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



Hello Becky,
Try using a compressed gas "duster" that contains difluoroethane. Better
yet if you can find one of these products that contains tetrafluoroethane.
These are more efficient than CO2 at increasing the temperature inside the
soda bottle closed system. Try to spray the compressed gas for at least 10
to 15 seconds to concentrate it inside the bottle.

Also, there may be safety regulations at your school regarding student use
of these products, because of the danger of "huffing" or inhaling the
gas. Check with the administration before letting studens use the products.
Or, ou could do it as a demonstration activity.

I hope this helps,

Elizabeth Kennedy
Roseville, CA

On Fri, Feb 11, 2011 at 1:59 PM, Fowler, Rebecca SHS Staff <
FowlerR@issaquah.wednet.edu> wrote:

Hello,

I teach IB Physics, and am currently working through a unit on energy
and climate change. I would be interested in hearing from anyone who
has some ideas for easily and clearly demonstrating the greenhouse
effect. I have attempted to do the following lab with my students, but
with mixed results:

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. Place a stopper with a
temperature sensor into the top of each bottle, then place the bottles
in front of a heat lamp. Track the temperature changes in the bottle
with little additional CO2 being added to the atmosphere compared with
the changes in temperature in the bottle with significant additional CO2
being added to the atmosphere.

The results that, theoretically, we should get would show that the
additional CO2 would increase the air temperature faster than if there
isn't additional CO2. My most recent results, however, showed the
opposite (for all 8 lab groups!). Does anyone have any suggestions for
improving this activity, or doing something different, yet similar,
which will allow me to run a lab that demonstrates how additional
greenhouse gases in the atmosphere will impact the temperatures of the
atmosphere?

Thanks very much!

Becky Fowler
Sammamish, WA



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