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Investigating Popcorn with the Ideal Gas Law (7 Favorites)

LESSON PLAN in Percent Composition, Ideal Gas. Last updated December 8, 2020.


Summary

In this lab, students will collect data to determine the pressure inside a popcorn kernel when it pops using the Ideal Gas Law. They will also calculate the percentage of water present in the average popcorn kernel. This resource includes two versions of the student activity, traditional and inquiry.

Grade Level

High School

NGSS Alignment

This lab will help prepare your students to meet the performance expectations in the following standards:

  • HS-PS1-7: Use mathematical representations to support the claim that atoms, and therefore mass, are conserved during a chemical reaction.
  • Scientific and Engineering Practices:
    • Asking Questions and Defining Problems
    • Using Mathematics and Computational Thinking
    • Analyzing and Interpreting Data
    • Planning and Carrying Out Investigations

Objectives

By the end of this lab, students should be able to:

  • Determine the percentage of water in popcorn.
  • Determine the moles of water in a popcorn kernel.
  • Use the ideal gas law to determine the pressure inside a popcorn kernel when it pops.

Chemistry Topics

This lab supports students’ understanding of:

  • Ideal Gas Law
  • Percent Composition
  • Unit Conversion

Time

Teacher Preparation: 30 minutes
Lesson: 45–60 minutes

Materials

  • Popcorn kernels, 1 bag
  • Electronic balance, 1 per group
  • Weighing boat or paper towel, 1 per group
  • Graduated Cylinder, 10-mL, 1 per group
  • Cooking oil
  • Beaker to hold cooking oil
  • Pipette to distribute cooking oil
  • Erlenmeyer Flask or beaker, 250-mL, 1 per group
  • Aluminum foil, precut squares, 1 per group
  • Hotplate, 1 per group
  • Beaker or crucible tongs, 1 per group
  • Paper towels, several per group

Safety

  • Always wear safety goggles when performing experiments in the lab.
  • Exercise caution when using a heat source. Hot plates should be turned off and unplugged as soon as they are no longer needed.
  • Heat flask/beaker evenly to prevent oil from spattering. Boiling oil is hotter than boiling water.
  • Food in the lab should be considered a chemical not for consumption.
  • Wash the flask/beaker in soapy water, rinse, and dry when you have finished the lab.
  • Students should wash their hands thoroughly before leaving the lab.

Teacher Notes

  • This resource includes two versions of the student activity. The first is a traditional lab that includes complete instructions for students. The second is an inquiry version of the lab that requires students to read information and then plan what data that they need to collect to determine the pressure inside the kernel when it pops and also to determine the percent of water in each kernel.
Type of OilBP
Safflower510°F
Soybean495°F
Corn475°F
Peanut440°F
Olive375°F
  • Use these guidelines and assumptions to help your students perform the lab and collect the data:
    • Assume that the temperature inside each popcorn kernel is the same as the temperature of the boiling point of the oil that is used. The table on the right shows boiling point data from the Department of Physics at the University of Illinois at Urbana-Champagne.
    • Assume that the moles of water used in the Ideal Gas Law equation is equal to the moles of water in each kernel. Each lab group should use 25 popcorn kernels to calculate the average mass of one kernel. They then compare the mass of the flask/beaker, oil, and popcorn before and after popping to find the total mass of water lost during popping. This is used to calculate the average mass and moles of water per kernel.
    • Assume that the volume used in the Ideal Gas Law equation is equal to the average volume of a popcorn kernel. Students use the kernels and water displacement in a 10-mL graduated cylinder to determine an average volume for each kernel.
    • After collecting this data, students should discard the kernels that they used get 25 fresh kernels to pop.
    • To pop the kernels, students pipette enough cooking oil into a 250-mL Erlenmeyer flask or beaker to coat the bottom, add the kernels and measure the mass. They then cover the top of the flask or beaker with a piece of foil and poke it to make several holes to allow the steam to escape. They then gently pop the kernels with a hotplate set to medium heat. It is important that they use beaker or crucible tongs to swirl the flask/beaker on the hotplate to ensure even heating.
  • If you plan to do this lab with your classes year after year, you might consider having a set of beakers/flasks specifically for this activity.
  • For an extension activity, ask students to compare the water content of different types or brands of popcorn or investigate the difference in popping with different types of oil.

