"Constantine" <[Only registered users see links. ].uk> wrote in message
news:bksbha$uub$[Only registered users see links. ].ac.uk...
There ya go again: Too brief and to the point. Can't cha tell me a little
about how it diffuses?
"Donald G. Shead" <[Only registered users see links. ]> wrote in message
news:0oicb.1823$[Only registered users see links. ].prodigy.com ...
OK, suppose that you leave a bottle with some perfume open in your house.
Sooner or later, you will smell it at the other end of the house, right?
What happens is that part of the perfume evaporates. That includes molecules
of alcohol and whatever else makes the perfume. If the bottle was closed,
this vapour would stay inside and right on top of the liquid perfume. But
the bottle is open, the molecules of the vapour are in a Brownian motion,
they mix with the molecules of the air (which are also in a state of
Brownian motion!) and eventually are carried away from the bottle. That's
what diffusion means. Now, the density of the perfume's vapour decreases the
further you are from the bottle. Yet, even a few molecules, are sufficient
to interact with your nose and thus you can detect it (i.e., smell it!).
It is the same phenomenon with diffusion of ink in water. Take a big jar of
water (transparent, so you can see what goes on inside) and drop a small
amount of ink. Then you will see how the ink diffuses in the water.
Unfortunately, I don't have handy a book of physics around me, so that I can
give you further references and/or a mathematical description.