Unfortunately, there are no generally accepted
definitions for 'ideal liquids' and 'ideal solids.' In most cases,
though, we can say that a liquid is something that can flow, and a
solid is something that will remain rigid unless you push on it. So
something like water is definitely a liquid since it changes its shape
by flowing into a container. But ice is definitely a solid since it
bends just a tiny bit, without flowing, until it actually breaks.
are, however, some cases (like the cornstarch/water mixture that you
mentioned) that don't quite fall into either category. That's why
everyone isn't quite agreed on these definitions.
actually answered a couple of questions talking about Non-Newtonian
fluids before and you can find them under the category 'Solids Liquids
and Gases: Liquids.' There is also a very interesting article that I
found called, 'Is glass liquid or solid?'
that talks a lot about what makes something a solid or a liquid or perhaps something in between. Check it out!
(republished on 07/25/06)