn requires the right kind of the corn and the right amount of drying. Most corn used as popcorn is the cultivated strain Zea mays everta . Some heritage strains of corn and maize also pop. Popcorn you buy at the store usually is yellow or white pearl-type corn, but both pearl and rice-shaped popcorn is available, in white, yellow, purple, red, and multi-colors.

Freshly harvested popcorn pops, but the result is chewy, dense popcorn. To get fluffy kernels, the corn has to be dried until its moisture content is between 14% and 15%.

Popcorn vs Corn Nuts

If you dry field corn or sweet corn so that it has the right moisture content, at best only a few kernels will pop. The kernel that do pop won’t be as fluffy as regular popcorn, plus they’ll taste different. However, soaking dried kernels in water for three days and then frying them in oil produces a snack akin to Corn Nuts.

Other Grains That Pop

Corn isn’t the only grain that pops when heated. Sorghum, quinoa, millet, and amaranth grain all puff up when heated as the pressure from expanding steam breaks open the seed coat.

• Hallauer, Arnel R. (2001). Specialty Corns . CRC Press. ISBN 978-0-8493-2377-5.
• Jenkins, Matt (November 2010). “Quest for Corn”. Saveur . Bonnier (133): 26, 28. ISSN 1075-7864.
• Lusas, Edmund W.; Rooney, Lloyd W. (2001). Snack Foods Processing . CRC Press. ISBN 978-1-56676-932-7.
• Smith, Andrew F. (1999). Popped Culture: The Social History of Popcorn in America . University of South Carolina Press. ISBN 978-1-57003-300-1.

Related Posts

It’s a wonderful world — and universe — out there.

Come explore with us!  

Science News Explores

Popping my own corny experiment.

Turn a fun snack into a scientific investigation

A new study showed that popcorn pops in an oven at 180 °C (356 °F). Here I describe how I attempted to confirm that.

B. Brookshire/SSP

Share this:

• Google Classroom

By Bethany Brookshire

February 26, 2015 at 9:00 am

This article is one of a series of  Experiments  meant to teach students about how science is done, from generating a hypothesis to designing an experiment to analyzing the results with statistics. You can repeat the steps here and compare your results — or use this as inspiration to design your own experiment. 

Popcorn is one of my favorite foods. I love its squeaky crunch and the taste of butter and salt. Popping my own corn on the stove top makes me think of relaxing with a book or settling in with a fun movie. And now, it also makes me think of science.

Scientists recently popped  corn in a conventional oven to determine at what temperature the kernels explode. Then they invited the rest of us to run tests to confirm that their findings. I took the challenge, but decided to use the stove top. And — spoiler alert — I got a different result! But that doesn’t mean their findings were wrong. And I’ll explain why.

The researchers found that in an oven, corn pops at 180 °C (356 °F).  At this temperature, water inside the tough kernels turns to steam. As that steam expands, pressure builds up inside the kernel. Eventually, it forces the tough outer wall of the corn to burst open. The researchers calculated that kernels should pop at the same temperature regardless of size.  

But most people don’t pop popcorn in a standard oven. They use a stove top or a microwave oven. That could make a difference.

When corn sits on a baking sheet inside a standard oven, the heat bathes a kernel from all sides. In a pan on the stove, the bottom of the pot (which makes contact with a flame or electric burner) will be far hotter than the air above it. Because a smaller kernel will have a greater surface area, a larger share of it may make contact with the pot’s bottom. And this could mean it heats — and pops — faster. 

That was my own hypothesis — an idea that I could test. At my grocery store, the white popcorn’s kernels tended to be smaller than the yellow ones. So I hypothesized that those white kernels should pop first.

I assembled my equipment: a stove, small scale, pot, cooking oil, timer, infrared thermometer — and, of course, some popcorn. That infrared thermometer measures the heat, or thermal radiation , released from a surface. (Infrared thermometers are easy to find and use. I got mine for less than $20.) Just aim the device at a surface (mine comes with a nice laser to help) and its screen will tell you the temperature of the surface it’s pointed at. It’s a great way to measure the temperature without risking getting your fingers burned.

Next, I weighed out one gram of white corn, and another gram of yellow. Then, I counted how many kernels were in each gram.

It’s important to run the steps of an experiment — even one as simple as this — many times. If you do it just once, you will never know if the differences you saw between test groups (here white and yellow corn) were likely due to chance. I need to make my measurements enough times to ensure I don’t claim my experiment didn’t work, when really it did. (I also want to make sure I don’t claim my experiment worked when in fact it didn’t.) I consulted a chart (specifically, Table 2 in this link) to find out how many times I would need to run my experiment to find a difference between the kernels, if one really exists. The chart suggested I should weigh each type of corn 26 times.

I wasn’t ready to invest that much time for a short study. So I ran a preliminary experiment — a short trial. It could tell me if my idea might work with more testing. I weighed five different random grams of corn. I counted how many kernels were in each gram. From that, I could determine how much, on average, each kernel weighed. Each yellow kernel was around a sixth of a gram. The white ones were around a tenth of a gram.

With my infrared thermometer in hand, I put a tablespoon of olive oil in the bottom of a room-temperature pot. Then I placed one kernel of white popcorn and one of yellow in the center of that pot. I was careful to place them very close to each other. I wanted to make sure they would receive equal heat. I cranked up the burner to medium-high and aimed my thermometer at the center of the pot. As I waited for the kernels to pop, I measured and wrote down the temperature every 15 seconds. Finally, I logged the time that each kernel exploded.

Afterward, I did the dishes, made sure the pot was completely cool, and started all over. Again and again, a total of five times. For each color of corn, I summed the five popping times together. Then I divided the sum by five to get the mean   — a number that represents the average popping time for each set (color) of corn. I then compared the average time it took for the yellow and the white kernels to pop.

It may look like the yellow corn (in the yellow bar at right) took more time to pop than the white corn. But so far, there still is a possibility that the difference I detected was due to chance. So unless I run these tests another 21 times, I can’t say with any certainty that smaller kernels pop faster than larger ones.

But look at the graph below. Temperature appears on the bottom line. It shows that both the yellow and the white kernels popped when the pot was more than 225 °C on the surface. That’s much higher than the 180 °C the scientists reported in their experiment.

So a pot on the stove needs to get hotter than the oven for the corn to pop. It is possible that the kernels still need to reach an internal temperature of 180 °C in order to explode. But because the pot is in the open air, the pot itself must get hotter before the inside of each kernel reaches 180 °C.

Oh, and yes, my preliminary experiment shows that it is probably worth popping some more corn. The smaller kernels look like they take less time to pop. If I do the experiment 21 more times, I should be able to tell if that difference is real, or if it’s just a lucky guess.

The scientists who wrote the popcorn paper would like many of us to try their experiment. The next time you pop corn on the stove, see if you can measure the temperature of the pot when that first kernel exploded. Was its temperature similar to mine? Or did you get something different? You’ll have to run your experiment many times to make sure your results are consistent. It’s a good excuse to do some science.

And enjoy some popcorn while you’re at it.

Follow Eureka! Lab   on Twitter

Power Words

(for more about power words, click  here ).

average     (in science) A term for the arithmetic mean, which is the sum of a group of numbers that is then divided by the size of the group.

cellulose    A type of fiber found in plant cell walls. It is formed by chains of glucose molecules.

hypothesis   A proposed explanation for a phenomenon. In science, a hypothesis is an idea that must be rigorously tested before it is accepted or rejected.

mean   (in mathematics) One of several measures of the “average size” of a data set. Most commonly used is the arithmetic mean, obtained by adding the data and dividing by the number of data points.

pressure   Force applied uniformly over a surface, measured as force per unit of area.

radiation (in physics) One of the three major ways that energy is transferred. (The other two are conduction and convection.) In radiation, electromagnetic waves carry energy from one place to another. Unlike conduction and convection, which need material to help transfer the energy, radiation can transfer energy across empty space.       

statistics   The practice or science of collecting and analyzing numerical data in large quantities and interpreting their meaning. Much of this work involves reducing errors that might be attributable to random variation. A professional who works in this field is called a statistician.

thermal    Of or relating to heat. 

Get Your ALL ACCESS Shop Pass here →

Popcorn Science Project

Popping corn is a real treat for the kiddos when it comes to movie night or in our house any morning, noon, or night! If I can add a bit of popcorn science into the mix, why not? Popcorn also makes for a fun popcorn science fair project or popcorn experiment. Get set to experiment with our easy microwave popcorn recipe, and find out why popcorn pops. Let’s make popcorn!

Popcorn Facts

Here are a few popcorn facts to start you off on the right pop! Did you know…

• Popcorn is made from a type of of corn kernel. It is the only type of corn that can pop!
• A kernel of popcorn has three parts: germ (the very middle), endosperm, and pericarp (hull).
• There are several varieties of popcorn including sweet, dent, flint (Indian corn), and popcorn! Can you guess which one pops the best? Popcorn of course because it’s hull has just the right thickness for the magic (science) to work!

The Science of Popcorn

All three states of matter are included in this fun and especially edible popcorn science project. Explore liquids, solids, and gases with yummy popcorn and find out what makes popcorn pop.

Inside each kernel (solid) of popcorn is a small drop of water (liquid) that is stored within the soft starch. Each kernel needs the right combination of moisture content and heat from an external source like a microwave to produce the awesome popping sounds.

Steam (gas) builds up inside the kernel and eventually bursts the kernel when it becomes too much for the hull to hold. The soft starch spills out into the unique shape you get to see and taste! That is why popcorn kernels pop!

💡 Corn kernels are also fun to use for this Dancing Corn Experiment ! Watch the video too!

Microwave Popcorn Recipe

This is a super simple recipe for making the best microwave popcorn!

Ingredients:

• Popcorn kernels
• Brown paper lunch bags
• Optional: Salt and Butter

How To Make Popcorn In The Microwave

STEP 1. Open a brown paper bag and pour in 1/3 cup popcorn kernels.

STEP 2. Fold the top of the bag down twice.

STEP 3. Place the popcorn in a bag in the microwave and cook on high for about 1 1/2 minutes.

Remove from the microwave when you hear the popping slow down so it doesn’t burn.

STEP 5. Add melted butter and salt to your heart’s desire.

Be careful when you open the bag as the kernels might still be popping and may be very hot.

💡Next, you will want to whip up some butter in a jar to go with your microwave popcorn!

More Fun Kitchen Science Activities

• Shake up some homemade butter
• Make bread in a bag
• Try this melting chocolate experiment
• Write secret messages with cranberries

Turn It Into A Popcorn Science Project

For younger children….

Make sure to include the 5 senses when you put together this popcorn experiment! Ask the kiddos questions along the way. Making popcorn is a great way to explore the 5 senses.

💡 Check out more fun 5 sense activities for preschoolers!

For older kiddos…

Here’s a couple of quick ways to take this popcorn science project from an activity to an experiment! Remember a science experiment tests a hypothesis and usually has a variable.

💡Learn more about the Scientific Method For Kids and using variables .

Here are several popcorn experiments to choose from.

• Will the same amount of kernels yield the same amount of popped corn each time? Make sure to use the same measurements, same brand, and same set up for each bag and run three separate trials to draw your results.
• Which brand of popcorn pops the most kernels?
• Does butter or oil make a difference? Pop the corn with and without butter to see! You will need to run several trials to gather enough data. (More bags of popcorn to taste!)

What other kinds of popcorn science experiments can you think of?

Helpful Resources For Your Science Fair Project

Science projects are an excellent tool for older kiddos to show what they know about science! Plus, they can be used in all sorts of environments including classrooms, homeschool, and groups.

Kids can take everything they have learned about using the scientific method , stating a hypothesis, choosing variables , making observations and analyzing and presenting data.

Want to turn one of these experiments into an awesome science fair project? Check out these helpful resources.

• Science Project Tips From A Teacher
• Science Fair Board Ideas
• Easy Science Fair Projects

Printable Thanksgiving STEM Activities Pack

STEMS-Giving Pack! A full menu of Thanksgiving dinner science activities, secret codes, and more!

What’s Included:

• STEMS-Giving! A feast of science and STEM with simple experiments and projects for home or classroom!
• Even More Thanksgiving theme STEM activities with printable sheets, instructions, and useful information all using easy-to-source materials and perfect for limited time needs. Includes a Thanksgiving theme engineering pack with fun, problem-based challenges for kids to solve!
• Got STEAM? Try a turkey in a disguise challenge with writing prompts and more! Also color by code turkeys in disguise!
• Try your hand at building shapes with cranberry structure challenge cards.
• Discover Thanksgiving brick-building challenges perfect for early finishers, quiet time, hands-on math, or family time.

Study digs into the science of what makes popcorn pop

Microwavable packets and brimming machines at the cinema make popping corn seem like a simple undertaking, but there are number of factors that turn rock hard kernels into crunchy puffs of buttery goodness. Researchers digging into the science behind popcorn expansion have shed new light on the process, which could inform the breeding of higher quality corn down the track.

“The way kernels expand is a basic, yet very important characteristic of popcorn,” says Fernanda Maioli, a scientist at Brazil's State University of Maringá and study author. “Very hard grains burst when heated. This expansion multiplies the initial volume of the grains by more than 40 times. In the case of popcorn, it produces a unique and tasty food.”

Previous research has delved into the science behind the "expansion ratio" of different popcorn varieties and unearthed interesting insights, such as a relationship with the corn's starch content and its propensity to pop, or that factors such as kernel moisture can influence the end product.

Maioli and her colleagues studied 49 different types of popcorn, assessing things like kernel length, the amount of protein they were packing, how thick the coatings were around the kernel and the outer seed, and how well they are able to transfer heat during the popping process.

"We observed how this heat transfer inside the popcorn kernel relates to the expansion ratio," Maioli says. "It allowed us to understand how other characteristics may also relate to expansion."

The team's analysis uncovered a new correlation between the thickness of the kernel's outer layer and its potential to pop. The scientists hope to build on this by uncovering other relationships between characteristics of corn that could maximize its popping potential, with a view to breeding higher quality forms of the widely popular snack.

"The purpose of our study was to identify popcorn characteristics related to expansion," says Maioli. "This will help us efficiently identify popcorn varieties with good agronomic characteristics as well as good popping quality."

The research was published in the Agronomy Journal.

Source: American Society of Agronomy

Most Viewed

Saudi arabia seeks to silence neom project doubters with images and video, video: google robot paddles human table tennis competitors, expandable camping pod turns barren ground into rv-style kitchen.

