Why don't solids flow?

Answer 1

As a matter of fact, some solids flow, only they do it in very very long time or under stress. First we would need to define solid. A true solid has certain level of organization at molecular level, or crystallinity. Many solids have very ordered and stable organization, such as a diamond or quartz crystal. They most surely will never flow, but break appart under stress.
I haven't mentioned polymers, that's quite a different story.

Now, take a metal, such as copper or aluminum sheets. It is a true solid, because it forms crystals, however their intermolecular interactions are of different nature (See the crystallinity and the malleability articles at wikipedia). Normally it maintains its shape, but a sheet can be forced between a pair of stamp molds. It has been recognized that in such case, the malleable metal flows to aquire the mold figure due to the stress applied. The same with forging, drawing, extrusion, and other manufacturing processes. Also, a metal can be deformed very slowly when under a stress for a very long period. this is called "creep"
Moreover, it has been observed that stained glasses from very old churches are slightly thicker at the base than in the top, because the glass has flowed due to gravity for a thousand year. By the way, glass is not considered a true solid by the material scientist, but who cares, it IS a solid for ordinary mortals. So there you have it, some solids do flow.

Answer 2

because they are solid. seriously, that is part of the definition. A gas will fill a 3-dimensional container completely, a liquid will flow to fill a container like a bowl, but a solid maintains its form or shape when not restrained.

Answer 3

In a solid, the particles have little energy, and become tightly packed together. So, instead of being able to flow freely to the lowest possible level, they never separate.

Answer 4

All atoms are attracted to each other by Van der Waal forces. Gases and liquids contain enough energy to minimize these forces, so the atoms move more freely amongst each other. Solids, however, do not posses enough energy to override the forces, so the atoms tend to stay in the same positions in reference to each other.

Answer 5

Because the bonds holding the atoms together are to strong and organised, when they are heated i.e. to melting point the bonds are weaker and less organised until they finaly reach boiling point and than bonds are more or less totally dissolved and they become a formless gas.

Answer 6

Because one of the Definitions of a "Solid"- is that it doesn't have the Properties of "viscosity"- that a Liquid does.

Answer 7

The kinetic molecular structure is to strong for there to be enough movement to let it flow.