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Re: [Phys-l] lab suggestion for teaching about the greenhouse effect?



I haven't tried this method of infusing CO2, but I want to try it (or get a student to do it). Calculate the mass of dry ice needed to overfill (about 5 g), 1/2 fill (about 1.8 g), 1/4 fill (about 0.9 g) a 2 L bottle (I assumed an air temp of about 300 K), and put that amount in and with the top off, let the dry ice sublimate. Because CO2 is denser than air, it will push air out the top and remain, for the most part in the bottom (don't take too long or diffusion will ruin this). Then cap the bottles. You still have varying water vapor contents, but you can calculate the relative fractions of water vapor from bottle to bottle because they will all start out with close to the same relative humidity, so the overfilled bottle will have no water vapor, 1/2 filled will have 1/2 the H20 vapor as 1/4 fill, etc. The cooling from the dry ice will make the outside of the bottle sweat, but that's vapor from outside air condensing.

Unfortunately, this isn't a realistic GW scenario because we aren't anywhere close to 25% CO2. A 2 centigrams of dry ice would fill about 0.5 % of the bottle, so getting reasonable modeling of the atmospheric content would be difficult. Still it would be interesting to compare the high fraction systems.

Also, a "real" greenhouse needs an absorber/re-emitter like dirt or rock. Try a set of bottles without dirt and set with dirt.

I wouldn't use carbonated beverage. Too little control.

-----Original Message-----
From: phys-l-bounces@carnot.physics.buffalo.edu [mailto:phys-l-bounces@carnot.physics.buffalo.edu] On Behalf Of John Denker
Sent: Saturday, February 12, 2011 9:55 AM
To: Forum for Physics Educators
Subject: Re: [Phys-l] lab suggestion for teaching about the greenhouse effect?

On 02/11/2011 02:59 PM, Fowler, Rebecca SHS Staff wrote:
Use two separate 2 L bottles. In one, place some carbonated cola poured
from a freshly opened bottle. In the second, place an identical volume
of cola that has gone nearly completely flat.


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