Post by Bruce SinclairPost by N:dlzc D:aol T:com (dlzc)Post by sydsciencePost by sydscienceMy daughter did her science experiment measuring the
deflation rates of latex balloons filled with helium, carbon
dioxide and compressed air. The carbon dioxide balloons
deflated fastest but we have no idea why.
http://www.answerbag.com/q_view/734234
Post by sydsciencePost by sydscienceDoes anyone know the reason that carbon dioxide filled
balloons deflate faster than helium or compressed air?
Many thanks.
No reason for this to happen that I know of. How did
you decide rates of deflaton?
We measured the circumference of the balloons
every 30 minutes.
My guess is there is something funny in how you got your carbon
dioxide. Maybe it was hotter than the other gasses, and cooling
added to an *apparent* deflation. How many balloon of each gas?
Most rubbers (and many plastics IIRC ?) are more permeable to CO2. Example
.. you inflate your car tyres with air. Tyre manufacturers recomend
nitrogen. After a while of filling them with air, you pretty much have 100 %
N. :)
Why ? The CO2 and O (slower I think ?) escapes faster. Why ? Perhaps it
'dissolves' in the rubber then permeates ?
I'm sure someone can confirm/deny :)
I can't confirm, but I can offer a related observation. I often
inflate hydrogen balloons for my chemistry class. Regular latex
balloons hold hydrogen gas just fine, at least for an hour or two.
One day, I was looking for another gas and got the bright idea to try
the house natural gas (which the bunsen burners usually run on). I
simply could not get the latex balloons to inflate, and I smelled
gas. Clearly, they were much more permeable to methane etc.. It
wasn't CO2, but it at least seems reasonable to me that chemically
selective permeability of the balloon might be an issue. In other
words, the size and/or molar mass of the gas may not be the only factor
(s) affecting its rate of diffusion out of the balloon. Perhaps Mylar
might be worth a try as a comparison?
- Craig
Permeability of gases through plastics films is a complex topic. One of the
"rules of thumb" is that increased solubility of the gas in a plastic is
likely to mean inceased permeation rate. Since "like dissolves like", the
solubility is likely to increase from He to CO2, to methane.
Ernie