Re: gummy bears

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From: Karen Kalumuck (karenk@exploratorium.edu)
Date: Thu Mar 06 2003 - 13:56:22 PST 

Message-Id: <v01540b06ba8d721ce41a@[192.168.111.144]>
Date: Thu, 6 Mar 2003 13:56:22 -0800
From: karenk@exploratorium.edu (Karen Kalumuck)
Subject: Re:  gummy bears

Hello Anita -

In the strictest definition of the term, osmosis is "the diffusion of water
across a semipermeable membrane". Diffusion is the movement of molecules
or particles from an area of high concentration to an area of low
concentration, and is due to the spontaneous, random motion of the
molecules or particles.

That said, technically the gummy bear experiment isn't osmosis, because
there is no membrane involved (I suppose the sugar/protein lattice that
forms the exterior of the gummy bear could be considered somewhat
membrane-like, but is not a true membrane). A more precise way to describe
the phenomenon may indeed be the diffusion of water.

I don't know how much "free" (not tightly bound to other molecules) water a
gummy bear contains. Only the "free" water can participate in osmosis, or
the diffusion of water. If the concentration of water in your salt
solution is lower than that of the free water in the gummy bear, water
should move out of the gummy bear into the solution. I would try burying
the gummy bears in dry salt as a starting point.

Let us know what happens!

---Karen Kalumuck

Karen E. Kalumuck, Ph.D.
Biologist/Educator
Exploratorium Teacher Institute
3601 Lyon St.
San Francisco, CA 94123
415-561-0388
FAX 415-561-0307

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