For the Student - Traditional Lab

Background

Popcorn is one of our favorite snacks! Who can sit through a movie without a big tub of buttered corn? And what would Halloween be like without popcorn balls or Christmas without popcorn strings on the tree and the big cans of caramel and cheese popcorn? Have you ever wondered what makes hard corn kernels “pop”? There are many different varieties of corn and each contains different amounts a starch, water and sugar. When popcorn kernels are heated in hot oil on the stove or in the microwave, the water trapped inside the hard shell begins to boil and vaporize. Eventually, the pressure inside the kernel causes it to pop open and fluff up. When that happens, the water in the kernel escapes as a gas, leaving only the corn behind.

Objective

What is the pressure inside a kernel of popcorn? What is the percent water present in the average kernel when it pops? You will take lab measurements before and after popping the corn to help you answer these questions.

Equipment

  • Popcorn kernels
  • Electronic balance
  • Weighing boats
  • Graduated Cylinders, 10-mL
  • Cooking oil
  • Beakers
  • Pipettes 
  • Erlenmeyer Flasks or Beakers, 250-mL
  • Aluminum foil squares
  • Hotplates
  • Beaker or crucible tongs
  • Paper towels

Safety

  • Always wear safety goggles when performing experiments in the lab.
  • Exercise caution when using a heat source. Hot plates should be turned off and unplugged as soon as they are no longer needed.
  • Heat flask/beaker evenly to prevent the oil from spattering. Boiling oil is hotter than boiling water.
  • Food in the lab should be considered a chemical not for consumption.
  • Wash flask/beaker in soapy water, rinse, and dry.
  • Wash your hands thoroughly before leaving the lab.
Type of Cooking OilBP
Safflower510°F
Soybean495°F
Corn475°F
Peanut440°F
Olive375°F

Procedure

Part 1: Collecting Data

  1. Assume that the temperature inside each popcorn kernel is the same as the boiling point of the oil that is used. The table shows boiling point data from the Department of Physics at the University of Illinois at Urbana-Champagne.
  2. Use a weighing boat and scale determine the mass of 25 popcorn kernels. Record the mass in the data table below.
  3. Assume that the volume used in the Ideal Gas Law is equal to the volume of one kernel. Add about 5 mL of water to a 10-mL graduated cylinder. Record exact volume in the data table below. Then, add the 25 kernels of popcorn and record the volume.
  4. Discard the 25 kernels of popcorn and wash out the graduated cylinder.

Part 2: Popping Corn

  1. Get 25 fresh popcorn kernels.
  2. Cover the bottom of a dry Erlenmeyer flask/beaker with cooking oil using a pipette.
  3. Add the popcorn.
  4. Record the mass of the flask/beaker, popcorn, and oil.
  5. Cover the top of the flask/beaker with aluminum foil and poke several holes so that the water vapor can escape.
  6. Use a hotplate set on medium heat to pop the corn, slowly swirling the flask/beaker around with tongs to avoid burning it.
  7. IF THE POPCORN BURNS YOU MUST START OVER!
  8. Remove the flask/beaker from heat when the kernels have popped. 
  9. Carefully remove the foil and use a paper towel to dry any water from the top of the flask/beaker.
  10. Be careful when using the hotplate and turn it off and unplug it when you are finished using it.
  11. Let the flask/beaker cool.
  12. Pour popcorn onto a clean paper towel and count the number of unpopped kernels. Since they did not pop, the water inside them was not released and will not be considered in your calculation of the mass and moles of water in the kernels.

Data

(Don’t forget your units)

Temp.

What type of cooking oil did you use?
What is the boiling point of your cooking oil?

Kernel Mass

Mass of empty weighing boat
Mass of weighing boat after adding popcorn.
Number of popcorn kernels

Volume

Initial volume of water (before adding popcorn)
Final volume of water (after adding popcorn)
Number of popcorn kernels

Water Mass

Mass of empty Erlenmeyer Flask/Beaker
Mass of Erlenmeyer Flask/Beaker, popcorn, and oil
Number of popcorn kernels used
Mass of Erlenmeyer Flask/Beaker and popped corn
Number of unpopped kernels

Calculations

(show your work for each section in the space provided)

1. Average mass of ONE popcorn kernel in GRAMS:
2. Average volume of ONE popcorn kernel in LITERS:
3. Total mass of water in all popped kernels in GRAMS:
4. Average mass of water in one popped kernel in GRAMS:
5. Average moles of water in one popped kernel:
6. Percent of water in each popped kernel:
7. Convert temperature to Kelvin
8. Pressure inside the kernel at the time of the “POP” (Use the Ideal Gas Law):
9. Name and explain one potential source of error.