The Science of Popcorn

Introduction

Popcorn is one of the world’s favorite snack foods. In the US, Americans consume as much as 18 billion quarts of popcorn each year, which equates to 56 quarts per person. Some nutritionists call it a perfect snack food because it is a whole grain, a good source of fiber, and low in fat. One study even claims there are more antioxidants in popcorn than in some fruits and vegetables. 1

The most intriguing part of popcorn is the science behind how it pops. Popcorn is the only grain in the corn family that pops open when exposed to temperatures above 180° C. A popcorn kernel is composed of 3 parts: the pericarp, germ, and endosperm. See Fig. 1.

The pericarp is the tough outer shell surrounding a popcorn kernel, and the key to what makes it pop. Inside the pericarp is the germ, or seed embryo. Adjacent to the germ is the endosperm, which contains some trapped water plus soft and hard starch granules that serve as food for the germ when it sprouts.

When a popcorn kernel is heated, the trapped water in the endosperm turns into steam, building up pressure inside the pericarp. This pressurized, super-heated steam transforms the soft starch in the endosperm into a gelatinous material. Popcorn pericarp is much stronger than that of all other corn kernels and is able to retain this pressurized steam up to 9.2 atm (135 psi).

Above that pressure, the pericarp ruptures, releasing the steam and gelatinous starch that solidifies upon cooling. The resulting popped kernel is 40 to 50 times its original size.

People often wonder what is the ideal percentage of water in popcorn kernels for best popping. Popcorn is harvested in the fall when the kernels’ moisture content is between 16 and 20%. The kernels are then stored in bins where they are dried by forced air until reaching an optimum moisture level of 14%. If the moisture content drops below that value, the size of the popped kernels is smaller and the number of kernels that pop decreases.

Inquiry activity

Popcorn is a great real-world example to use when discussing the kinetic molecular theory of gases, the phase change of water from a liquid to a gas, Gay-Lussac’s gas law (pressure directly related to temperature), and the ideal gas law ( PV  =  nRT ). After covering the gas laws in class, complement the lesson with an inquiry activity using several brands of popcorn. Have student lab groups devise a lab procedure to determine the following and submit it for your approval:

• Determine the % of water by weight for 20 kernels of each brand.
• n  = Moles of water lost (g water lost after popping ÷ 18.0 g/mol)
• R  = Ideal gas law constant (0.0821 L-atm/molK)
• T  = Boiling temperature of cooking oil in Kelvin (225° C + 273) = 498 K
• V  = Volume of 20 kernels (determined by displacement of 5 mL water in a 10- or 25-mL graduated cylinder.)

Materials (for 30 students working in pairs)

• 15 Beakers (250 mL)
• 15 Graduated Cylinders (10 or 25 mL)
• 15 Wire Gauzes
• 15 Ring Stands (with iron rings)
• 15 Bunsen Burners or Hot Plates
• 15 Weighing Boats

Have the following materials available at a central location: Cooking OilMedicine Droppers (or disposable plastic pipets)Popcorn (several brands)Aluminum Foil (for loosely covering the beakers)

Students should wear goggles and aprons or lab coats during the activity and exercise due caution around Bunsen burners or hot plates. Inform students that cooking oil boils at a higher temperature than water (225° C) and have them cover their beakers with aluminum foil to contain the popping corn and boiling oil.  Note:  Remind students not to eat any of the popcorn produced in the lab.

Helpful hints

• Students should add just enough oil to cover the bottom of their beaker before adding the 20 kernels of popcorn.
• Mass 20 kernels in a weighing boat and subtract out the weighing boat’s mass.
• Mass the beaker, oil, and 20 kernels before heating and without the foil covering.
• Mass the room temperature beaker, oil, and popcorn after heating and without the foil.

Sample data

Sample calculations

• % of water in kernels = water lost ÷ mass of kernels x 100 0.20 g ÷ 2.10 g x 100 = 9.5%
• Pressure inside of kernel prior to popping  PV  =  nRT P  =  nRT V P  = (0.011 mol) (0.0821 L•atm/mol•K) (498 K)                                    0.0015 L P  = 3.0 x 10 2  atm

Conclusion/discussion of errors

Most literature cites popping pressure as 9.2 atm (135 psi). If you choose to give your students that value, have them look at their measurements and see where some weaknesses may lie. An obvious weakness is the number of popcorn kernels. The more kernels used, the more accurate the measurements for volume and loss of water will be due to more significant digits. The temperature of the boiling oil is assumed to be 225° C, and the kernels are assumed to all pop at the same temperature.

Resource: American Chemical Society, “Popcorn: The snack with even higher antioxidants levels than fruits and vegetables”

Related Items

• Author Profile
• Posts by the Author

Calibrating pH Meters

• 3 Steps for Opening Your Classroom-OpenSciEd

Bioscience Core Skills Institute

Measuring mass.

• Three-Point Linkage with Drosophila
• Lumbriculus: Contraction Rate of the Dorsal Blood Vessel

Carolina Staff

Carolina is teamed with teachers and continually provides valuable resources–articles, activities, and how-to videos–to help teachers in their classroom.

Hydrogen Spectrum Activity

Naming the elements, you may also like, dimensional analysis, flame tests and spectroscopy: get excited about color, a model of interacting fields, which chemistry kit is right for you, atomic theory, electron configuration and periodic trends, modeling alpha and beta decay, factors that affect reaction rate, molecular geometry with balloons.

this is an incredible project for the physics course, thank you sharing it

All I needed was the science of popcorn and I run into a grand study of so much more. Thanks for peaking my interest in a few of our universe’s secrets.

Glad you enjoyed this!

Leave a Comment Cancel Reply

Save my name, email, and website in this browser for the next time I comment.

Subscribe to Newsletter

Sign up for free resources delivered to your inbox!

• Biology Topics
• Dissection Resources
• Advanced Placement
• Carolina Correlations
• Carolina 3D
• Video Library

Get Started

• School Year Planning
• Buying Guides
• Carolina Essentials
• Media Center
• Privacy & Security
• 800.334.5551
• [email protected]
• 2700 York Rd, Burlington, NC 27215-3398

August 2, 2024

Origin and Properties of Synthetic and Natural Fibers

December 22, 2023

December 4, 2023

Advantages of Digital Communication Transmission

October 30, 2023

Thermal Convection Currents

The relationship between geoscience processes and mineral distribution, sea floor spreading-divergent plate boundaries.

November 2, 2023

Sparking Curiosity Using Vernier Science Education ® Sensors

March 15, 2024

Data in the Classroom

December 21, 2023

Physical Science Math Review: Techniques, Formulae, and Constants

September 7, 2023

One in a Million: Using Serial Dilutions to…

June 14, 2024

Wisconsin Fast Plants Grower’s Calendar

May 8, 2024

Testing for Segregation of Alleles

April 16, 2024

Introduction to Prokaryotes: Cyanobacteria

April 6, 2024

May 31, 2024

• Lab Material Shopping Lists
• Carolina Lab Skills
• NGSS & 3D Learning
• Workshops & Webinars
• Shop Carolina.com

This website uses cookies to improve your experience. We'll assume you're ok with this, but you can opt-out if you wish. Accept Read More

Remember Me

Forgot Password?

• Free Resources
• Project Search
• Featured Projects
• Member Benefits

1059 Main Avenue, Clifton, NJ 07011

The most valuable resources for teachers and students

(973) 777 - 3113

[email protected]

1059 Main Avenue

Clifton, NJ 07011

07:30 - 19:00

Monday to Friday

123 456 789

[email protected]

Goldsmith Hall

New York, NY 90210

• Why We’re Unique

Introduction: (Initial Observation)

Popcorn or popping corn is a type of maize which puffs up when it is heated in oil or by dry heat. Special varieties of corn are grown to give improved popping yield. Some wild types will pop, but the cultivated strain is Zea mays L . subsp . mays (Everta Group) , which is a special kind of flint corn . It is a popular snack food all over the world.

In the United States, popcorn is particularly common in movie theaters. It is often served with butter and salt. It is also sometimes flavored with sugar (especially in Europe) or spices. In Sweden it is sometimes served with sugar and vinegar.

Popcorn balls (popped kernels stuck together with a sugary “glue”) are a traditional Halloween treat. Cracker Jack is a popular, commercially produced candy that consists of peanuts mixed in with caramel-covered popcorn.

Information Gathering:

Find out about corn and popcorn. Read books, magazines or ask professionals who might know in order to learn about the factors that may affect the ratio of popped kernels in popcorn.

Following are samples of information that you may find:

Popcorn is not a recent food but has been around for thousands of years. It is created by heating corn kernels which explode outwards once the water inside expands and builds up enough pressure. The great thing about popcorn is that it is a good source of carbohydrates, fibre and protein. Slimmers might also like to take note that it is very low in calories (27 calories per 100g) if eaten plain. Want to know more then read on…

Popcorn recipe

25g popping corn Oil 3 tbsp / 40g butter Pinch of salt

Place enough oil into a large heavy based saucepan so that it just covers the bottom. Begin to heat the pan on a medium heat and add the popping corn. Next cover the pan with a tight fitting lid, when the popping starts shake the whole thing vigorously. Once the popping has stopped remove the saucepan from the heat and allow it to cool for a few minutes, this allows any unpopped kernels time to pop.

Melt the butter in a microwave or pan, then gently pour over the freshly popped corn. Stir the popcorn until it is completely coated in the butter, then add salt to taste.

Source…

Question/ Purpose:

What do you want to find out? Write a statement that describes what you want to do. Use your observations and questions to write the statement.

The purpose of this project is to find out:

Which popcorn brand pops faster?

Which popcorn brand pops the most?

Identify Variables:

When you think you know what variables may be involved, think about ways to change one at a time. If you change more than one at a time, you will not know what variable is causing your observation. Sometimes variables are linked and work together to cause something. At first, try to choose variables that you think act independently of each other.

For question “ Which popcorn brand pops faster? ”

The independent variable (also known as manipulated variable) is the brand of popcorn.

The dependent variable (aka responding variable) is the time it takes of popcorn to pop.

For question “Which popcorn brand pops the most?”

The dependent variable (aka responding variable) is the ratio of popped kernels.

Hypothesis:

Based on your gathered information, make an educated guess about what types of things affect the system you are working with. Identifying variables is necessary before you can make a hypothesis.

This is a sample hypothesis:

Among the three brands (HotPop, Critic’s choice and Poppers) HotPop pops faster.

Experiment Design:

Design an experiment to test each hypothesis. Make a step-by-step list of what you will do to answer each question. This list is called an experimental procedure. For an experiment to give answers you can trust, it must have a “control.” A control is an additional experimental trial or run. It is a separate experiment, done exactly like the others. The only difference is that no experimental variables are changed. A control is a neutral “reference point” for comparison that allows you to see what changing a variable does by comparing it to not changing anything. Dependable controls are sometimes very hard to develop. They can be the hardest part of a project. Without a control you cannot be sure that changing the variable causes your observations. A series of experiments that includes a control is called a “controlled experiment.”

Experiment 1: Which popcorn brand pops faster?

Introduction : In preparing popcorn, you heat up the corn kernels in a pot or in a microwave oven. While preparing popcorn you may have noticed that corn kernels do not all pop at the same time. Some pop faster than others. It is possible that some popcorn brands have more of the kernels that pop faster. In this experiment you will compare the popping time among 3 different brands of popcorn.

Safety note: Adult supervision and support is required. You will be working with hot ovens. Let the oven cool off completely between your experiments and before each cleanup. Use of microwave oven is not recommended in this experiment due to a possible risk of causing cancer.

Procedure :

• Get three brands of popcorns.
• Remove 3 kernels of each brand, place them in the center of a 6 x 6 cm aluminum foil (or 3″ x 3″). Add five drops of liquid oil. Three fold the foil and then fold the sides. This will make a temporary small aluminum bag for the seeds. Mark each bag so you will know which bag belongs to which brand.
• Place all bags in an electrical oven.
• Turn on the oven at it’s highest temperature setting and immediately take the time.
• See through the glass window of the oven until the first pocket pops. Immediately record the time and continue your observation until the second foil pops. Record the time again. Continue your observation until the last foil pops and record the time again. (Record time in minutes and seconds past from the time you start the heat. So if you record 5:23 if the sample pops 5 minutes and 23 seconds after you start the heat)
• Repeat this experiment 5 times and record your results in your results table.
• After completion of all five experiments, take an average of the popping time of each brand and record it in the table. Your results table may look like this:

* Note that you may test different brands that are available in your neighborhood.

8. Use the average pooping time to draw a conclusion.

Need a control for your experiment?

You can use a different brand or type of popcorn for your control. Every time that you place one bag of popcorn in the microwave for your experiment, you must place another bag of control popcorn beside that. So for every bag of test popcorn you need one bag of control popcorn. Control can also be another brand of microwave popcorn that you use only as control.

Since always you use the same type of control, the number of popped corns in your controls must remain consistent. If you notice a big change, that might be due to a problem with your microwave device and makes that specific trial invalid. (You need to repeat that).

Many students do not use a control and assume that all experimental popcorns will be tested under identical conditions. Having a control experiment is usually required for higher grades.

Make a graph?

You can use a bar graph to visually present your results. Make one vertical bar for each of the brands you use. The height of the bar will show the average popping time. For example you may use a 75 mm tall bar for a popcorn brand that popped in 75 seconds. Write the brands under or over the bars.

Experiment 2: Which popcorn brand pops the most?

Introduction : In preparing popcorn, you heat up the corn kernels in a pot or in a microwave oven. After preparing popcorn you may have noticed that some corn kernels did not pop at all. Do you know what ratio of the corn kernels did not pop? Is it possible that some popcorn brands have more of the kernels that pop and less of the kernels that do not pop? In this experiment you will compare the popping ratio among 3 different brands of popcorn.

• Get three different brands of microwave popcorn.
• Use the instructions provided with each brand to pop the corn kernels. Stay away from the microwave while it is working.
• When the popcorns are all popped, open each pack and count the number of popped kernels and un-popped kernels. Add them up to calculate the total number of kernels.

5. Calculate the the ratio of popped kernels. To do this you must divide the number of popped kernels by the total number of kernels. 6. Report the ratio of popped kernels in each brand and conclude which popcorn brand has the highest ratio of popped kernels.

Materials and Equipment:

• Toaster oven
• Microwave oven
• Aluminum foil
• Three different brand of popcorn

Results of Experiment (Observation):

Experiments are often done in series. A series of experiments can be done by changing one variable a different amount each time. A series of experiments is made up of separate experimental “runs.” During each run you make a measurement of how much the variable affected the system under study. For each run, a different amount of change in the variable is used. This produces a different amount of response in the system. You measure this response, or record data, in a table for this purpose. This is considered “raw data” since it has not been processed or interpreted yet. When raw data gets processed mathematically, for example, it becomes results.

