4E40.10 • Greenhouse Effect

Photo of the Demonstration at the University of Texas at Austin:

Faculty Notes:

• There are two chambers, one with valves and one without valves. The chamber with valves contains butane, and the chamber without valves contains air.
  • Check that the water-filled cuvette is inserted into the 7th hole from the left.
  • Place the air-filled chamber between the cuvette and thermopile, and measure the response from the thermopile with the voltmeter.
  • Replace the air-filled chamber with the butane-filled chamber, and measure the response from the thermopile.
  • Set the chambers aside. Now, replace the cuvette with black-metal disk. You can pour the cuvette out into a provided beaker. Let the disk heat up for 2-3 minutes, and then measure the response from each chamber again.

Concept Conveyed:

• Demonstrates the effect of greenhouse gases on the absorption of solar radiation.
• Radiation received from the Sun is demonstrated by short-wave infrared radiation that is attenuated by absorption in water and light from a lamp. Radiation emitted by the Earth is demonstrated by heating a black metal disc.
• This radiation passes through air / butane gas and reaches a thermopile. Comparing these two values, we see that this radiation is mostly absorbed by butane gas, making it the main source (greenhouse gas) heating up the atmosphere.

Demo Staff Notes:

• Insert light source into the leftmost hole of the wooden base.
• Fill the cuvette with water and insert it into the 7th hole from the left.
• Place the pegs for the gas-filled chambers in the 9th hole from the left and the 5th hole from the right.
• Insert the thermopile at the rightmost hole. Connect the thermopile to a voltmeter.
• If the plastic wrap that seals the chambers is broken, replace it with new plastic wrap. Now, find the chamber with valves. Turn both valves into the open position, and attach the silicone tubing to one valve. Turn the valve with the silicone tubing towards the ground and insert the nozzle of the butane canister into the free end of the tubing. Squeeze the nozzle through the tubing and depress the nozzle to release the butane
• Provide a small beaker with this demo so that the water in the cuvette can be poured out.
• Before storing the demo, take the butane-filled chamber outside, open both valves, and let the butane diffuse out for a minute or two. You can use a balloon pump to gently pump the butane out of the chamber.

Last updated on October 26, 2023