Greenhouse in a Beaker

Activity Source: 

Adapted with permission by The NEED Project.

Carbon is naturally found in the atmosphere. Carbon dioxide, or CO2, itself is not considered a pollutant. The CO2 being released from burning fossil fuels was part of the atmosphere hundreds of millions of years ago before being captured by plants and sea organisms.

Carbon atoms naturally cycle through the biosphere, the atmosphere, the hydrosphere, and the lithosphere in process known as the carbon cycle. In the carbon cycle, carbon is exchanged at differing rates among these different spheres or reservoirs. Fossil fuels act as a carbon sinkto absorb carbon as it is released from different parts of the cycle. Burning these fossil fuels, however, adds carbon to the atmosphere faster than it can be removed naturally.

What effect does this have on our atmosphere? This activity helps students to understand the greenhouse effect and how carbon dioxide and thermal energy (heat) are related. For more information or other activities such as the Carbon Cycle Game, download NEED’s Exploring Climate Change guide from


  • 2 600 mL beakers
  • 1 250 mL flask
  • 1 rubber stopper with hole
  • 1 60 cm length of vinyl tubing (3/16” diameter)
  • 1 clip light
  • 1 1000-1100 lumen bulb (75-watt incandescent equivalent)
  • 1 ruler
  • 2 thermometers
  • Masking tape
  • 4 Alka-Seltzer® tablets
  • Safety glasses
  • Water


  1. Wear safety glasses. Set up the lamp 15 cm in front of the two beakers, so they receive equal light.
  2. Thread the tubing through the hole on the stopper. Insert the tubing through the hole in the flask. Do not secure the stopper into the top of the flask yet.
  3. Place the other end of the tubing near the bottom of one of the beakers. Secure the tubing inside the beaker using a small piece of tape. One beaker will have nothing added to it.
  4. Add 120 mL of water to the flask.
  5. Turn on the clip light. Wait for the temperature in each beaker to stabilize. The temperatures in the beakers should be similar but do not need to be identical.
  6. Record the stable temperature of each beaker.
  7. Break two Alka-Seltzer® tablets in half and drop the pieces into the flask. Secure the rubber stopper to seal the flask.
  8. Record the temperature in each beaker every 30 seconds for a total of 3-4 minutes.
  9. How does are carbon dioxide and thermal energy related? Cite evidence from your results in your explanation.
  10. If carbon dioxide can be stored and moved naturally through the carbon cycle, explain how the addition of too much CO2 to the system could have a negative impact.
  11. Extension: The activity above simulates the greenhouse effect during the day. Create an experiment to showcase this effect at night.