Re: [asa] Easy to show experiments

George posted: "In One Two Three ... Infinity, pp.121-123, George Gamow
describes a experiment which shows (& allows you to calculate) the
minimum thickness of an oil film & thus implies the existence of a
minimum size of oil particles - molecules, of course, not "atoms" in
modern terminology. Briefly, get a pan of water completely level,
stretch a straight wire over it in contact with the surface & let a drop
of oil spread out on one side of the wire. Then slowly move the wire,
spreading out the oil, till the oil film breaks. You can see when this
happens by the change in reflected light intensity where the film has
broken. (The intensity from the oily part is less because of the change
in phase of the light at the oil-air interface relative to that reflected
at the lower surface of the oil film.)

It sounds simple in theory but I tried it once with no success. A cubic
mm would cover about a square meter & you'd would need a precisely level
surface & straight wire over a distance on the order of a meter. OTOH
I'm no experimentalist."

That would probably be an OK way, but since you could not make it happen,
I'm skeptical of using it. Too much apparatus.

From another source it was suggested that a water glass 1/2 full of water
and another water glass 1/2 full of sugar be prepared. When the sugar is
poured into the water the resulting mixture is not a full cup.

But since the sugar grains are not a tight fit, this does not seem to do
it either.

Burgy

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Received on Wed, 12 Sep 2007 09:19:57 -0600