Calculations:

To calculate the total number of kernels you must add the number of popped kernels to the number of un-popped kernels.

To calculate the ratio of un-popped kernels you must divide the number of un-popped kernels by the total number of kernels.

Summary of Results:

Summarize what happened. This can be in the form of a table of processed numerical data, or graphs. It could also be a written statement of what occurred during experiments.

It is from calculations using recorded data that tables and graphs are made. Studying tables and graphs, we can see trends that tell us how different variables cause our observations. Based on these trends, we can draw conclusions about the system under study. These conclusions help us confirm or deny our original hypothesis. Often, mathematical equations can be made from graphs. These equations allow us to predict how a change will affect the system without the need to do additional experiments. Advanced levels of experimental science rely heavily on graphical and mathematical analysis of data. At this level, science becomes even more interesting and powerful.

Conclusion:

Using the trends in your experimental data and your experimental observations, try to answer your original questions. Is your hypothesis correct? Now is the time to pull together what happened, and assess the experiments you did.

Related Questions & Answers:

What you have learned may allow you to answer other questions. Many questions are related. Several new questions may have occurred to you while doing experiments. You may now be able to understand or verify things that you discovered when gathering information for the project. Questions lead to more questions, which lead to additional hypothesis that need to be tested.

Possible Errors:

If you did not observe anything different than what happened with your control, the variable you changed may not affect the system you are investigating. If you did not observe a consistent, reproducible trend in your series of experimental runs there may be experimental errors affecting your results. The first thing to check is how you are making your measurements. Is the measurement method questionable or unreliable? Maybe you are reading a scale incorrectly, or maybe the measuring instrument is working erratically.

If you determine that experimental errors are influencing your results, carefully rethink the design of your experiments. Review each step of the procedure to find sources of potential errors. If possible, have a scientist review the procedure with you. Sometimes the designer of an experiment can miss the obvious.

References:

List of References

Popcorn.org

Popcorn history

Early popcorn history

It is always important for students, parents and teachers to know a good source for science related equipment and supplies they need for their science activities. Please note that many online stores for science supplies are managed by MiniScience.

Testimonials

" I called School Time and my husband and son came with me for the tour. We felt the magic immediately."

- Robby Robinson

" My husband and son came with me for the tour. We felt the magic immediately."

- Zoe Ranson

Contact Info

Our address, working hours.

Week Days: 07:00-19:00

Saturday: 09:00-15:00

Sunday: Closed

Science Project

Scientists Discover the Secret of Popcorn's Popability

Yes, those unpopped kernels of corn can break a tooth. But for most of us, they're just an annoying disappointment as the edible bits dwindle before the movie is over.

Not all corn pops well. A new study found that out of 14 varieties of popcorn, the number of unpopped kernels ranged from 4 percent to a staggering 47 percent.

More important, the study may reveal how to make better popcorn.

"We think the secret to maximizing 'pop-ability' is found in the special chemistry of the corn kernel," says Bruce Hamaker, a food chemist at Purdue University. "We now have a better understanding of the science behind why unpopped kernels occur and how we can use this knowledge to go about reducing their number."

Big business

This is obviously an important pursuit. Americans consume 17 billion quarts of popped popcorn every year, according to an industry group called the Popcorn Board. That's 54 quarts per man, woman and child.

American farmers produce more than 300 million tons of corn a year, nearly half the world's production.

Sign up for the Live Science daily newsletter now

Get the world’s most fascinating discoveries delivered straight to your inbox.

Orville Redenbacher, Paul Newman and the others who sell popcorn seek corn known to pop well. The industry sometimes claims 98 percent popability. Feel free to test that claim at home.

Hamaker's team has uncovered the crystalline structure in popcorn that appears to govern whether it pops or not.

The key seems to be the varying chemical structure of the outer hull. As the kernels heat up, the hull acts like a pressure cooker to lock moisture inside. Pressure builds until the kernel ruptures, turning it inside out.

Good poppers have a stronger hull with a highly ordered crystalline structure, the investigation found.

Coming to your microwave

Hamaker and his colleagues say future research should be able to determine how to transfer the best hull properties to other corn kernels, perhaps through selective breeding, genetic engineering, or even by simply adding chemicals to modify the hulls.

Improved microwave popcorn could be on grocery shelves within five years, Hamaker said.

The study, funded by Purdue, will be published July 11 in the American Chemical Society's journal BioMacromolecules .

• Engineering OJ: Terrible Smells Make Juice Fresh
• Food, Drugs, or Designer Shoes: Mind Treats All Cravings Equal
• High-Tech Kernel of an Idea

Robert is an independent health and science journalist and writer based in Phoenix, Arizona. He is a former editor-in-chief of Live Science with over 20 years of experience as a reporter and editor. He has worked on websites such as Space.com and Tom's Guide, and is a contributor on Medium , covering how we age and how to optimize the mind and body through time. He has a journalism degree from Humboldt State University in California.

What are ultraprocessed foods?

Does fake meat cause heart disease? Here's what the science actually says.

1st map of Antarctica's green space unveiled. Here's what it shows.

Most Popular

• 2 No, NASA hasn't warned of an impending asteroid strike in 2038. Here's what really happened.
• 3 Milky Way's black hole 'exhaust vent' discovered in eerie X-ray observations
• 4 NASA offers SpaceX $843 million to destroy the International Space Station
• 5 Which continent has the most animal species?
• 2 This robot could leap higher than the Statue of Liberty — if we ever build it properly
• 3 Zany polar bears and a '3-headed' giraffe star in Nikon Comedy Wildlife Awards
• 4 Which continent has the most animal species?
• 5 Newly discovered asteroid larger than the Great Pyramid of Giza will zoom between Earth and the moon on Saturday

• Benefits to Participating Communities
• Participating School Districts
• Evaluations and Results
• Recognition Accorded
• National Advisory Committee
• Establishing New Institutes
• Topical Index of Curriculum Units
• View Topical Index of Curriculum Units
• Search Curricular Resources
• View Volumes of Curriculum Units from National Seminars
• Find Curriculum Units Written in Seminars Led by Yale Faculty
• Find Curriculum Units Written by Teachers in National Seminars
• Browse Curriculum Units Developed in Teachers Institutes
• On Common Ground
• Reports and Evaluations
• Articles and Essays
• Documentation
• Video Programs

Have a suggestion to improve this page?

To leave a general comment about our Web site, please click here

Share this page with your network.

Being Corny: Using Popcorn to Explore Thermodynamics

Introduction.

Popcorn. Depending on your age, different images spring to mind. Maybe it’s a buttery bucket dancing across a drive-in theater screen or the magical Jiffy Pop commercial from the 1970s. For most students today, if it is made at home, it comes in a microwaveable bag, usually pre-seasoned. Americans eat 90% of all the popcorn produced in this country, yet very few ever stop to think about what makes popcorn pop.

As noted French anthropologist Claude Levi-Strauss once said, “the scientific mind does not so much provide the right answers as ask the right questions.” As teachers, when we present students with a phenomenon, our goal should not be to have students give us a single textbook answer. Instead, what we really want is for them to generate a series of questions. It is from their own attempts to answer those questions that they will come to make sense of the world around them. In this unit, my goal is to demonstrate how investigating what makes popcorn pop can lead to a better understanding of thermodynamics and molecular interactions at the middle school level.

I am currently a sixth grade science teacher at Henry B. DuPont Middle School, a comprehensive public middle school in the Red Clay School District. It has approximately nine hundred students distributed over the sixth through eighth grade band. H. B. is located in a suburban setting but draws from both the city of Wilmington and the suburbs of Hockessin and Newark with a present composition of forty percent city and sixty percent suburban. Our feeder pattern consists of eight different elementary schools. There is a great disparity between the urban and suburban students on average when it comes to academic readiness and diversity of background knowledge. It is not a matter of potential ability but previous opportunities and, in some cases, differing expectations. The academic range in science has further been extended by increasing the amount of inclusion.

Delaware’s science curriculum is in a transition phase which allows me some freedom to create learning opportunities that align to the Next Generation Science Standards (NGSS), even if they don’t align to the current grade level curriculum map. The aim of the three stranded approach of the NGSS is to more fully engage students in critically using science rather than memorizing facts. At the same time, science should be for all, including those that struggle with literacy. My job is to design experiences and share visual representations that will help students discover and understand key ideas relating to temperature and change of state in some cases with minimal reliance on text support.

This particular unit is designed to meet both the NGSS and a wide range of students’ abilities and backgrounds. Students will use science and engineering practices to answer a question of their own choosing while incorporating Common Core math and language standards. Although I will be implementing it in sixth grade, it could be used across the middle school grade bands.

The unit is divided into three parts. It will start with the phenomenon of popping corn. Students are provided with a variety of resources to build background knowledge. Then students will look at the thermodynamics of heat transfer as it relates to phase changes using water. Lastly, they will design, execute, and analyze their own experiments connected in some way to popcorn. Depending on readiness, students may do additional research on the structure of saturated and unsaturated fatty acids as it relates to both oils used in preparation and in flavoring.

As stated earlier, this unit serves as a bridge. In the Science Education for Public Understanding Program unit “Studying People Scientifically , ” students learn about some aspects of investigation protocol such as the use of a control, multiple trials, sample size and data analysis. They learn about qualitative and quantitative data and how each type provides information. “Being Corny” increases the rigor by requiring the students to generate the questions, hypotheses, and procedures. The properties of water and its changes of state provide a link to the Earth History unit that follows. Whether as a source of weathering (frost wedging), erosion (glaciers, running water), or transpiration and evaporation, water’s changing states affect the Earth’s surface. Lastly, the concept of transformation of energy and energy and motion relate to the current Forces and Motion unit.

There are several key science concepts that students will explore through the phenomenon of making popcorn. At the simplest level, they will discover that it is the structure and the percentage of water in the kernel of popcorn which allows the pressure of the water vapor to build until the hull bursts. Students will connect Gay-Lussac’s Law, which describes the relationship between pressure and temperature, given a constant volume of a gas to the pressure change inside the kernel. This change of state of the water is due to the change in the arrangement and movement of the molecules as a result of having energy added in the form of heat. Furthermore, there are different ways for electrical energy to be converted to heat energy which in turn affects how efficiently corn pops. On a more general level, students will discover that matter has different properties depending on whether it is in a solid, liquid, or gas phase. They will connect changes of temperature with the changing motion of molecules and how that relates to density. Lastly, they will see how the molecular structure of a substance determines its properties.

Content 

Laws of thermodynamics.

Zeroth Law states that if two thermodynamic systems are each in thermal equilibrium with a third, then they are in equilibrium with each other. Putting it in algebraic terms, if A = C and B = C, then A = B. The First Law of Thermodynamics is that energy can neither be created nor destroyed. It can only change forms. In other words, the net heat given to a system equals the net work done by the system. The Second Law of Thermodynamics states that heat energy moves from less structure to more structure. In other words, heat will always be transferred from a higher source which is hotter and more disorganized to a lower one which is colder and more organized, until the two are in equilibrium. The Third Law of Thermodynamics is that as temperature approaches absolute zero, the disorder and randomness of a system approaches a constant minimum. In other words, at absolute zero, molecular movement is almost fixed in time and space.

Types of Heat Energy

Conduction is heat energy transferred from one thing to another through direct contact. Convection is heat energy transferred through indirect contact, for example through the flow of air or water. Radiation is heat energy transferred from one object to another through space by electromagnetic radiation.

Phases of Matter

There are five main phases of matter: solid, liquid, gas, plasma, and Bose-Einstein Condensates. For the purpose of this unit, I will focus on the first three. The main difference in the structures of each state is in the densities of the particles. In the solid phase, matter has a definite shape and volume. The particles that make it up, either atoms or molecules, are joined together by strong bonds which give it a fairly tight structure. Sometimes the bond arrangements create a repeating pattern known as a crystal lattice. Quartz, granulated sugar, table salt, and ice all display a crystal lattice pattern. From the outside, solids look static but inside, the molecules continue to vibrate but stay in place relative to each other. In some cases, like water, volume may be larger in the solid state than the liquid state due to the arrangement of the molecules. Matter in a liquid phase has a definite volume but no definite shape. The bonds are weaker than in the solid phase and the particles are able to move further apart. While volume remains constant, liquids take on the shape of their container. In the gas phase, matter has neither shape nor volume. The forces attracting the particles are so weak that the atoms and molecules can spread out to fill the available space.

Elements and compounds can move from one state to another when specific physical conditions change. A sufficient change in energy and/or pressure can cause a phase change. Most elementary students are familiar with “melting” and “boiling” to describe the state changes from a solid to a liquid and a liquid to a gas, respectively, as they are things they experience in their everyday lives; ice melts and water boils. They may also know “freezing” and “condensing,” liquid to solid and gas to liquid, from learning about the weather or the water cycle. Most, however, do not know that “sublimation” describes going from a solid phase to a gas phase, as in dry ice. When demonstrating sublimation with dry ice, I also discuss condensation because carbon dioxide gas is colorless and odorless.  The smoke that students see is the water vapor in the air changing state from a gas to a liquid as the heat is transferred to the colder carbon dioxide gas.

The easiest way to add energy is to add heat. The more energy the atoms and molecules have, the more they move. When a substance transfers its heat, it loses energy and the particles move closer together. A second way to cause a phase change is to increase pressure. Examining the ideal gas law will help us to understand the relationship between pressure, volume, and temperature. The kinetic theory states that all gases are made up of very small particles with no forces of attraction or repulsion between them. These particles move randomly, independently, in straight lines until colliding with the walls of their container or each other, which causes them to mix uniformly. The temperature of the gas reflects the average kinetic energy of the gas particles. When looking at the mechanism of popping corn, the two most important variables are pressure and temperature. Since the water is contained within the pericarp, the popcorn hull, volume is constant. Gay-Lussac’s Law states that the pressure of a given amount of gas held at constant volume is directly proportional to the Temperature in Kelvin units. As temperature rises, the pressure of the gas, water vapor, rises. 1

The Kelvin scale is the logical extension of the relationship between temperature and volume. At absolute zero, theoretically there is no molecular movement. Each unit on the Kelvin scale equals one degree on the Celsius scale. Although my students will use the Celsius scale for collecting and analyzing data, I will give them the conversion formulas:  F = C x 9/5 + 32 and C = (F – 32) x 5/9

What makes popcorn pop? The short answer is water found inside the kernel. Yet science is as much, if not more, about the questions rather than just the answers. Lots of foods have water inside them, but they don’t pop in the microwave. Or do they? Consider a watermelon; it has so much water that it is even part of the fruit’s name, yet we don’t put it in the microwave. Maybe it’s a question of seeds. We don’t expect the fruit to pop; however, neither do the watermelon seeds. In fact, there are very few seeds that meet the structural conditions needed to pop; amaranth is one, but none of them do it as well as popcorn.

