Illustration of a thermometer next to Earth.
Teacher Guide

CO2 and our climate

Eunice Newton Foote & her groundbreaking discovery

This is the teacher guide for this lesson. A student-focused guide to assist learners as they perform the activity is available.

View the student guide: CO2 and our climate

What is CO2, and how does it affect the climate? How does CO2 compare to air as a greenhouse gas? How does CO2 in the atmosphere interact with infrared light (heat)?

  • 2 clear plastic bottles or jars (same size, with lids if possible)
  • 2 thermometers (standard classroom or digital)
  • Heat lamp
  • 5 g Baking soda (about a teaspoon)
  • 60 ml vinegar (about ¼ cup)
  • Balloon
  • Timer or stopwatch
  • Printed student guides

Students will use common materials to recreate Eunice Foote’s 1856 experiment, comparing how air and carbon dioxide respond to light exposure. Students will observe differences in temperature and develop an understanding of how carbon dioxide absorbs and responds to light exposure. Students will also observe how carbon dioxide retains heat, which can affect the climate. Teachers can use this Critical Conversations Guide (CCG) after the lesson to facilitate a discussion about how human actions and personal values connect to heat absorption and climate change.

  • Total time
    30 minutes
  • Education level
    Grades 6 - 10
  • Content Area
    Climate physics
  • Educational topic
    Climate change effects, energy transfer, gas properties, experimental method

In 1856, American scientist Eunice Foote conducted one of the earliest experiments to demonstrate the heat retention of CO2. Using simple glass cylinders, thermometers, and sunlight, she showed that air containing CO2 and water vapor heated more quickly and retained heat longer than dry air or air without CO2, providing an early experimental foundation for what would later become the theory of the greenhouse effect. Foote concluded that “an atmosphere of that gas would give to our Earth a high temperature.”

The experiment in this activity reproduces Foote’s setup using accessible materials such as plastic bottles, thermometers, and baking soda and vinegar to produce CO₂ gas. By comparing how quickly two sealed bottles warm under the same light source, one filled with air and the other with CO₂, students can directly observe the heat-trapping effect of greenhouse gases.

This demonstration offers a clear, hands-on example of radiative transfer: visible light energy entering a system, converting to heat, and interacting differently with various gases. Students will learn that CO₂ molecules absorb and re-emit infrared radiation, while air (mostly nitrogen and oxygen) does not.

Responses to common questions:

“Why can’t we just block sunlight to stop global warming?”

Because sunlight is essential for life. The issue is the trapping of infrared radiation by excess greenhouse gases.

“Could the CO2 be getting hotter because the light is somehow brighter?”

Stronger light might make the CO2 bottle even hotter, but the key factor is gas composition, not light intensity. More CO2 increases heat retention even under the same light conditions.

“Why is this called the greenhouse effect?”

This concept is similar to the greenhouse where plants grow. Both trap heat but physical greenhouses mainly retain heat by preventing air circulation, while the atmospheric situation involves infrared absorption by gases.

“Are there other gases that also trap heat?”

Yes, other gases like methane (CH4) or water vapor (H2O) are also greenhouse gases that work other than CO2 but CO2 is the easiest to use in the classroom.

“Are there any natural sources of CO2?”

Yes – volcanic eruptions, animals breathing out, fires, and decomposition are all examples. But these aren’t as prevalent as human sources of CO2 – burning coal/oil, industrial manufacturing, farms, and deforestation.

Key terms
  • Carbon dioxide (CO2)A colorless gas that absorbs infrared radiation, contributing to the greenhouse phenomena.
  • AbsorptionThe process by which matter takes in energy from light or heat.
  • Infrared radiation/infrared radiationA type of electromagnetic radiation with wavelengths longer than visible light that carries heat energy. Emitted by objects as heat, allowing us to measure the temperature of an object.
  • Radiative transferThe movement of energy as electromagnetic radiation is emitted, absorbed, or transmitted through a medium.
  • TemperatureA measure of the average kinetic energy of the particles in a substance.
  • EnergyThe ability to cause change in a system, or the ability to do work. This experiment uses energy from light transformed into heat.
Before the experiment

This is intended as a teacher demonstration with student involvement, but can be done by student groups if materials allow. We invite you to watch a brief video demonstration of the developer conducting the experiment you’ll be facilitating with your students. Showing the first 1.5 minutes of the demonstration video to students may help review and solidify the concepts they discovered in Activity 1.

Setting up

  • Make sure every student has a copy of the student guide.

  • Pose the driving questions, along with the brainstorming question.

  • Allow students to brainstorm ways that they might measure heat retention in CO2 versus air.

