We are all familiar with solids, liquids and gases. Whether a substance
is a solid, liquid or gas depends on the potential energy in the atomic
forces holding the particles together and the thermal energy of the
particle motions. The pressure on the subtance also has an effect on the
phase.
Solids
Crystaline Solids
Crystaline solids are characterised by a long-range order. The atoms
are closely packed on lattice points held in in place by atomic bonds.
The internal energy of the atoms is not sufficient to allow the atoms to
break away from their lattice positions. Examples of crystaline solids
include semiconductors, quartz, salt, etc.
Amorphous Solids
Amorphous Solids are still closely packed together but lack the
translational symmetry of crystaline solids. However, even amorphous
solids have relatively good spatial ordering, especially over small
distances, (10-100 molecules)
Liquids
As the material is heated, the internal energy is increased and the
atoms are no longer tied to their lattice positions but can move
relative to each other although the atoms are still closely packed
together.
Gases
A gas is matter in which the molecules are widely separated, move
around freely, and move at high speeds. Examples of solids include the
gases we breathe (nitrogen, oxygen, and others), the helium in balloons,
and steam (water vapor).
Plasmas
Eventually, given enough heat, the electrons and nucleus become
separated and into positively, charged ions and negatively charged
electrons. This soup of ions and electrons is known as a plasma
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