General Characteristics of Solids

Matter exists in three physical states -- solid, liquid and gas -- and of the three, solids are what we meet most often in daily life. What sets a solid apart is that, unlike a gas (whose molecules move randomly, hardly exerting any force on one another) or a liquid, a solid's atoms, ions or molecules are held together by strong forces of attraction into a definite, ordered arrangement. That ordering gives every solid five characteristic properties:

1. Definite volume and shape -- a solid does not flow to fill its container the way a liquid or gas does.
2. Rigid and incompressible -- applying pressure barely changes a solid's volume, because its particles are already packed close together.
3. Strong cohesive forces -- the attraction holding the constituent particles together is considerably stronger than in a liquid or gas.
4. Short interatomic, ionic or molecular distances -- the particles sit very close to one another compared with their spacing in a liquid or gas.
5. Fixed mean positions -- each constituent (atom, ion or molecule) is anchored to a particular spot in the structure and can only oscillate about that mean position; it cannot wander the way a liquid or gas particle can. …