For the Student - Inquiry Version

Background

Popcorn is one of our favorite snacks! Who can sit through a movie without a big tub of buttered corn? And what would Halloween be like without popcorn balls or Christmas without popcorn strings on the tree and the big cans of caramel and cheese popcorn? Have you ever wondered what makes hard corn kernels “pop”? There are many different varieties of corn and each contains different amounts a starch, water and sugar. When popcorn kernels are heated in hot oil on the stove or in the microwave, the water trapped inside the hard shell begins to boil and vaporize. Eventually, the pressure inside the kernel causes it to pop open and fluff up. When that happens, the water in the kernel escapes as a gas, leaving only the corn behind.

Objective

What is the pressure inside a kernel of popcorn? What is the percent water present in the average kernel when it pops? You will take lab measurements before and after popping the corn to help you answer these questions.

Available Equipment

  • Popcorn kernels
  • Electronic balance
  • Weighing boats
  • Graduated Cylinders, 10-mL
  • Cooking oil
  • Beakers
  • Pipettes 
  • Erlenmeyer Flasks or Beakers, 250-mL
  • Aluminum foil squares
  • Hotplates
  • Beaker or crucible tongs
  • Paper towels

Safety

  • Always wear safety goggles when performing experiments in the lab.
  • Exercise caution when using a heat source. Hot plates should be turned off and unplugged as soon as they are no longer needed.
  • Heat flask/beaker evenly to prevent the oil from spattering. Boiling oil is hotter than boiling water.
  • Food in the lab should be considered a chemical not for consumption.
  • Wash flask/beaker in soapy water, rinse, and dry.
  • Wash your hands thoroughly before leaving the lab.
Type of Cooking OilBP
Safflower510°F
Soybean495°F
Corn475°F
Peanut440°F
Olive375°F

Prelab Questions

You will collect data to determine the pressure inside the kernel when it pops using the Ideal Gas Law (PV = nRT) and calculate the percent of water present in the average popcorn kernel. Read through the lab and determine what measurements to take to collect data that will allow you to make these two calculations.

  1. You can assume that the temperature inside each popcorn kernel is the same as the boiling point of the oil that is used. The table shows boiling point data from the Department of Physics at the University of Illinois at Urbana-Champagne. What cooking oil is your group using and what temperature is the kernel as it pops? Convert the temperature to Kelvin to use with the Ideal Gas Law.
  2. You can also assume that the moles of water used in the Ideal Gas Laws equation is equal to the moles of water in each kernel. Get the mass of 25 popcorn kernels to calculate the average mass of one kernel. But that’s the total mass of a kernel, how will you figure out the mass of the water? Describe the measurements you will take to determine the mass of the water in one kernel.
  3. What equipment will you use to take your mass data?
  4. Unfortunately, you can’t use mass in the ideal gas law. What conversion do you need to use to make your data usable?
  5. How will you calculate the percentage of water in a kernel of popcorn?
  6. Assume that the volume used in the Ideal Gas Law is equal to the volume of one kernel. Describe how you can determine that value using a 10-mL graduated cylinder and water.
  7. What equipment will you use to collect the volume data?
  8. You can’t use milliliters in the Ideal Gas Law. What conversion do you need to make your data usable?

Procedure for Popping Corn

After collecting mass and volume data following the procedures you outlined in the prelab, it’s time to pop some corn! Follow these steps, keeping in mind that if the popcorn burns, you will need to start over.

  1. Get the same number of popcorn kernels to pop as you used to collect your data.
  2. Cover the bottom of a dry Erlenmeyer flask/beaker with cooking oil and add the popcorn.
  3. Cover the top of the flask/beaker with aluminum foil and poke several holes so that the water vapor can escape.
  4. Use a hotplate to pop the corn, slowly swirling the flask/beaker around with tongs to avoid burning it. 
  5. Remove the flask/beaker from heat when the kernels have popped. 
  6. Carefully remove the foil and use a paper towel to dry any water from the top of the flask/beaker.
  7. Be careful when using the hotplate and turn it off and unplug is when you are finished using it.
  8. Let the flask/beaker cool.
  9. Pour popcorn onto clean paper towel and count the number of unpopped kernels. You will want to make sure to consider these in your final calculations.

Data Collection and Calculations

Use the procedures you outlined in the prelab questions to collect date to calculate the following values. Indicate the data collected and calculations used for each variable.

Temperature from prelab Unpopped kernels
Mass of Water in One Popcorn Kernel Data Calculation
Volume of One Popcorn Kernel Data Calculation
Moles of Water in One Popcorn Kernel Data Calculation
Pressure in a Popcorn Kernel as it Pops Calculation
Percent of Water  in a Popcorn Kernel Data Calculation
Name and explain one potential source of error.