  • Introduce students to Eunice Foote. Consider exploring her scientist profile and historical significance using short biographical videos or reading excerpts from “Eunice Foote and the Greenhouse Gas Effect”.

  • Prepare the bottles in front of students (have them volunteer for different steps as you see fit).

    1. Label one bottle “Air” and the other “CO2”
    2. For the CO2 bottle: combine about a teaspoon of baking soda with about ¼ cup of vinegar in the flask.
      • If students are completing this in groups, emphasize safe handling. Vinegar is not toxic, but can be harsh on the skin.
    3. Quickly attach the balloon to the mouth of the flask and let it fill up with CO2.
    4. Once full, pinch the balloon to capture the CO2 and remove from mouth of bottle.
    5. Direct the loose end of the balloon into the mouth of the test bottle and let the CO2 release into the test bottle.
      • Ensure bottles are not sealed too tightly after CO2 generation to avoid pressure buildup.
      • Teachable moment: Ask students why the CO2 replaces the air in the bottle (CO2 is roughly 1.5 to 1.7 times denser than air).
    6. Seal the bottle with the thermometer to trap CO2 inside.
    7. The air bottle should remain open to the room air. Seal right after sealing the CO2 bottle.
    8. Place one thermometer inside each bottle with the sensor tip visible.
    9. Check Setup:
      • Make sure both thermometers read similar initial temperatures.
      • Place both bottles the same distance from the lamp or light source. Keep the setup stable so that the light source heats both bottles equally.
During the experiment
Make a hypothesis

  • Based on their background discussion, students should make a prediction about what they expect will happen when both bottles are exposed to light:

    1. Which bottle do you expect to heat up faster? Why?
    2. Why might the composition of the gas make a difference?

  • Have them record their hypotheses on their students' guide. Have them discuss with another set of students.

Test your hypothesis

  • Begin the Trial: Turn on the light and start the timer. Students will record the temperature of both bottles every minute for 10 minutes. Call different students up to make the measurements each time.

  • Graph data: Students may begin plotting their data as they record it (Temperature vs Time for both bottles).

  • Optional: After turning off the light, have students continue to measure temperatures for 3-5 more minutes to see how quickly each bottle cools.

Answer Key: The students should observe that the CO2 bottle heats up faster and reaches a higher final temperature than the air bottle when exposed to the same light. This happens because carbon dioxide absorbs and retains infrared radiation, while regular air (which consists mostly of nitrogen and oxygen) does not.

After turning off the lamp, the CO2 bottle will also cool more slowly, showing that it holds heat longer. This is a direct demonstration of the greenhouse phenomena that Eunice Foote first described.


Discussion and conclusion

Choose any or all of the discussion and conclusion prompts below. We’re aware that climate change can bring up a variety of perspectives and emotions in the classroom – see our Critical Conversations Guide for tips on how to facilitate an open dialogue surrounding these issues.

    1. Have the students' conclusions start by relating back to their hypothesis. Did their evidence support or refute their hypothesis?
      1. If they were right, they should then be able to explain what causes the differences in temperature and how it can relate to the climate.
      2. If the results did not follow their hypothesis, then was their hypothesis wrong or were there errors in the experiment that could be improved on the next run?
      3. Ask students what would happen when we remove all the CO2 in the atmosphere. Would our climate remain the same?
        1. Answer: We see that an increase in CO2 will increase the temperature. Since CO2 traps heat, if we remove CO2 from our atmosphere entirely, our temperatures would drastically drop. During the night, it would become extremely cold, as the only heating would come from heat retained by the ground (which wouldn’t last very long).

  • Have students predict, using evidence from their experiment and the simulation, what will happen as more carbon dioxide gets added to the atmosphere.

  • Help students draw a connection between the Earth’s surfaces absorbing and reflecting incoming light as infrared radiation, and CO2 retaining and scattering that IR radiation, leading to the heating of the planet.

  • Ask students where they think the increase of is CO2 is coming from.

  • This video does a great job of summarizing the experiments, Eunice Newton Foote’s experiment, and the physics behind what the students observe. If time allows, show students the video and have them point out new and validating information as compared to what they saw.

Real-world connections

Credits

Developed by: Angella Johnson, Mahmoud Hallack, Sharanya Palit, Henry Tan, Jiayu Wang – Brown University

Piloted by: Thomas Binninger, Jacqueline Clarke, Nataliya Fletcher, Sandy Gady, Erin Martin, Vilma Orduna, Amy Truemper

Edited by: Rosie Durland – University of Utah

PhysicsQuest ©️ 2026 by American Physical Society is licensed under CC BY-NC 4.0

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