The greenhouse effect in a bottle, and why the bottle model needs care

The idea

Carbon dioxide absorbs infrared radiation and warms the air, but a bottle mostly measures trapped convection, so the practical teaches both the effect and the limits of a physical model.

What you need

• two identical clear plastic 750 mL drinks bottles, each with a small hole drilled in the cap and a thermometer through it; caps must not be airtight (Earthlearningidea Greenhouse effect in a bottle)
• 250 mL of the same mixed tap water in each bottle, and two effervescent tablets for the carbon dioxide bottle
• an incandescent lamp placed equally close to both bottles, or direct sunlight
• the Earthlearningidea sheet and the American Journal of Physics analysis (Wagoner, Liu and Tobin 2010)

How to do it

1. Pour 250 mL of the same mixed tap water into each bottle, fit the caps with the thermometers clear of the water and record both starting air temperatures.
2. Add two effervescent tablets to one bottle and close it quickly; note the small temperature drop as the reaction absorbs heat.
3. Place the lamp equally close to both bottles and record both temperatures every 3 minutes for 15 minutes; repeat with the bottles swapped.
4. Plot both curves and report the difference at 15 minutes and its sign in each run.
5. Read the AJP analysis and list why the bottle does not reproduce the atmospheric greenhouse effect: carbon dioxide’s greater density suppresses convective mixing, and the radiative effect over a bottle’s short gas path is very small.
6. State what the bottle can show, what evidence (infrared absorption spectra, satellite measurements of outgoing radiation) shows the real mechanism, and how an argon-filled control bottle would separate the two effects.

What you should see

Earthlearningidea reports that the carbon dioxide bottle ends 2 to 4 °C warmer after 15 minutes, depending on the power of the bulb, after a small first drop because the tablet reaction is endothermic. Wagoner, Liu and Tobin (Am. J. Phys. 78, 536, 2010) show that in this kind of experiment the difference comes from carbon dioxide’s greater density suppressing convective mixing with the ambient air, not from infrared absorption, and that argon, close to carbon dioxide in density but with no infrared absorption, is the control that separates the two; the learner’s conclusion must keep the observed difference and its cause apart.

What changes

What you change

gas in the bottle (air or carbon dioxide)

What you measure

temperature rise after 15 minutes

What you keep the same

• bottle size and material
• lamp distance
• thermometer height
• starting temperature
• swapped positions between runs

Common misconceptions

Each of these ideas is wrong, and the activity is a chance to test it.

• A jar of carbon dioxide under a lamp proves the greenhouse effect.
• The greenhouse effect is the same as a garden greenhouse (a greenhouse mostly stops convection).

Safety card

Curriculum references

The NSW syllabus outcomes and Australian Curriculum v9 codes this activity supports. They are references, not a verified or complete curriculum alignment.

• Earth and Environmental Science Stage 6 Syllabus (2017), NESA; current, replaced by the 11–12 Syllabus (2025) from 2028EES12-14EES11/12-1EES11/12-6EES11/12-7
• Earth and Environmental Science 11–12 Syllabus (2025), NESA; to be implemented from 2028, not yet taughtEES-12-03
• Australian Curriculum v9No Australian Curriculum v9 code is listed.

Sources

The pages the author read to write this activity.

1. www.nsw.gov.au/education-and-training/nesa/curriculum/science/earth-and-environmental-science-stage-6-2017
2. www.earthlearningidea.com/PDF/441_Greenhouse_bottle.pdf
3. doi.org/10.1119/1.3322738