History of Popcorn

Who invented this culinary marvel? Archeological evidence suggests that popcorn is a naturally-occurring variety of corn. In the 1940s, the Rockefeller Foundation, in conjunction with the Mexican Ministry of Agriculture, collected more than 2000 varieties of corn, maize , from Mexico. Among those listed were four “ancient indigenous” races of corn: Palomero Toloqueno, Arrocillo Amarillo, Chapalote, and Nal-Tel based on ear and kernel characteristics. Like modern popcorn varieties, all four have pine cone shaped ears and small dense kernels. Archeological findings support their claim of antiquity. Brown Kernels about 4000 years old related to Chapalote were discovered in the Bat Cave of New Mexico. In La Perra Cave, in northeastern Mexico, 2000 year old cobs related to Nal-Tel were found. 2  

There are five main types of corn: flint, sweet, dent, flour, and popcorn. Flint corn ( Zea mays indurata ) has kernels with hard outer shells and can range in color from white to red. This is the type associated with ornamental corn. It can also be used as animal feed. Central and South America are the largest growers of flint corn today. Sweet corn ( Zea saccharata or Zea rugosa ) is the type most eaten by people, either fresh on the cob or processed as a frozen or canned food. It gets its name because it has more natural sugars than other types of corn at the same developmental stages, 10% for sweet corn compared to 4% for field corn. However, once picked, the sugars begin converting to starch, losing up to 50% of its sweetness after one day. Dent corn ( Zea mays indenata ) is also known as field corn. It gets its name from the indentations on the kernels at maturity. It can be white or yellow, contains both hard and soft starches and is usually used as animal feed, in processed foods and in various industrial products including ethanol. The fourth type’s name flour ( Zea mays amylacea ) explains its use. It has a soft, starch filled kernel, that easily grinds down to produce the starch flour that is used in many different food preparations. In addition to supplying nutrition, starch is what gives cooked food its shape. It is usually white but can also be other colors as in blue corn tortilla chips. Flour corn is one of the oldest cultivated types and the one mostly grown by Native Americans. Last, but certainly not least, is popcorn ( Zea mays everta ). Popcorn is related to flint corn in that it has a hard exterior shell, known as the pericarp. Inside is a soft endosperm and water. 3  

Agronomists classify the popcorn endosperm as everta because it turns inside out, or everts, when heated. The water inside the kernel is changed to steam. The increased pressure causes the pericarp to split and the starchy endosperm flakes producing the treat we call popcorn. In other types of corn, either the steam escapes gradually or the kernel splits without exploding.

That the everta class has remained distinct over so many centuries is due to a quirk in its genetics. Although its pollen can fertilize other types of corn, most but not all evertas have a gene, Gametophyte Factor I, that inhibits it from being pollinated by other types of corn. The gene comes in 2 forms, Gal-M gene slows down the pollination by other species, allowing time for everta pollen to sneak in and do the job. Gal-S gene is even more effective by completely blocking other varietal pollen.

Breeders use this one-way flow of genetic information by breeding their everta with purple dent corn. If the resulting ears have the purplish tinge then the everta lack the desired gene. If, however, the pigment is missing, then the trait is there. This test allows organic seed corn producers to exclude genetically modified pollen from dent and sweet corn types. As of this writing, although many other varieties of corn have been genetically modified to be more drought and disease resistant, the popcorn variety of corn has not. 4

Physical Description

A popcorn kernel has three important parts: the pericarp, also known as the seed coat or hull, the endosperm, and the embryo. The pericarp provides protection for the endosperm and embryo. In the case of popcorn, damage to the pericarp can mean a loss of water and less popping. The endosperm fills most of the kernel and is the main energy source for the developing seedling. The embryo contains the miniature plant. It also contains a cotyledon, which provides energy for germination. 5 Popping corn kernels have a dense, hard translucent endosperm with a tiny bit of soft endosperm next to the embryo.  Of all the grain corns, popcorn types have the smallest kernels, appearing as either pearl type or rice type. Pearl have a rounded top whereas rice come to a point. Some varieties may produce ears with both types but a single ear is always homogenous. There are anywhere from 14 to 28 rows of kernels on a cob and they appear in a variety of colors. The color of the kernels has no effect on the color of the popcorn as it is the white endosperm that explodes. So, while the gourmet colored popcorn will look prettier than its plain golden yellow cousin when displayed in the glass jar on the counter, there will be no color difference in appearance when popped. When fully dry, the kernels and pedicel, the portion of the pericarp attached to the cob, easily detach but the brittle nature of the kernels make gentle handling a must. Kernels with damaged pericarps will not pop as well because the steam inside will escape through the cracks before building up enough pressure to cause the endosperm to explode. 6

Modern Cultivation

Commercial popcorn cultivation has existed in the United States for more than 150 years. In 1865, Fearing Burr (a noted seeds man) listed 5 “parching corn” varieties available: two with white kernels, two with yellow and a red rice type. As of 2011, the Seed Savers Exchange inventory listed 31 varieties of popcorn. Commercial popcorn today is bred for their flake types and popping expansion. The more the starchy endosperm expands, the softer the piece. There are two types of flakes: “Butterfly” and “Mushroom.” Butterfly popped kernels are more angular, softer and are generally the shape most associated with the popcorn made at home and eaten in theaters. Mushroom type is compact and more rounded. Since it has less breakage, it is better suited for being kettle flavored i.e. caramel corn. Mass producers tend to favor hybrids that produce a bland neutral flavor so as not to interfere with the added flavorings. 7

Recently, there seems to be a resurgence in interest in heirloom varieties and a backlash against the hybrids. In the New York Times article “Heirloom Popcorn Helps a Snack Reinvent Itself,” 8 Kim Severson suggests that this may be the latest example of popcorn’s renaissance. In the 1880s, steam popping machines brought the treat from the farm kitchen to the cities. It was an integral part of movie escapism in the Great Depression. Jiffy Pop, with its ease of preparation, brought new life to the snack in the late 1960s after television replaced going to the movies. The nature of the popping mechanism and the way that a microwave works were a perfect match. Most microwave ovens still have a popcorn setting. A walk through the supermarket aisle reveals at least a dozen different brands and types of microwave popcorn. Yet even as the popularity seemed to be increasing, there were a few people wanting something different: a popcorn whose taste comes from the seed without any added oils, butters, flavorings, or salts. Gene Mealhow, farmer and owner of “Tiny but Mighty” heirloom popcorn, blames Orville Redenbacher for the change in emphasis from taste to size. Redenbacher, a 1928 graduate of Purdue University, used genetic material developed through his university’s alumni seed improvement association to create a hybrid seed that produces bigger kernels with a higher popping rate—all at the cost of taste. According to Mealhow, “Orville produced a giant popcorn to be a delivery vehicle for butter and salt.” 9

As part of developing this unit, I obtained several different types of popcorn kernels to see for myself what, if any, differences existed. I won’t influence the reader by sharing my opinions, but the experience did affect my planned teaching of this unit.

Globally, the United States is the largest producer of popcorn, but we consume 90% of it almost exclusively as snack food. This leaves only 10% for export. Argentina ranks second in production, though their yield is approximately half of the U.S. total. Their domestic use is much lower, being largely limited to public places like movie theaters and bars but little home consumption. As a result, they export 95% of their yield, making them the largest exporter of un-popped corn in the world. 10

Ways to “Heat” Popcorn: Historical to Present

If we had a time machine, we’d probably discover that the first instances of “popping” corn were accidental. Tomie DePaoli’s Popcorn Book , an almost mandatory elementary school read around Thanksgiving, states that Native Americans used to throw kernels directly into a fire and then try to catch the morsels as they popped and flew back out. While it seems fanciful, scientifically it is possible. However, De Paoli also depicts popcorn as being served at the First Thanksgiving. 11 According to Stephanie Butler, writer for the History Channel, there are no contemporary accounts that reference popcorn. What she does verify is that in 1612, French explorers saw some Iroquois women popping corn in clay pots. They would fill the pots with hot sand, then add the kernels before stirring it with a stick. When the corn popped, it came to the top of the sand. 12 Holding the dried ear of corn over a fire is another method presented by de Paola and verified by National Geographic . 13 However, I wasn’t able to verify tossing the kernels directly into the flames as a cooking method.

Until the invention of the microwave, all methods of popping corn were basically the same. Heat was applied to the outside of the popcorn kernel, either directly or through oil. That heat energy was then conducted through the pericarp, the hull, and transferred to the starchy endosperm and water found inside the seed. Two physical changes occur. The endosperm becomes a gelatinous starch that solidifies when released. The water molecules go through a change of state from a liquid to a gas. When the pressure of the water vapor exceeds the internal strength of the pericarp, the kernel breaks open, turning itself inside out in the process with the starchy endosperm now the fluffy outside and the brittle pericarp reduced to almost nothing.

The first widely successful commercial poppers appeared in the United States in the late 1800s. Just as Edison is associated with the light bulb, Charles Cretors was the man for roasting and popping machines. He wasn’t an engineer but a shopkeeper who sold candy. Disappointed with a peanut roaster he’d purchased, he decided to make a few adjustments. He was so successful that one of his providers decided to sell his improved version, thus starting C. Cretors and Company, which continues to make popcorn poppers today largely for commercial venues. The history of popcorn machines is fascinating and there are even two museums devoted to them: J.H. Fentress Antique Popcorn Machine Museum in Holland, Ohio and the Wyandot Popcorn Museum in Marion, Ohio. 14 A common element of most of the early machines was the use of oil to enhance the flavor and the aroma and it is still the method used most often today in non-microwave popping.

Contemporary non-commercial popcorn poppers fall into two main types: those that use air and those that use an “arm” to move the kernels along and away from the heated surfaces. Rather than discuss both, I want to focus on the air popper as it generates the most student misconceptions. The name is misleading as it gives the impression that the popping comes from heating the air rather than the kernel. Like other stand-alone electric poppers, the kernels are heated by coming in contact with a metal plate, either directly or through the heated oil. Under the plate is a heating element which is connected to both a thermostat and a thermal fuse. The thermostat consists of two different metal arms that react differently to changing temperatures. As the thermostat gets heated, one arm will expand and break the circuit as it bends away from the other. As it cools, it returns to position and current can flow again. It’s what helps regulate the temperature for optimum popping. The thermal fuse is a safety feature. In case of dangerous overheating, it melts and the circuit is permanently broken until a replacement piece can be installed. The purpose of the air is to move the popped kernels away from the heat source. Since they have greater surface area, they are lifted out of the way, making room for the un-popped kernels. This is done with a small fan powered by a direct current motor. Four diodes, placed on the circuit board, keep the current moving in only one direction, in effect, turning the alternating current from the wall to the direct current needed to power the motor. As the motor spins, it turns a small plastic disc with fan blades molded into it. The air then escapes from slots in the heating element portion. 15  In a rotating “arm” model, the oil, if used, heats up first and then the heat energy is transferred, conducted, to the popcorn seed. The arm helps to insure more even heat by turning the kernel over and moving the lighter popped pieces out of the way of the heavier un-popped kernels.

Microwave energy works completely different. Instead of the heat being applied externally, the rays directly excite the water molecules inside the pericarp. Popcorn played an important role in the development of the microwave oven as a cooking device. The first patent for microwave popcorn actually belongs to a company that provided magnetron tubes, an essential part of the radar systems used in World War II. The story goes that one day, Percy Spencer, a scientist at Raytheon, was experimenting with magnetrons in his lab, looking for new uses. He noticed that the candy bar in his pocket had melted and wondered if it was due to the device. He sent out for popcorn kernels, put them in a paper bag and held them next to a magnetron. Voila! Popcorn. Spencer then built a rudimentary metal box with a magnetron in it, creating the first microwave oven. After researching further and conducting more experiments, Percy Spencer filed for and successfully received a patent in 1945. For his invention, Spencer received no royalties, but he was paid a one-time, two-dollar gratuity from Raytheon—the same token payment the company made to all inventors on its payroll at that time for company patents. 16 Before you think bad of Raytheon, it was and still is the way things work in industry. As a research scientist with Hercules, my father developed many innovative processes and was paid the same two dollars for each time he had his name on the patent.

In 1954, Raytheon produced the first commercially built microwave oven which was a little under six feet tall and weighed around seven hundred and fifty pounds. It cost between two and three thousand dollars and was initially used in restaurants, railways and ships as they were too bulky and expensive for home use. It also had some shortcomings; for instance, meat, while it cooked, wouldn’t brown, and not all things heated evenly. After further research and modification in design, the first microwave oven for home use was put on the market by Amana, a Raytheon subsidiary, under the name “RadarRange” in 1967. It could be had for around five hundred dollars and fit on a kitchen counter. 17

As I researched the origin of the microwave oven, I was taken back in time to Christmas of 1971. There was a large wrapped box sitting in the dining room addressed to my mother from my father. For weeks, she had tried to guess its contents: sheets and towels, clothes, a whole lot of smaller boxes inside one big box. Each time, my dad only smiled and said no.  He was definitely more excited than she was when the gift was finally opened: a brand new microwave oven! I can still remember the first thing we made in it, cups of water for either tea or hot chocolate. Yes, we could have used a tea kettle, and usually did, both before and after, but this was a new way of cooking.

