|MadSci Network: Chemistry|
A gel is neither a liquid or a solid, but a mixture contains both liquid and solid mixed together. The solid part is a very fine, three-dimensional network, providing countless microscopic pores which are filled with liquid. This network is usually made up of very large molecules, like the proteins in gelatine, the modified starches in set yogurt or the polyvinyl alcohol in 'slime'.
You might have noticed with some of the gels mentioned above that over time liquid can ooze out from the gel, as the solid part packs closer together. Since the molecules in the network are only loosely bound together, it is possible to push them past each other with a little pressure and make a gel flow like a liquid; when the pressure is removed, the gel will sit there looking like a solid again.
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