Re: If a liquid has no definite shape, and a solid does, then what is flour?

Erika,
     Flour is actually a solid.  Flour, like salt, is a collection of many 
smaller solid particles.  These particles are very small, and can act like 
a fluid in some sense of the word.  Try using a microscope, or magnifying 
glass to look at flour.  You should find that you are actually looking at a  
large number of small particles.
     An easy way to show that flour is a solid, and not a liquid, is to 
pour some water onto a table top.  It tries to take the shape of its 
container (the table top), and therefore spreads over the table surface.  
Now, pour some flour onto the (dry) table top.  It will hold some shape by 
forming a pile, and not spreading over the table surface like the water 
did.  This is not behavior typical of a liquid.
     The flour forms a pile because of the structure of its particles.  You 
can think of the particles composing the flour as small blocks.  These 
blocks stack on top of one another and form stacks of flour particles.
     For a good comparison, find a chemistry book and look up salt, NaCl.  
Salt has a crystalline structure, which causes it to form piles when 
spilled.  The chemistry book will give you a little insight as to the 
shapes and sizes of these particles that form the salt.
     A good question.  Always remember, before calling something a liquid 
or solid, be sure that it has the correct properties.

Hope this helps,

Randy