I’ll confess that up until designing this unit, the microwave oven had remained a magic box to me. So how exactly does a microwave oven work? It all starts with electricity, a transformer and a magnetron. The alternating current from the wall needs to be transformed to a high voltage direct current of 2000-3000 volts which is the job of the transformer. This current is then sent to the Magnetron, which is a kind of vacuum tube. Before there were transistors, many electronic devices had tubes. They are made of glass with a filament that allows for a controlled flow of electrons. Inside the magnetron, voltage is applied to a filament sending a stream of electrons down the inside of the metal tube. As the electrons move, circular magnets cause them to spiral. The spiraling beam passes by holes in the side of the tube which causes high frequency radiation to be emitted from the end of the tube. This radiation has a wavelength of about 12 cm, 5 inches, and can pass through glass and transparent plastic, which is why glass lids aren’t a problem. The radiation, however, doesn’t pass through food but is absorbed by it, causing the food molecules to vibrate. They vibrate because they are not symmetric which produces a positive and a negative end, which aligns with the electric field. Since the electric field created by the microwaves is constantly changing, so are the food molecules. Think of it as watching a magnet flip over and over, as a stronger magnet’s pole orientations keep shifting. The back and forth motion creates the heat that cooks the food. To help things cook more evenly, many microwave ovens have a fan that interrupts the flow of radiation to spread it more throughout the cooking chamber. 18  

That explanation helped a little in identifying the hidden parts of the microwave oven, but I still struggled with the science part of it. I readily tell my students that I don’t have all, or even most, of the answers, but my own observations of how different foods heated told me that I was missing something important in the way microwave ovens work. I also needed to clarify what electromagnetic radiation was and how microwaves were different than other forms of radiation. Electromagnetic radiation are waves of pure energy that travel through space at the speed of light. The properties of electromagnetic radiation waves are determined by their specific wavelength and energy. It is an inverse relationship; the shorter the wavelength, the greater the energy. When comparing the potential cooking power of two microwave ovens, one needs to consider both the power output, which is usually between six hundred and nine hundred watts and the size of the cooking space. Magnetron power is a measure of watts produced not the amount of electricity used. To compare efficiencies, you need to divide power by cubic feet. 19

So why doesn’t all food heat up the same? The answer is water content, or something else that is hydrophilic, attracted to water and also polarized. The molecular structure of water is a dipole, which means that it lines up with an electric field, like a compass. The microwaves produce an electric field that shifts polarity almost five billion times per second. Likewise, the individual water molecules shift their orientations. This causes them to bang against each other and gain speed. Faster moving molecules mean hotter molecules. Although they have a lot of energy, microwaves don’t penetrate very far which is why there are two other heating mechanisms occurring. Think back to popping corn. Even though there are recommended times, we use our ears to decide when we should stop the cooking.

The radiation causes the water molecules in the food to heat up. Even before they pop, kernels get warm. This warmth is then conducted to the adjacent less hot molecules; The Second law of Thermodynamics in action. At the same time, the water is being turned into steam. In most cases, the water vapor goes through the rest of the food, transferring its heat. In the case of popcorn, the steam builds up inside the pericarp until the internal pressure exceeds the hull capacity, approximately 135 psi, pounds per square inch. At that point, the hull ruptures, releasing both the steam and the starchy endosperm. The steam now acts as convection heat so that the remaining kernels are being heated from within and without. After the initial few pop, we hear most of the rest pop shortly after. When popping slows down, it is because the bulk of the steam energy has been used. A way to demonstrate this is to pop popcorn in a microwave safe container with a lid and without. Since we know that the waves can penetrate glass, any difference in efficiency will be due to the steam and not the microwaves.

As Spencer had demonstrated back in 1945, microwave energy could be used to cook popcorn but it would require a change in the food packaging to increase its popularity. The first patent for a microwave popcorn bag was issued to General Mills in 1981, and home popcorn consumption increased by tens of thousands of pounds in the years following. 20 The modern microwave popcorn bag was actually the center of a very big lawsuit between Hunt Wesson, Orville Redenbacher brand, and General Mills, Act 11 brand. While it is possible to use a plain folded paper bag to hold the kernels, companies soon saw the added value of creating a better vessel. People loved the convenience of Jiffy Pop as it contained the oil, popcorn, and seasonings all in one. What if the same could be done with a coated bag that could be used in a microwave oven? Act 1 popcorn went so far as to use real butter, oil and salt but that required refrigeration. Act 11 solves the problem by using synthetics. Adding flavoring agents also meant coating the inside of the bags. Flavor was better but there were still too many un-popped kernels. What was needed was a way to distribute the heat more evenly. Although microwave ovens operate at higher efficiency ratings and can cook food quicker, the nature of the heat means that the waves are not always evenly distributed. To get that effect, you need a material that absorbs a small portion of the radiation and converts it to heat. 21 Metal, used correctly, can do that job. If it is too thin, it overheats and melts. If it has sharp points, it can cause sparks. The metal threads now found in most microwave popcorn bags, have been designed to avoid both issues while still providing a conduction heat source. As a result, the modern microwave popcorn bag utilizes all three times of heat: radiation from the magnetron, conduction from the bottom of the bag and convection from the steam released by the bursting pericarps. Evidence of the latter two can be found in heat outside the “floor” of the bag, the inflation of the bag during cooking and the release of steam when opened carefully.

Teaching Strategies

Instruction will incorporate the following eight Science and Engineering Practices. Students will obtain, evaluate, and communicate information as they use multimedia to build background knowledge and answer the question of what makes popcorn pop. They will use mathematics and computational thinking as they conduct an investigation looking at water content and popcorn volume, kernel size, and percentage of popped kernels. They will develop and use models to show the molecular structure of water and its polarity. They will create density models to show change of phase and use technology as they collect and graph temperature/time data. Defining problems and designing solutions will be used as students strive to create insulators for ice cubes with the goal of keeping them from melting the longest. Lastly, they will plan and carry out an investigation of their own choosing in some way connected to popcorn, analyzing and interpreting their data before engaging in argument with evidence. Specific strategies chosen to best meet the needs of this age group and diverse population include flexible grouping depending on the nature of the activity, rotating roles and responsibilities, encouraging participation and building vocabulary and content knowledge through think, talk, write, pair, share, modify writing. The emphasis will be on formative assessment using focus questions and providing multiple pathways to demonstrate knowledge for summative assessments. The three strands of the Next Generation Science Standards (NGSS) will be the basis of creating assessments that incorporate the cross cutting concepts and science and engineering practices along with the disciplinary core ideas on matter and its interactions.

Student Activities Popcorn Science

Phenomena-Popcorn

Day 1 Activating Prior Knowledge

Warm up activity: Supply each student with a piece of 8 1/2 by 11 inch scrap paper, blank on one side. On it, have them label three columns: know, sense data, questions, but instruct them not to put their names on the paper. Give students 3 minutes to write down as much as they can in the know column about popcorn and any questions that they might have in the third column. For the students who respond “I don’t know anything” or “I don’t have any questions” prompt them by asking them to think back on the last time they either ate or saw popcorn. Then show a clip of an old style popcorn ad either from a drive-in, movie theater, or school house rock.

Then teacher makes the popcorn using a non-microwave method. Depending on resources available it could be a stand-alone popper, either oil or air, jiffy pop over a hot plate, a regular lidded pan with kernels over a hot plate or the specialized cookware needed with an induction burner. Most students have only had popcorn at the movies or from a microwave so they will be interested in the cooking as well as the prospect of eating. As the process occurs, ask students to note what they see, hear, or smell as well as any additional questions that come to mind. Give two minutes at the end for students to add to notes. Then have students do a “popcorn” share. Each student crumples up his/her paper, form a circle and then “pop” the corn by tossing papers in the air into the center of circle. Repeat 2 times and then have students open up and share what is on the paper in front of them. While passing out the popcorn, have students write any questions from the claimed paper on a sticky note and add to a class chart. Show students the short video of the popcorn expanding and then ask them to explain the phenomena. Use I think, he thinks, we think strategy where each student writes their explanation; then students partner up and restate their partner’s explanation; then they come up with one explanation to present to the group.

Day 2 and 3 Investigating the Influence of Water on Popping Rate

Warm up activity: Have students discuss ways with their shoulder partners to prove that the amount of water inside the pericarp affects how the popcorn pops. Through Socratic questioning techniques, lead them into the following experiment. Working in teacher-selected heterogeneous groups of three to four students with clearly defined roles, students will carry out the following experiment. Students will count out 6 bags of 50 kernels each of the same type of un-popped corn. They will weigh and record the starting weights of each bag. Three of the bags will be the controls, three of the bags will have 20 ml of water added, and three will have their contents removed, put in a 200 degree oven for an hour, allowed to cool and then replaced in the bag. On day 2, students will reweigh each of the three bags, after pouring off and measuring any remaining water. There should be a difference in weight. The soaked seeds should weigh more, the dried seeds less and the control should be the same. Students will then try to pop each of the six batches using the same method. They are collecting three pieces of data for each sample: the percentage popped, the average kernel size (measure a random line of 10 using centimeters, then divide) and the total popped volume. Depending on the readiness of the students, different averages could be considered. It would make sense to use the mean for volume and length as both can be fractional parts whereas it doesn’t make sense to use it for number/percentage popped. Students could also use the median for all three. Again depending on the readiness of the students, students could create bar graphs for each category. More mathematically advanced students could create box and whisker plots which will show how reliable the data are.

Day 4: Claim, Evidence, Reasoning Literature/Experiment Connection

Students will read the New York Times article 22 and evaluate for bias. They will then take part in a double blind teacher designed experiment to evaluate claims from within the article. Students will collect qualitative data in the form of taste preference and quantitative data in the form of volume, popped kernel size, and percentage of kernels popped. They will then write a persuasive essay either supporting or refuting the content of the article using experimental evidence.

Days 5-14 Investigating Water and Change of State

In this middle part of the unit, the focus switches from popcorn and the change of state of the water in the kernel to a much broader look at the relationship between energy, temperature and change of state, using water as the medium.

Water Investigations

Part 1: Hot—demonstrating that heating water causes it to bubble and then turn into steam so that eventually all of the water will be gone from the container as the gas expands to fill the area. To raise the rigor, have students collect temperature readings and graph over time and/or measure the amount of water remaining after a few minutes of boiling and/or do in a pot with a clear lid so that students can see the water vapor condensing. This first set of water experiment links to popcorn by letting students see what is happening inside the kernel. To demonstrate that the water vapor takes more room and so increases the pressure inside the hull, attach a non-latex glove securely to the mouth of a flask. As the water changes phase, the glove will inflate. Adding rice to a clear pot will allow the students to see more clearly how the hottest water rises but then starts to cool as it moves away from the heat source and begins to fall back down lacking the energy to transition to water vapor. This cycle is repeated until all of the water reaches the required energy state. On a side note, the rice experiment will also help students develop an understanding of plate movement due to the very slow movement of magma under the crust.

Part 2: Cold—fill a plastic container to the top with water, lay the cover on top but don’t seal it, put in the freezer and check the next morning. This activity helps students to discover that water expands when it freezes and that if you let the ice thaw it will fit back into the container. As an extension, have students fill plastic water bottles to the very top and put them in the freezers. In most cases, the ice will expand enough to crack the plastic bottle. This demonstration of filling, freezing and cracking sets students up to understand frost wedging as a principle force of weathering later. This is a good place to look at the molecular structure of water and have students make simple models using toothpicks and marshmallows. More advanced students could consider the valence models of the two elements, and their electronegativity patterns from the periodic chart. This is also a good place to revisit the idea of density. In elementary school, students develop the idea that heavy things sink and lighter things float. In middle school, that understanding is expanded to include the idea of density. Heavy things can float as long as their overall density is less than the substance in which they are floating. The phenomenon of water floating on water is a great entry point. Students can then build density columns using only water, food coloring, and either salt or sugar. As in the heat experiment, students can also collect temperature data over time as a cup of ice changes state to room temperature water. Since my students will all have Chrome books this year, I will incorporate technology by using temperature probes and the Sparkvue software that will collect and graph temperature changes over time. It will allow students to see that there isn’t a temperature change until there is a complete phase change.

Part 3: Heat by the Numbers—why do animals huddle together in the cold? This set of experiments is designed to help students discover that heat energy always moves from higher energy to lower energy, hot to cold. To start, heat water until it steams. Then stop and pour into a jar, cover with plastic wrap, and then take the temperature every two minutes until there is no change over three successive readings. Repeat experiment but this time do it with four jars that touch, wait until the four are at the same temperature as the one, then record temperatures every two minutes. Continue until the four jars match the temperature of the one jar. Students can then graph both sets of data as temperature compared to elapsed time. The last experiment gets into the idea of surface area. It isn’t that heat is only being lost on the outside. It is that the temperature difference is much less where the surfaces are touching. A variation would be to use five jars, one in the center and four outside and note any differences. To demonstrate that different substances react to heat and cold differently, students could investigate how other substances, like most metals, expand when hot but contract when cold. The differing expansion of metals when heated is behind most thermostats, including the ones found in many popcorn poppers. To discover that water is not the only substance that expands when cooled, students should do the following rubber band experiment. Suspend a paper clip in a shoebox from a rubber band at room temperature and mark the placement. The box assembly is then put in the refrigerator for 20 minutes and then the clip position is marked. Lastly, the room temperature rubber band is heated with a hair dryer for 5 minutes and then the clip position is marked. Students will see that although most substances get larger when they are heated and smaller when they are cooled (think of how we demonstrate increased kinetic activity) rubber bands do the opposite.

Part 4: Engineering a Solution—putting it all together.

Using what they have learned about the transfer of heat energy from hot to cold, students will work in groups to create an insulated drink cooler from commonly found materials. Each group will start with the same size ice cube in a small paper cup. In order to monitor the state of the ice cube, the cooler must have an easily removable and replaceable lid. Students will have to create a design plan before they “shop” for materials. Whenever I give a design challenge, I try and provide a variety of items, some that I know will be more useful than others but I still let students decide. For this challenge, items would include cups of different sizes in paper, plastic, and Styrofoam. Fastening materials would include glue, scotch tape, masking tape, duct tape, string/yarn and a stapler. Insulating materials would include old file folders, plastic wrap, aluminum foil, wax paper, bubble wrap, plastic straws and pieces of material-cotton, wool, and synthetic blends. Paper would be available in both copy weight, construction and cardstock in a variety of colors. As in the real world, there are different costs associated with each. Styrofoam, aluminum wrap and duct tape will be more expensive than file folders, plastic wrap and masking tape. The “coolers” will be tested outside on the tennis courts. Graphic design is a huge thing in middle school. Different colors and types of paper will be available for decorating their containers. Although I won’t talk directly about color and heat absorption, some students may have background knowledge from elementary school. As part of the weather kit in first grade, students took temperature readings of thermometers left in the sun in either white or black sleeves. For each item chosen, students have to justify why that material was selected. An example might be that even though Styrofoam is four times the cost of the file folder, it is a better insulator and is also water tight. The winning container will have the longest ice cube melt time at the lowest cost. This is similar to another activity that comes later in the semester when students create earthquake resistant houses. To encourage students to do more thinking in the design phase rather than guess and try, I institute fees for both additional shopping trips and restocking.  

Days 15-19 Student Designed Investigation

Students design, conduct, and analyze the results of a question of their own choosing connected to popcorn. This investigation has been broken down into several parts as shown.

The Science of Popcorn

Students will use the science and engineering practices of the NGSS to investigate a question of their own choosing connected to the science of popcorn.

Students have a choice to share their work as a power point/Google slide presentation, a poster, a written lab report, an oral presentation with visual aids or another format discussed with and approved by the teacher.

My topic is:

I plan to share my work as:

Teacher’s signature

Step 1: Generating a Testable Question

What would you like to know? Question needs to relate in some way to popcorn.

Requires Teacher signature before moving on to next step.

