I've been wondering the effect of $\ce{O2}$ on soap foam in a closed, test room. The room contains a candle and soap foam.

That is to say: if the room has lower and decreasing $\ce{O2}$ in its air, does the foam is effected (i.e., the soap produces lower foams)?

PS: I have very basic knowledge in Chemistry, and, excuse me if I didn't formalize the question in a good manner.


1 Answer 1


Hmmm. I don't know, but I'd say that if you significantly lowered the percentage of $\rm O_2$ in the air, the average molecular weight of the molecules in the bubble would drop (there'd be more low-molecular weight nitrogen and less higher-molecular weight oxygen), so the rate at which gas would diffuse out of the bubble would increase, and the foam would flatten faster.

Try blowing a foam with nitrogen, and compare it with the results of blowing a foam with air or oxygen---if I'm right, the foam blown with nitrogen will flatten a bit faster.

There'll be a bit more $\rm CO_2$ in the air from the candle, and that would diffuse more slowly out of the bubble (in fact, $\rm CO_2$ is used as a "blowing agent" to make foams, partially for that reason). But I'd think in this case that the small amount of $\rm CO_2$ produced by the candle would dissolve in the liquid, with gas dissolution rates enhanced by the lower surface tension and higher surface area of the foam.

  • $\begingroup$ "...foam would flatten faster.", by flatten you mean blowing-up faster? $\endgroup$ Jan 16, 2015 at 17:53
  • 1
    $\begingroup$ I mean the bubbles in the foam would probably shrink faster, because lower-molecular weight gas would leak out of them more quickly. $\endgroup$ Jan 16, 2015 at 17:55

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