Learning Objective: To develop a hypothesis and then perform an experiment on which color of popcorn kernels pops the biggest in order to confirm or invalidate the hypothesis.
Key Terms: Science, Popcorn, Scientific Method, Food Science
Grade Level: 5-8
- Supply of white and yellow popcorn kernels (if you can, there are red and blue kernels too)
- Hot air popper or a paper bag (this will be used to pop the popcorn kernels)
- Large bowl
- 2-quart measuring cup
- Plastic bag for white and yellow samples
- A ruler
Estimated Time: Approximately 30-45 min
Popcorn kernels (known as Zea Mays Everta) are one of six types of corn. However, popcorn kernels are unique for their ability to pop when heated. Popcorn kernels consist of three different layers
- Outer shell (known as the bran, hull, or pericarp) – protects the kernel from environmental factors.
- Endosperm – the middle layer that stores starch and water to feed the germ.
- Germ – is the seed embryo.
The water trapped in the endosperm turns to steam when the kernels are heated. This steam creates an immense amount of pressure, that when great enough causes the outer shells to give way resulting in the delectable snack we know as popcorn.
Corny Fact: the popped starch of the popcorn and its shape are called the flake.
Did you know that popcorn comes in many different varieties?
Popcorn kernels are most commonly categorized by their kernel color, size, and overall shape. When it comes to purchasing or making popcorn recipes, these specific characteristics can help you determine which one is the best for your use.
Popcorn Kernel Colors
The most popular kernel colors are yellow and white. Yellow kernels are most commonly seen for commercial use or used at movie theaters.
Less commonly known colors include kernels that are red, blue, and even purple.
While the kernels can come in a variety of colors, the flakes are always white, off-white, or yellow-ish, with the hull remaining the original color of the popped kernels.
White kernels: These types of kernels are typically used in home-popped popcorn and are smaller in size. The popcorn kernels tend to favor bright white or dusty white color.
White popcorn is known to have a sweeter taste as opposed to a savory or nutty flavor. The color of the popcorn remains a bright white once popped.
White kernels require minimal to no oil to cook. This popcorn tends to be higher in fiber making it the perfect crunchy, healthy snack.
Yellow kernels: These kernels will be the ones you see sold in movie theaters or in microwave popcorn. Yellow kernels have a pronounced kernel color that is usually between a bright yellow to a bright orange color. When popped, the kernel presents with a yellow, buttery tint.
Yellow kernels produce popcorn that is often crisp and nutty in flavor. This combination makes it a perfect popcorn to pair with salt and butter, or other savory options such as cheesy or spicy.
Red kernels: These kernels present with a beautiful deep red color. Red kernels tend to be smaller than most other kernels and also when popped.
Red kernels produce a white flake very similar to white kernels but they have a slightly nuttier flavor with a neutral taste. These are perfect for a healthy snack that packs a lot of flavor.
Red kernels can commonly be purchased at large grocery stores as they are popular enough to typically be stocked. Due to the fact that they are less common, but more sought after by popcorn purists, they tend to generally cost more than yellow or white kernels.
Purple kernels: These kernels are a deep purple color that comes naturally from a compound called anthocyanins.
Anthocyanins are a pigment found in plants that give a deep purple and blue appearance. They are powerful antioxidants known to help boost the immune system and fight inflammation.
Purple kernels produce larger and fluffier popcorn than red kernels. The hulls tend to be less tough, making them a great option for those with sensitive teeth.
Blue kernels: Similar to red kernels, these kernels produce white popcorn that is smaller in size, with a tender, light flake, and a nutty flavor.
The two most popular shapes of the flake are the “mushroom” and “butterfly” (also known as a “snowflake”).
The shape of the flake is not specific to a particular color of popcorn such as white or yellow popcorn. The different colored kernels can produce either a mushroom or butterfly-shaped popcorn.
Mushroom shape: Once popped, the mushroom popcorn produces a round, bulbous type of flake.
The mushroom flake is dense, yet tender allowing it to hold its shape. This flake is common to the popcorn industry because of its ability to hold its shape when covered in sugar, butter, chocolate, or other flavors.
Butterfly shape: These kernels resemble butterfly wings but in all directions. The butterfly shape is a bit more delicate compared to the mushroom shape.
The butterfly shape is soft, yet crisp. It’s recommended to use while it is fresh, as it can easily be ruined with moisture or toppings. It is best to use dry seasonings with this type of popcorn.
Popcorn kernel sizes don’t have standards, but there are simple measures to follow to categorize kernel size. However, they are commonly measured based on the number of kernels in 10 grams.