_______________________________

Step 2:  Personal Background Knowledge

What do you think you already know about this topic that might help you form your hypothesis? Write three to five sentences in one paragraph about your prior knowledge before you do any other background research.

Step 3: Background research

Your work must be at least two paragraphs of four to six sentences. It must contain at least four facts and details related to your topic. Information needs to be in your own words and not just copied and pasted from your sources. You need to use and cite at least 2 sources. Sources may include books, web sites, videos, articles and/or interviews with experts in the field. Make sure that your source is credible. Wikipedia may only be used as a starting point to get sources; it does not count as one of your two sources.

Requires teacher signature before moving on to next step.

Step 4: Develop a Testable Hypothesis related to the Topic of Popcorn

This may differ from your original testable question. Remember a testable hypothesis is a statement that can be supported by data.

Requires Teacher signature before moving on to next step .

Step 5: Design an experiment to test your hypothesis . Describe any anticipated safety issues and how you plan to address them.

Be sure to only look at one variable at a time and keep the other variables the same. Include clearly labeled data table(s) with units. Remember multiple trials. My goal is for students to do their investigations in the classroom. I will have heat sources and a microwave available. I will also provide basic popping corn. Since they are student designed, it may be possible that a home component is needed. If that is the case, it needs to be approved by both the parents and myself in this stage of the project.

Requires parent signature before moving on to next step.

Step 6: Conduct your experiment. Prior to doing any experiments, we will review the science safety rules.

Gather the data.

Step 7: Analyze your data.

What patterns do you see? How can you use graphs, pictures and math to better convey your findings?

Step 8: Write your Conclusion

Revisit your hypothesis. Do your data support or not support it? What is your evidence? How does the evidence connect to your claim?

Step 9: Experimental Notes

Reflect qualitatively on the experience. What, if anything, happened that you didn’t anticipate? What affect do you think it had on your results?

Step 10: Next Steps

Based on what you learned from this experiment, what question would you like to investigate next? Write a brief three to five sentence paragraph about your new question and possible investigation.

Popcorn Science Investigation Ideas (Scaffolding for students who are unable to generate their own question)

Possible Questions:

Which pops more, Orville Redenbacher or Paragon?

Options-microwave, pot on “stove”, table top popcorn maker

Which pops bigger, Orville Redenbacher or Paragon?

Options-microwave, pot on “stove”, tabletop popcorn maker

-bigger in average popped kernel size or bigger in total volume

Which heat source pops loose corn better?

Options-microwave compared to either pot on “stove” or tabletop popcorn maker

How does using oil affect the amount of kernels popped?

Options-pot on “stove,” tabletop popcorn maker

How does using oil affect the size of kernels popped?

How does the type of oil affect the amount of kernels popped?

Options-corn, canola, coconut

How does the type of oil affect the size of kernels popped?

How does the type of oil affect the taste of kernels popped?

Scoring Rubric for Popcorn Science Investigation

Students are to design, conduct and analyze the results of an experiment of their own choosing connected to Popcorn. The plan is to do the bulk of the work in class. There are built-in checkpoints along the way.

Teacher Resources

Education World: Popcorn Science. Accessed July 17, 2017. http://www.educationworld.com/a_lesson/03/lp324-05.shtml.

Provides descriptions of several k-8 student investigations with the nature of math, nature of language and nature of science standards. Easy to read teacher format but standards need to be aligned to common core and NGSS.

• 16 Indian Inventions, From Popcorn to Parkas, Accessed July 27, 2017. http://news.nationalgeographic.com/news/2004/09.
• Types of Corn. Accessed July 17, 2017. http://www2.kenyon.edu/projects/farmschool/food/corntyp.htm.

On-line resource that discusses the different types of corn and the properties of each.

Beauchamp, Arthur, Judi Kusnick, Rick McCallum, and Jim Hollander.  Success in Science through Dialogue, Reading and Writing . Davis, CA: University of California, Davis, 2011.

• BolderImage. "History." Cretors. Accessed July 17, 2017. http://www.cretors.com/page.asp?i=12.

Provided the history of commercial popcorn machines.

Bybee, R. W.  Next Generation Science Standards. for States, by States . Washington, D.C.: National Academies Press, 2013.

• Boutard, A. Beautiful Corn: America's Original Grain from Seed to Plate . Gabriola Island, B.C.: New Society Publishers, 2012.

This is a comprehensive book on corn. It provided most of the background knowledge on the different types of corn with the emphasis on everta.

Butler, S. "A History of Popcorn." History.com. December 06, 2013. Accessed July 17, 2017. http://www.history.com/news/hungry-history/a-history-of-popcorn.

Good background information on the history of popcorn.

Czerski, H. Storm in a Teacup: The Physics of Everyday Life . S.l.: W. W. Norton, 2018.

Hardback book that explains the physics of everyday events including what makes popcorn pop. The author does an excellent job connecting the physics of thermodynamics through different phenomena.

Cooper-White, M. "The Secret Science Behind Popcorn, Finally Revealed." The Huffington Post . February 12, 2015. Accessed July 17, 2017. http://www.huffingtonpost.com/2015/02/12/popcorn-physics-science-pops-video_n_6664166.html.

Straightforward description of the process and slow motion video of a kernel popping.

Evans-Hylton, P. Popcorn . Seattle, WA: Sasquatch Books, 2008.

Provides some background knowledge but is mainly a recipe book of more than 60 ways to serve popcorn.

• "General Mills v. Hunt-Wesson, Inc., 917 F. Supp. 663 (D. Minn. 1996)." Justia Law. Accessed July 17, 2017. http://law.justia.com/cases/federal/district-courts/FSupp/917/663/2140347/.

Transcript of the court case. It provides interesting information and might also be used as background knowledge as part of an invention unit as well as this popcorn unit.

Jorgenson, O., Vanosdall, R., Massey, V., and Cleveland, J.  Doing Good Science in Middle School: A Practical STEM Guide: Including 10 New & Updated Activities . Arlington, VA: NSTA Press, National Science Teachers Association, 2014.

Excellent resource that describes different effective strategies on doing science with middle schoolers.

Koss, A. G., and Bryant, L. J. Where Fish Go in Winter: And Other Great Mysteries . New York: Dial Books for Young Readers, 2002.

This book is the source of the poem “Why does popcorn pop?” With simple language and rhyme, it captures the science of popcorn.

• Levy, J. Incredible Elements: A Totally Non-scary Guide to Chemistry and Why It Matters . New York: Metro Books, 2017.

This book provides simple explanations with strong graphic support for several of the key concepts of my research including phases, the nature of water, the application of heat and heat capacity.

Moulding, Brett D., Rodger Bybee, and Nicole Paulson.  A Vision and Plan for Science Teaching and Learning: An Educator's Guide to a Framework for K-12 Science Education, next Generation Science Standards, and State Science Standards . Place of Publication Not Identified: Essential Teaching and Learning, 2015.

Nuwer, R. "Popcorn Physics 101: How a Kernel Pops." Scientific American . Accessed July 17, 2017. https://www.scientificamerican.com/article/popcorn-physics-101-how-a-kernel-pops/.

Explains both the sound and the spring like action. Using slow motion camera identifies the starch molecules reforming into leg like appendages.

• "Percy Spencer." NNDB. Accessed July 17, 2017. http://www.nndb.com/people/766/000165271/.

Background information on the inventor of the microwave oven.

"Percy Spencer." Famous Inventors. Accessed July 17, 2017. http://www.famousinventors.org/percy-spencer.

Background information on the invention and inventor of the microwave oven.

Perlman, S. "The Physics of Popcorn." Prezi.com. May 19, 2015. Accessed July 17, 2017. https://prezi.com/v1tmfz0ovt_x/the-physics-of-popcorn/.

Could be used by teacher as part of a flipped classroom or introduction. One caution is the use of Charles’ Law which deals with the change in volume rather than the change in pressure.

"Popcorn." Andreoli S.A. Accessed July 17, 2017. http://www.andreolisa.com.ar/popcorn.html.

Gives information about the export of popcorn from Argentina.

"The Science of Popcorn." Carolina Biological Supply: World-Class Support for Science & Math. Accessed July 17, 2017. http://www.carolina.com/teacher-resources/Interactive/the-science-of-popcorn/tr23952.tr.

Step by step lab to investigate pressure using popcorn. Would not be suitable for middle schoolers as it involves Bunsen burners. May be able to do it as a demonstration with either a hot plate or convection burner. Safety concerns over the heat source, high temperatures of the oil and popcorn breaking free of its aluminum foil cover

Severson, K. "Heirloom Popcorn Helps a Snack Reinvent Itself." The New York Times. September 30, 2014. Accessed July 27, 2017. https://www.nytimes.com/2014/10/01/dining/heirloom-popcorn-helps-a-snack-reinvent-itself.html.

News article that could serve as a close reading piece for bias and also as background research for a taste test experiment.

• Sobey, E. J. C. The Way Kitchens Work: The Science behind the Microwave, Teflon Pan, Garbage Disposal, and More . Chicago, IL: Chicago Review Press, 2010.

"The Thermodynamics of Popcorn." YouTube. December 10, 2014. Accessed July 17, 2017. https://www.youtube.com/watch?v=TZTpSZsS9mo Dec 10, 2014 - Uploaded by Jenni Domanowski.

Good video with slow motion capture of popcorn popping. It also has an extensive reference list.

Wolke, R. L., and Parrish, M. What Einstein Told His Cook: Kitchen Science Explained . New York: W.W. Norton & Co., 2008. In addition to discussing popcorn, this book also explains the way magnetic induction and microwave ovens work as two of the sources I will look at to generate the heat.

[email protected]. "Popcorn Neutrinos." Ice Cube - South Pole Neutrino Detector. Accessed July 17, 2017. https://icecube.wisc.edu/outreach/activity/popcorn_neutrinos.

This lab uses closed air poppers as it seeks to connect the change in mass from before and after popping to neutrinos. In a middle school level, the focus could be change in mass due to the loss of the water as it changed state from a liquid to steam. It presents an interesting extension in using a motion detector to look at energy or doing different things to the seed coat to try and affect the outcome of the experiment.

Student Resources

Amy Cowen on August 19, 2016 7:30 AM. "Popcorn Popping Science." Science Buddies. Accessed July 17, 2017. http://www.sciencebuddies.org/blog/2016/08/popcorn-popping-science.php.

Linked to Scientific American, it presents a stem lesson that students can do at home or in a home economics classroom as it requires an oven.

Cobb, V. Science Experiments You Can Eat . New York: Lippincott, 1972.

Describes experiments that students can do using popcorn and other items found in the kitchen.

• DePaola, T. The Popcorn Book . New York: Scholastic, 1978.

For many years, this has been the most popular of the elementary school books about popcorn. It has colorful illustrations and presents a great deal of information about popcorn in student friendly language.

Doudna, K. The Kid's Book of Simple Everyday Science: Amazing Experiments--no Lab Required . Minneapolis, MN: Scarletta Kids, 2013.

Provides experiments that look at heat transfer in a variety of ways, including making popcorn.

Higgins, N. Fun Food Inventions . Minneapolis: Lerner Publications Company, 2014.

Provides background information that is written at a middle school level.

Kudlinski, K. V., and Wexler J.  Popcorn Plants . Minneapolis, MN: Lerner Publications, 1998.

For students who have had little exposure to a traditional science textbook, this is a great start. It has a table of contents, an index and a glossary. There is even a section aimed at adults/parents on how to share the book with a child. The author does a very good job of describing the biology of the popcorn plant. There is strong visual support with clear pictures of the parts of the plant at various stages with additional labeled diagrams that show the overall structure, the process of pollination and even how the plant makes its own food. Kudlinski does a thorough job covering the material while keeping it accessible to children through the use of shorter sentences and the repetition of key nouns.

Landau, E., and Lies, B.  Popcorn!  Boston, MA: Houghton Mifflin, 2003.

It presents the mostly non-fiction material in a variety of ways including a mini popcorn quiz with the explanations included. It then goes on to describe the corn plant, the popping mechanism, and the history of popcorn with humor and relatable language. Each section is clearly labeled by title and consists of just a few pages with strong visual support. There is even a small section toward the end labelled “Top Secret For Parents Only” that describes the nutritional value. To encourage students to do their own research, the last page lists both books and websites the author has found useful.

McCallum, A., and Hernandez, L. Eat Your Science Homework: Recipes for Inquiring Minds . Watertown, MA: Charlesbridge, 2014.

Students resource for information about the science of making corn pop with some suggested exploration activities.

"Science Fair Projects." Popcorn Board Learn For Kids Science Fair Projects. Accessed July 17, 2017. https://www.popcorn.org/Learn/For-Kids/Science-Fair-Projects.

Provides ideas and in some cases, details on science projects for students connected with popcorn.

"What Makes Popcorn Pop?" Wonderopolis. Accessed July 17, 2017. http://wonderopolis.org/wonder/what-makes-popcorn-pop.

Excellent resource to use in a flipped classroom. It provides solid facts with a reading that highlights key vocabulary words. There is even a quiz feature that students can use to test their comprehension. It also has student friendly text and even includes the myth of the demon living inside each kernel of popcorn. It would lend itself to a language arts extension of either reading other myths or creating other food myths. Would also lend itself to an art extension.

What Makes Popcorn Pop?: First Questions and Answers about Food . Alexandria, VA: Time-Life for Children, 1994.

Factual information presented using lower level vocabulary. It also discusses other foods besides popcorn.

Wood, R. W., and Brown, R. E. Heat Fundamentals: Funtastic Science Activities for Kids . Philadelphia, PA: Chelsea House, 1999.

Presents a variety of experiments that students can do using common materials that look at changes in state due to temperature changes.

Wyler, R., and Stewart, P. Science Fun with Peanuts and Popcorn . New York: Messner, 1986.

Gives background information and presents several different experiments that students can do with popcorn.

Next Generation Science Standards (NGSS)

MS-PS1-1 Matter and Its Interactions

Develop models to describe the atomic composition of simple molecules and extended structures.

MS-PS1-4 Matter and Its Interactions

Develop a model that predicts and describes changes in particle motion, temperature, and state of a pure substance when thermal energy is added or removed.

MS-PS3-3 Energy

Apply scientific principles to design, construct, and test a device that either minimizes or maximizes thermal energy transfer.

MS-PS3-4 Energy

Plan an investigation to determine the relationships among the energy transferred, the type of matter, the mass, and the change in the average kinetic energy of the particles as measured by the temperature of the sample.

MS-PS3-5 Energy

Construct, use, and present arguments to support the claim that when the kinetic energy of an object changes, energy is transferred to or from the object.

