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Name: Lauren H.
Status: student
Age: 13
Location: N/A
Country: N/A
Date: 10/2/2004


Question:
If you put a gummy bear in water and let it sit there for about an hour or two, it will enlarge because it absorbs the water. Why is this?


Replies:
Substances in the gummy bear that give it solidity are: glucose, starch and gelatin. All of these substances can absorb (form some interaction with) water. However, while water can be absorbed, the starch and gelatin are prevented from dissolving in water. So the water swells the gummy bear rather than dissolves it.

Think of a very dry sponge such as used for washing dishes. In this form it is a small, hard material. However, it is porous and water can go into those pores. When water enters the pores, the sponge gets enlarged, and becomes flexible.

Greg (Roberto Gregorius)


That sounds like fun. I bet it gets really soft and flimsy too. Eventually, in enough water, it will all dissolve. Gummy bears are made of protein-gelatin, water, and sugar. It is just extra-thick "Jell-O". You can make similar yourself by with a Jell-O packet by cutting the water and added sugar by a factor of 2-4. instead of being wet and wiggly it comes out tougher and rubbery and able to get dry on the surface.

Or you can make Jell-O shapes and slowwwly dry them out, and watch them shrink over the course of a week or a month. It's exactly the opposite process of your water-swelling. Better to use sugar-free, keep it in a loosely covered in a transparent container, and maybe in the refrigerator so it cannot grow much mold or bacteria.

Think twice about eating it if it has been out of the refrigerator a long time.

The term "gel" are scientifically recognized as meaning: "a nano-scale webwork of solid substance filling only a small percentage of its apparent volume, the remainder being empty or filled with a fluid". (I am not quoting anybody, just made that up.) Gelatin is a gel in which the solid webwork is made of a certain bio-protein.

So, liquids and gasses can penetrate all parts of it, going into it and out of it at will, like wind through a jungle-gym, but slower. And if the webwork is flexible or stretchable, the shape can expand or contract in response to the change in fluid content. Some gels, made of glass or metal oxides rather than protein, are rigid instead of flexible.

But Gummy Bears are flexible.

Jim Swenson



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