Large: If there are 52-67 kernels in 10g.
Medium: If there are 68-75 kernels in 10g.
Small: If there are 76-105 kernels in 10g.
Very small: If there are >105 kernels in 10g.
In experiments there are parameters that you would change and others that you would keep the same, these are called variables.
A variable can commonly be measured in some sort of way such as height, age, weight, temperature, etc. Variables contributing to the outcome of an experiment in any way.
The three different types of variables:
Independent variable: This variable is the one that can change in an experiment. This variable does not depend on any other variables.
For example, if you were to run an experiment on sunlight and the growth of a corn plant, you placed one corn plant in the sun and the other in the shade. The independent variable is the exposure to sunlight.
Dependent variable: This variable is what you observe or measure. Dependent variables change based on the independent variable.
For example, in the corn plant experiment, you could measure how much the plant grows every week. This is because the growth of the plant is dependent on the amount of sunlight.
Controlled variables: These are the variables that don’t change throughout the experiment. In science, these are the variables that you want to keep the same across all conditions.
For example, in the corn plant experiment, these are the variables that you want to “control” such as water and temperature. You would not want to give more water to the plant in the sunlight and then less water to the plant in the shade. This would create a bias in the results of the experiment. The difference in water might make us less certain that the sunlight was the reason for whatever result we measure.
Discuss other potential variables that are important to control for in an experiment.
A great method to remember which is the dependent variable and which is the independent variable: Try to place them into a sentence which uses the phrase “causes a change in.” Saying that “sunlight exposure causes a change in plant growth” makes sense. This tells you that the independent variable (sunlight) affects the dependent variable (plant growth). However, the inverse is not true, “Plant growth causes a change in sunlight exposure.”
The below popcorn experiment can help children better understand the difference between the three main variables: independent, dependent, and controlled variables.
Discussion: provide a variety of different examples to your class to help them get a better understanding of the difference between the types of variables.
Below are directions on how to conduct an experiment to test the difference in Volume, Number of Unpopped Kernels, Shape, and Size of popcorn based on the color of the kernel.
- Draw a data chart to record the final results that include the following: The control variables will be Yellow Kernel, Samples 1, 2, & 3 and White Kernel, Samples 1, 2, & 3. Results will include Volume, Number of Unpopped Kernels, Shape, and Size An example is provided below.
Note: Have the children determine what the three different variables are.
|Popcorn||Sample 1||Sample 2||Sample 3||Average|
|# Unpopped Kernels|
|# Unpopped Kernels|
Additionally, you can have the children make a hypothesis as to which one they think will score the highest and why. Providing an opportunity for the children to use the scientific method.
- Measure out 1 tablespoon of Sample 1 kernels.
- Count the # of kernels and record on your chart.
- Pop the popcorn kernels in the air popper or paper bag.
- Place the popped popcorn in the large and allow to cool.
- Using the 2-quart measuring cup, measure the sample of popped kernels and record the volume on the chart.
- Count the number of unpopped popcorn kernels and record them on the chart.
- Determine the shape of the popcorn kernels: mushroom or butterfly
- Using the ruler, measure the size of the popcorn kernels. Use the average of 3 popcorn pieces per sample.
- Repeat steps 2 through 9 with the other 2 samples from the white popcorn kernels.
- Repeat steps 3-8 with all 3 samples from yellow popcorn kernels.
- Take the average of the three tests for each popcorn and compare the observations.
You can introduce the topic of random variation and how that was reduced by repeating the test three times. The idea of a random variation will help explain why retesting an experiment is an important part of the scientific method.
Once all the data is collected, it is time to develop a conclusion based on the data collected. Here are a few questions to ask the children to help them analyze the data and determine their own conclusions.
- Which of the popcorn samples produced the largest popped pieces of popcorn?
- Which type of popcorn takes up more volume, yellow or white?
- Did the yellow and white kernels produce similar or different shapes?
- How do your results compare to other groups or classmates?
- Does your data support or disprove your hypothesis?
- Based on your data, what is your conclusion?
We hope that this experiment was fun and exciting. This popcorn experiment allows kids to take a deep dive experience into understanding independent and dependent variables.
Here are a couple of ideas of how you could take this experiment one step further.
- Weigh out 10g of kernels and count the number of kernels to determine the overall size.
- Use different colored kernels if they are accessible.
- Compare different popping methods with the same type of kernels.
- Have a discussion as to what other variables could be contributing to the results or what could be changed to make the experiment better.