Common Core Math Standards  

MP.2 Reason abstractly and quantitatively

6.RP.A.1 Understand the concept of ration and use ratio language to describe a ration relationship between two quantities

6.SP.B.5 Summarize numerical data sets in relation to their context

Common Core ELA Standards

RST.6-8.1 Cite specific textual evidence to support analysis of science and technical texts, attending to the precise details of explanations or descriptions

RST.6-8.3 Follow precisely a multistep procedure when carrying out experiments, taking measurements, or performing technical tasks.

WHST.6-8.1 Write arguments focused on discipline content

WHST.6-8.7 Conduct short research projects to answer a question (including a self- generated question), drawing on several sources and generating additional related, focused questions that allow for multiple avenues of exploration.

• Kudlinski, K. V., and Jerome W.  Popcorn Plants . Minneapolis, MN: Lerner Publications, 1998.
• Severson, K. "Heirloom Popcorn Helps a Snack Reinvent Itself." The New York Times. September 30, 2014. Accessed July 27, 2017. https://www.nytimes.com/2014/10/01/dining/heirloom-popcorn-helps-a-snack-reinvent-itself.html
• Andreoli S.A. "Popcorn." Accessed July 17, 2017. http://www.andreolisa.com.ar/popcorn.html
• Butler, S. "A History of Popcorn." History.com. December 06, 2013. Accessed July 17, 2017. http://www.history.com/news/hungry-history/a-history-of-popcorn
• "Percy Spencer." FAMOUS INVENTORS. Accessed July 17, 2017. http://www.famousinventors.org/percy-spencer.
• Wolke, R. L., and Parrish, M. What Einstein Told His Cook: Kitchen Science Explained . New York: W.W. Norton &, 2008.

Comments (0)

Be the first person to comment

Using Popcorn to Practice Scientific Method

This is a fairly common science fair project that I actually helped my grandson carry out for an elementary science fair. It’s definitely not a new idea, but a great way to let children work through the scientific method using a fun topic . . . POPCORN! The question to be answered is: “Does storage temperature affect how well popcorn pops?” Children will be storing popcorn in a warm environment, room temperature, cold, and frozen. Before beginning the experiment, encourage students to make a Hypothesis. Ask them to decide which storage method they think will work best, and why.

Materials: large bag of loose popcorn (not the individual “flavored” bags), baggies, paper lunch sacks, access to a microwave

Here’s the procedure we used, but it’s important to let your child come up with the procedure if this is to be a scientific method experiment.

1. Put 100 popcorn kernels in a plastic baggie and label as “warm.” Repeat with 3 more baggies, labeling them as “room temperature,” “cold,” “frozen.”

2. Place the baggies in the appropriate area. For example, store the “warm” bag under an electric blanket, the “room temperature” bag in the pantry, the “cold” bag in the refrigerator, and the “frozen” bag in the freezer. Select a specific time for storage, such as a week, a month, etc.

3. After the storage time is complete, remove the bags from their storage area at the same time. To test the storage methods, divide out the 100 popcorn kernels between 5 paper lunch sacks, with 20 kernels in each bag. Label each paper sack with the appropriate storage method. Repeat with all the remaining popcorn, being sure to label each paper sack with the correct storage method!

4. Decide on a specific popping time. Somewhere around 2 minutes works best, but any time will work if it gives the popcorn time to pop and you keep the time the same for all trials.

5. Put one of each sack of popcorn into the microwave at the same time. (In other words, place one sack that contains popcorn stored as “warm,” one sack with “cold” popcorn, etc. Turn on the microwave for the specified time. After the time has elapsed, remove the bags and count the number of kernels that popped. Record. Repeat until all the popcorn has been tried.

Data: Here’s a sample data table that can be used to record the results. For older children you may want to let them design their own table.

Older children can find the average of each type. For younger children who may not understand the concept of averaging, change to “Total” for the last column.

Analysis: Younger children can compare the totals to see which storage method resulted in more popped kernels. Older children can graph the results for a visual representation.

Conclusion: Have students state out loud, or write down, which storage method produced the most popped popcorn. Why do they think this method worked best? Also have them refer back to their original hypothesis. Was their hypothesis right or wrong?

HINT: Based on experience, don’t try to pop one bag at a time in the microwave. There will not be enough water in the popcorn to absorb the microwaves and the appliance will overheat! Mine actually stopped working for awhile! Popping four bags at a time worked well for us, but do feel the sides of the microwave after the first round to make sure it isn’t overheating. Take breaks between rounds if needed.

ALTERNATE METHODS: Children can also come up with their own idea of what to test, such as light vs dark, storage time, type of storage container, etc. The more children are able to make the experiment their own, the better!

BACKGROUND: Depending on the age of your child, You may also want to have them research WHY popcorn pops. Here’s a great website that explains the science of popcorn, as well as some interesting history: http://www.popcorn.org/Facts-Fun/What-Makes-Popcorn-Pop .

Blog Categories

• Cells and Microbiology
• Ecology – Ecosystems
• Acids and Bases
• Interactions of Matter
• Properties of Matter
• Water and Solutions
• Earth in Space
• Earth Materials
• Earth's Atmosphere
• Earth's History
• Teaching Science

Previous Post Don't Miss the Supermoon!

Next post roadcuts - windows to the past, you may also like.

How do you rate in general Scientific Knowledge?

An official website of the United States government

The .gov means it’s official. Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

The site is secure. The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

• Publications
• Account settings

Preview improvements coming to the PMC website in October 2024. Learn More or Try it out now .

• Advanced Search
• Journal List
• J R Soc Interface
• v.12(104); 2015 Mar 6

Popcorn: critical temperature, jump and sound

Emmanuel virot.

1 CNRS UMR 7646, LadHyX, École Polytechnique, 91128 Palaiseau, France

Alexandre Ponomarenko

2 LIPhy, CNRS UMR 5588, Grenoble University, 38401 Grenoble, France

Popcorn bursts open, jumps and emits a ‘pop’ sound in some hundredths of a second. The physical origin of these three observations remains unclear in the literature. We show that the critical temperature 180°C at which almost all of popcorn pops is consistent with an elementary pressure vessel scenario. We observe that popcorn jumps with a ‘leg’ of starch which is compressed on the ground. As a result, popcorn is midway between two categories of moving systems: explosive plants using fracture mechanisms and jumping animals using muscles. By synchronizing video recordings with acoustic recordings, we propose that the familiar ‘pop’ sound of the popcorn is caused by the release of water vapour.

1. Introduction

Popcorn is the funniest corn to cook, because it jumps and makes a ‘pop’ sound in our pans. Some other types of corn also produce flakes, such as flint corn or dent corn, but in a far less impressive extent [ 1 ]. In this article, we will focus on one type of corn (popcorn) for discussing the physical properties of popping. Early studies have focused on conditions required for successful popping of popcorn [ 1 – 3 ], conditions that are closely related to the fracture of the pericarp (outer hull) [ 4 ]. In this way, popcorn has been bred over the years for improving popping expansion [ 5 ]. When the popcorn temperature exceeds 100°C, its water content (moisture) boils and reaches a thermodynamic equilibrium at the vapour pressure, as in a pressure cooker [ 6 ]. Above a critical vapour pressure, the hull breaks. At the same time in the popcorn endosperm, the starch granules expand adiabatically and form a spongy flake of various shapes [ 7 – 10 ], as shown in the insets of figure 1 . Then, the popcorn jumps a few millimetres high to several centimetres high and a characteristic ‘pop’ sound is emitted. To the best of our knowledge, the physical origin of these observations remains elusive in the literature. Here we discuss the possible physical origins with elementary tools of thermodynamics and fracture mechanics.

Percentages of popped popcorn in an oven at increasing temperature (50 tests); the dashed line is a guide to the eyes. The critical temperature T c is approximately 180°C. (Insets) Snapshots of unpopped popcorn (kernels, left) and popped popcorn (flakes, right). (Online version in colour.)

Recently, many biological material fractures have been highlighted: these fractures allow plants and fungi to disperse their seeds and spores, respectively [ 11 – 15 ], or corals to colonize new territories by their own fragmentation [ 16 , 17 ]. Mammals do usually not need fracture for moving: they can use instead their legs as springs and form a single projectile with their whole body [ 18 ]. Equisetum spores have a similar mechanism for catapulting themselves with their elaters [ 19 ].

2. Warm-up: the critical temperature

To first understand the origin of the temperature at which popcorn pops, microwaveable pieces of popcorn from a single lot (Carrefour, ‘Popcorn’) are placed in an oven at temperatures increasing by increments of 10°C and lasting 5 min. We observe in figure 1 that only 34% of popcorn are popped at 170°C (17 out of 50). Instead, 96% of popcorn are popped at 180°C (48 out of 50), suggesting a well-defined critical temperature close to 180°C. This is consistent with previous measurements [ 6 , 20 , 21 ], i.e. in the range 177−187°C.

Table 1.

Popcorn properties before popping (kernel) and after popping (flake). Mean values ±s.d. on 41 measurements.

Change in the properties of popcorn. ( a ) Distribution of popcorn radius before and after popping. ( b ) Distribution of mass density; popcorn becomes two times larger and eight times less dense. (Online version in colour.)

3. Break dance: the popcorn jump

To explore further the dynamic of popcorn during its transformation, a piece of popcorn laid on a hot plate is recorded with a high-speed camera Phantom v9 at 2900 frames per second. The hot plate is set at 350°C whereas the room temperature is 20°C, so that the popcorn is partly heated at the required temperature T c = 180°C. A flake is formed after approximately 1 min of rest on the hot plate. An example is reported in figure 3 a . After the fracture of the popcorn hull and the beginning of starch expansion (see the snapshot at 6.9 ms), we observe the formation of a ‘leg’ which is compressed on the plate (at 13.8 ms). This leg bounces and the popcorn jumps (at 20.7 ms). We do not observe motion during the ejection of vapour (no rocket effect).

Fractures and jumps. ( a ) Snapshots of the somersault of a piece of popcorn while heated on a hot plate, 350°C (see electronic supplementary material, movie S1). We assume that the displacement in the y -direction is small compared to the displacements in the x–z plane because the kernel stays in the depth of field of the camera which is about 3 mm. ( b ) The fracture of Impatiens glandulifera seedpod, adapted from Deegan [ 13 ]. ( c ) The snapshots of the somersault of a gymnast, adapted from Muybridge [ 26 ]. (Online version in colour.)

This expression has a maximum θ m for α = 1/2, i.e. when the available energy is shared equally among vertical and rotary kinetic energy

Dimensionless coordinates of the mass centre ( x / R k , z / R k ) and evolution of the angle of rotation θ for the jump of figure 3 a . Initial velocities are indicated with arrows. The dragless Galilean parabola (dashed line) fits well the trajectory. (Online version in colour.)

Rotation angles (in deg.) measured as a function of the predicted one, equation ( 3.1 ). The data collapse on a straight line of slope 1 in logarithmic scales. (Online version in colour.)

Since the maximum rotation angle θ m ∼ E 0 /( ρgR 4 ) is also a dimensionless number which compares the energy E 0 released by the legs to a characteristic gravitational energy of the body of mass density ρ and size R , we can use it as a rough indicator of performance. In the situation of a jump done with muscles, we have E 0 = F m × l m , where F m ∼ R 2 stands for the muscle force (proportional to the number of muscle fibres in the body section) and l m ∼ R being the muscle elongation proportional to the body size. Consequently, the performance θ m of a jump executed with muscles should scale inversely with the body size. However, the popcorn is thousand times smaller than gymnast though they have rather the same performance θ m . As already pointed out, the jump of popcorn relies on a highly dissipative mechanism instead of muscle elasticity.

4. Pop music: the popcorn sound

To the best of our knowledge, little attention has been paid so far to the origin of the characteristic ‘pop’ sound. In our scenario, this sound could be caused by (i) the crackling fracture, (ii) the rebound on the ground or (iii) the release of pressurized water vapour.

To understand the origin of the ‘pop’ sound, a microphone Neumann KM 84 (40–16 000 Hz) is added to our experimental set-up. The microphone is set 30 cm away from a piece of popcorn laid on a hot plate. The acoustic recording is synchronized with a high-speed camera Phantom Miro 4 (2000 frames per second) by the break of a pencil lead, for an error less than 1 ms.

As shown in figure 6 a,b , the popcorn first opens part of the starch without emitting any sound. Then, after 100 ms, a second fracture starts ( figure 6 c ), followed by the start of the ‘pop’ sound 6 ms later ( figure 6 f ). Both fractures enlarged, while the leg of starch continues its course towards the hot plate. The ‘pop’ sound, starting at 106 ms, lasts approximately 50 ms, without a clear dominant frequency, but with sharp bursts at 110, 115 and 121 ms ( figure 6 f ).

‘Pop’ sound recording synchronized with high-speed imaging (see electronic supplementary material, movie S2). ( a–e ) The snapshots of the piece of popcorn are separated by 50 ms. ( f ) A ‘pop’ sound is observed during the fracture of the popcorn and before any jump. (Online version in colour.)

We first see that the ‘pop’ sound is not caused by the rebound because it occurs before any jump. Careful observations also discriminate crackling noises because the most part of fractures on the pieces of popcorn are not correlated to any sound (see also [ 31 ]). Then, it is reasonable to hypothesize that the ‘pop’ sound is triggered by the vapour release. More precisely, the pressure drop excites cavities inside the popcorn as if it were an acoustic resonator. Such a scenario has been applied to volcano acoustics and to the ‘pop’ of champagne bottle cork [ 32 ]. The bursts observed in figure 4 f can then be interpreted as successive releases of pockets of pressurized water vapour triggering successive excitations. Also, since the room where experiments are performed has reflective surfaces a few metres from the popcorn, the successive bursts can irremediably be associated with recurring artefacts from echoes. The short time delay of 6 ms between the fracture and the ‘pop’ sound can be interpreted as the time needed to reach and release the first pocket of vapour. The absence of a dominant frequency in our acoustic recordings remains surprising but it mirrors the drastic modifications of the properties of popcorn during its transformation.

5. Conclusion

Acknowledgements

Hearty thanks to Christophe Clanet for encouragements and enlightening suggestions. We wish to thank Stéphane Douady, Sébastien Moulinet and Mokhtar Adda-Bedia for helpful discussions. We warmly thank Gaspard Panfiloff for the microphone Neumann KM 84 and we are grateful to Loïc Tadrist and Karina Jouravleva for valuable comments on the manuscript.

Popcorn Science Experiment

Have you ever thought about what happens when you pop popcorn? How does a small hard kernel become a big puffy piece of popcorn? Does the unpopped popcorn weigh the same as the popped popcorn? Satisfy your curiosity with this popcorn science experiment.

