Going back a couple of days to the seemingly puzzling phenomenon of water
and oxygen going out through stomata, while CO2 is going in, the key, as
Bill Williams mentioned, is that the molecules are very far apart and don't
interact much at all.
You can experience a similar situation if you have one odor (chopping
onions, for instance) being generated in one end of the kitchen while a
different one (coffee brewing) is diffusing from the other end. Although
both odors are strongest near the source, they both diffuse all the way
across the kitchen to the other end. No problem.
You could simulate this in a classroom by pouring some vanilla on a paper
towel in one corner and peppermint extract on a paper towel in the opposite
corner. As mint is known to increase mental alertness, it might be a useful
demonstration in a class where photosynthetic gas exchange was being
discussed. Keep 'em awake, anyway--and they're both plant products. It
would also get the idea of diffusion (as opposed to huffing and puffing)
Truth comes out of error more readily than out of confusion.
-- Francis Bacon (1561-1626)
Virginia Berg (bergv at uni.edu)
Biology Department 0421
University of Northern Iowa
Cedar Falls, IA 50614
(319) 273-2770 (phone), 273-2893 (fax)