What You’ll Need:

• Popcorn kernels
• Containers for weighing
• Saucepan and lid
• Oil (we use peanut oil but any neutral oil will do)

Cover the bottom of your saucepan with one layer of popcorn kernels. How many kernels did you use? (We used 70.) Use a kitchen scale to weigh your kernels. Place a container on the scale and tare (or zero) the scale. Add the kernels to the container. How much do your unpopped kernels weigh? Record this number.

Get ready to pop your popcorn. You’ll need to weigh your oil before popping. Place your pan on the scale and tare (or zero) the scale. Add enough oil to just cover the bottom of the pan (that was 1/4 cup for our pan.) Record this number.

Have an adult follow the recipe for the Perfect Stovetop Popcorn below.

Weigh your popped popcorn. Place a large bowl on your scale and tare (or zero) the scale. Pour the popcorn into the bowl. Record this number.

Compare the weights of your unpopped and popped popcorn. Do the kernels and oil weigh the same as the popped popcorn? Why or why not?

You can also try this popcorn science experiment with an air popper to eliminate the oil variable. (A small amount of oil remains on the pan and lid. This will affect your weights slightly.)

The Science Behind It

Of all of the different types of corn, only popcorn pops. It has the right moisture content and hull thickness to make the yummy snack we’re so fond of. As the popcorn kernel heats up, the water inside changes to steam and exerts pressure on the hull of the kernel.  Eventually, the hull bursts open, the inside of the kernel spills out, and it cools into fluffy white popcorn. It’s the loss of water that causes the change in weight between the unpopped and popped popcorn. Read about the science and history of popcorn and more details about what makes popcorn pop from the Popcorn Board.

How Much Popcorn Popped?

According to the Popcorn Board, 1 ounce (28 grams) of popcorn kernels will make 1 quart of popped popcorn. Is this figure consistent with your experiment? How much popcorn did you pop?

Perfect Stovetop Popcorn

• Add enough oil to just cover the bottom of the pan.
• Add a single layer of popcorn kernels to the pan.
• Place the pan over medium high heat. Wait until the popcorn kernels begin to pop.
• Shake the pan until the popcorn finishes popping – about 3 minutes. When the popping slows to 2 seconds between pops, it is finished.
• Remove from heat.
• Add salt and any additional toppings.

More Science Experiments for Kids

• Set up this banana experiment to determine which banana will ripen first.
• Learn how to build a lemon battery in this sponsored post.
• Conduct this layering liquids density experiment with fruit juices.

Subscribe to the Inspiration Laboratories newsletter. Each issue has exclusive hands-on science explorations for children, a recap of our latest activities, and special resources selected just for you!

Leave a Reply Cancel reply

Your email address will not be published. Required fields are marked *

Save my name, email, and website in this browser for the next time I comment.

© 2024 Inspiration Laboratories

Science Fair Projects

What Makes Popcorn Pop?

People have been fascinated by popcorn for centuries. Native Americans believed that a spirit lived inside each kernel of popcorn. When heated, the spirit grew angry and would eventually burst out of its home and into the air as a disgruntled puff of steam. A less charming but more scientific explanation exists for why popcorn pops.

Popcorn is scientifically known as Zea mays everta. It’s a type of maize, or corn, and is a member of the grass family. Popcorn is a whole grain and is made up of three components: the germ, endosperm, and pericarp (or hull) . Of the 4 most common types of corn —sweet, dent (also known as field), flint (also known as Indian corn), and popcorn—only popcorn pops! Popcorn differs from other types of corn in that its hull has just the right thickness to allow it to burst open.

As the kernel heats up, the water begins to expand. Around 212 degrees the water turns into steam and changes the starch inside each kernel into a superhot gelatinous goop. The kernel continues to heat to about 347 degrees. The pressure inside the grain will reach 135 pounds per square inch before finally bursting the hull open.

As it explodes, steam inside the kernel is released. The soft starch inside the popcorn becomes inflated and spills out, cooling immediately and forming into the odd shape we know and love. A kernel will swell 40-50 times its original size!

Where to Begin an Experiment?

There are a lot of experiments you can try using popcorn. First, you need to figure out what you want to compare and what you can measure. For example:

• White vs. yellow
• Flavor vs. plain
• Methods of popping: microwave, stovetop, or air popper
• Size/amount of kernels
• Storage temperature for kernels
• Storage conditions (moisture, dryness) for kernels
• Popping time
• Total number of kernels popped or unpopped
• Percentage of popped kernels
• Volume of popcorn produced
• Weight of popcorn produced
• Average size of popped corn
• Time it takes to pop popcorn

For example:

• How does moisture affect popability?
• Which brand of microwave popcorn pops fastest?
• Which brand leaves the most unpopped kernels? 

Avoid questions like “Which brand tastes best?” because it is a subjective question and difficult to measure.

Make sure you replicate your experiment. It’s important to repeat your test at least three times. That means, if you’re comparing microwave popcorn for the number of unpopped kernels left after popping, you need to test 3 of the same type of bag per brand. Sure, that’s a lot of popcorn, but that just means you get to eat a lot of popcorn. Be smart: plan ahead and conduct your experiment over several nights.

Which Brand of Microwave Popcorn Pops Fastest?

If we had a dollar for every time we have been asked this question, we would be very, very wealthy. And if we had a dollar for every time we’ve answered it, we would be very, very poor.

First, we don’t mention or talk about brands. You might have a favorite popcorn brand, but we don’t. We love ALL American processed popcorn! But we appreciate that you’re doing a science fair project and you want a quick answer, which brings us to our second point: It’s your science fair project; you have to do your own experimenting and see what happens. The bad news is there’s no quick answer. The good news is that you get to eat lots of popcorn along the way.

General Measuring Rules

• 2 tablespoons of unpopped popcorn kernels will make about a quart popped
• 2 tablespoons = 1/8 cup = 1 ounce
• 8 ounces in a cup
• 4 ounces in ½ cup
• 4 cups in a quart
• 4 tablespoons = 1/4 cup which would yield about 2 quarts popped

Sample Experiments

The following are just a few of the experiments you can do using popcorn.

• Grow, Grow, Grow Your Popcorn   | Grades K-3
• How Much Water Does Popcorn Contain?   | Grades 5-6
• Comparing Brands | Grades 5-8
• Comparing Volumes | Grades 5-8
• The Effect of Moisture on Popcorn  | Grades 5-8
• Temperature Comparison Test   | Grades 5-8
• Popcorn Color Comparison  | Grades 5-8

You are now leaving the popcorn.org site and the Popcorn Board is not responsible for the information or views expressed on external sites.

• Foundations
• Write Paper

Search form

• Experiments
• Anthropology
• Self-Esteem
• Social Anxiety

• Kids' Science Projects >

Experiments with Popcorn

Experiments with popcorn are a fun way to test a scientific theory with the added bonus of having some tasty food to eat afterwards.

This article is a part of the guide:

• Kids' Science Projects
• Paper Towel
• Salt Water Egg
• Fruit Battery

Browse Full Outline

• 1 Kids' Science Projects
• 2 How to Conduct Science Experiments
• 3.1 Mold Bread
• 3.2 Popcorn
• 3.3 Salt Water Egg
• 3.4 Corrosiveness of Soda
• 3.5 Egg in a Bottle
• 3.6 Fruit Battery
• 4.1 Pendulum
• 4.2 Paper Towel
• 4.3 Paper Airplane
• 4.4 Charge a Light Bulb
• 4.5 Lifting Ice Cube
• 4.6 Magic Egg
• 4.7 Magic Jumping Coin
• 4.8 Invisible Ink
• 4.9 Making-a-Rainbow
• 4.10 Oil Spill
• 4.11 Balloon Rocket Car
• 4.12 Build an Electromagnet
• 4.13 Create a Heat Detector
• 4.14 Creating a Volcano
• 4.15 Home-Made Glue
• 4.16 Home-Made Stethoscope
• 4.17 Magic Balloon
• 4.18 Make a Matchbox Guitar
• 4.19 Make Your Own Slime
• 5.1 Heron’s Aeolipile
• 5.2 Make an Archimedes Screw
• 5.3 Build an Astrolabe
• 5.4 Archimedes Displacement
• 5.5 Make Heron’s Fountain
• 5.6 Create a Sundial

Popcorn is a food that has been around for many thousands of years, ever since people in America discovered that if corn (maize) was left next to a fire, it would 'pop' into fluffy and delicious shapes.

Ever since then, popcorn has become one of the most popular foods on earth, with movie-goers everywhere tucking into huge bucketfuls of the stuff.

There is a little more to popcorn than that, and we are going to design some experiments which will allow us to find out a little more about this fascinating food.

For these experiments with popcorn, it is best if you have a hot air-popper. If not, you will need to use a pan on the cooker (stovetop), so it is important to have an adult helping you.

You must also remember that popcorn is very hot when it comes out of the popper so handle with care. If you want to eat the popcorn afterwards, make sure that all your equipment and your hands have been washed properly.

Experiment 1 - Are Yellow or White Kernels the Best?

A good supply of both yellow and white popcorn kernels.

• A hot air popper or a pan, a 30 ml oil and a stove
• A large bowl
• A tablespoon
• A large measuring jug
• Chart for recording your results.

White kernels pop better than yellow kernels.

Manipulated (independent) Variable

The type of popcorn kernel.

Measured (dependent) Variable

The number of popped kernels and the volume after popping.

• First, you need to make yourself a data chart, like in Figure 1. You will use this to record the results of your experiments with popcorn.
• Count out 100 kernels of white popcorn, and heat until you can no longer hear any popping.
• Let everything cool down and then count the number of popped kernels. Record this on your chart. Because we counted 100 kernels, we can write this number down as a percentage.
• Tip the popped corn into a measuring jug and measure the volume in ml. Record these numbers on your chart.
• Repeat two more times for the white popcorn. In the same way, test the yellow kernels three times

You can take an average of your results for the percentage of popped kernels and the volume. Which color kernel pops better?

You can draw your results onto a couple of bar graphs and discuss your important findings with the rest of the class.

Follow Up Experiments

Maybe you could test different brands of popcorn to see which the best are. Does a hot-air popper do a better job than a pan? There are many ways you can design more experiments with popcorn.

Experiment 2 - Which is the Tastiest Popcorn?

For this experiment you will be trying to find out which brand of popcorn people like to eat most. You will be using a 'blind tasting' technique to find out which popcorn people like the most.

Brand 'X' is the best tasting popcorn.

• Five different brands of popcorn - it is best to stick to the same type e.g. all salted or all sweet to prevent personal taste becoming an issue.
• Some popcorn-loving volunteers
• Five labels, brand A, brand B etc
• A blindfold
• Tip a little of each popcorn into a bowl and make a note, with the labels, of which is which.
• Take one of your volunteers and blindfold them in case they recognize any of the brands. You must be very careful and make sure that they cannot trip over anything.
• Let them try each brand of popcorn, in turn, and give marks out of ten for how tasty it is.
• Make a note of your results in a table and add up the results for each brand of popcorn.

You can then plot a simple graph and you will know which brands are the tastiest!

There are many other experiments with popcorn you can do with this method. Maybe you could study whether more expensive brands taste better. Does the cost of the popcorn make a difference?

Figure 1 - Table for Experiment 1

• Psychology 101
• Flags and Countries
• Capitals and Countries

Martyn Shuttleworth (Jun 17, 2008). Experiments with Popcorn. Retrieved Aug 14, 2024 from Explorable.com: https://explorable.com/experiments-with-popcorn

You Are Allowed To Copy The Text

The text in this article is licensed under the Creative Commons-License Attribution 4.0 International (CC BY 4.0) .

This means you're free to copy, share and adapt any parts (or all) of the text in the article, as long as you give appropriate credit and provide a link/reference to this page.

That is it. You don't need our permission to copy the article; just include a link/reference back to this page. You can use it freely (with some kind of link), and we're also okay with people reprinting in publications like books, blogs, newsletters, course-material, papers, wikipedia and presentations (with clear attribution).

Want to stay up to date? Follow us!

Get all these articles in 1 guide.

Want the full version to study at home, take to school or just scribble on?

Whether you are an academic novice, or you simply want to brush up your skills, this book will take your academic writing skills to the next level.

Download electronic versions: - Epub for mobiles and tablets - For Kindle here - PDF version here

Save this course for later

Don't have time for it all now? No problem, save it as a course and come back to it later.

Footer bottom

• Privacy Policy

• Subscribe to our RSS Feed
• Like us on Facebook
• Follow us on Twitter

• Share full article

Why, Exactly, Are Ultraprocessed Foods So Hard to Resist? This Study Is Trying to Find Out.

Understanding why they’re so easy to overeat might be key to making them less harmful, some researchers say.

Supported by

By Alice Callahan

Photographs by Lexey Swall

Alice Callahan spent two days at the National Institutes of Health in Bethesda, Md., and interviewed more than a dozen researchers about ultraprocessed foods.

• Published July 30, 2024 Updated July 31, 2024

It was 9 a.m. on a Friday in March, and Ernest Jones III was hungry.

From a hospital bed at a research facility at the National Institutes of Health in Maryland, he surveyed his meal tray: Honey Nut Cheerios with fiber-enriched whole milk, a plastic-wrapped blueberry muffin and margarine.

Listen to this article with reporter commentary

“Simple, old school,” one of those “Saturday morning breakfasts from back in the day,” said Mr. Jones, 38, who is studying to become a pastor.

He was about halfway through his 28-day stay at the N.I.H., and Mr. Jones was one of 36 people participating in a nutrition trial that is expected to be completed in late 2025. For one month each, researchers will draw participants’ blood, track their body fat and weight, measure the calories they burn, and feed them three meticulously designed meals per day.

The subjects don’t know it, but their job is to help answer some of the most pressing questions in nutrition: Are ultraprocessed foods harmful to health? Are they a major driver of weight gain and obesity? And why is it so easy to eat so many of them?

If researchers can answer these questions, they say, perhaps there are ways to make ultraprocessed foods healthier.

We are having trouble retrieving the article content.

Please enable JavaScript in your browser settings.

Thank you for your patience while we verify access. If you are in Reader mode please exit and  log into  your Times account, or  subscribe  for all of The Times.

Thank you for your patience while we verify access.

Already a subscriber?  Log in .

Want all of The Times?  Subscribe .

Advertisement

What is a hypothesis for why does popcorn pop?

"I believe that Popcorn Brand A will pop more than Popcorn Brand B."

act III will be the best one because it comes with the most kernels

one hypothesis for "Why does popcorn pop," could be something like popcorn pops because when heated the outside shell peels off.

Add your answer:

Top Categories