PHASES OF MATTER Solids, liquids and gases.

THE STATES OF MATTER
The states of matter arise due to the competion between thermal energy and the energy which binds molecules together as a result of intermolecular foreces.

GASES
If the thermal energy of a molecule is greater than its binding energy, then it can escape from a cluster of neighbours ; thus it is a gas. Molecular separation in a gas at S.T.P. is in the order of 10 times the separation at absolute zero. Gas molecules move about randomly and hence have no permanent order.

LIQUIDS
If the thermal energy of a molecule is close enogh to its binding energy that when under the attraction of another molecule it can leave its immediate neighbours and be captured by the molecule, then it is a liquid. The liquid state is not as clear cut as either the gas or solid state. The mean molecular separation between adjacent molecules is larger than in a solid., but is still of the same order as at absolute zero. Volume is constant.

SOLIDS
If the thermal energy of a molecule is less than its binding energy, such that it is not able to escape the attraction of its neighbours it is a solid. The mean molecular separation is of the same order as that at absolute zero. Volume is constant.

There are 3 main different types of solid

Crystalline Amorphous Polymerics

Example Diamond Glass Polythene

Microscopic structure Cyrstalline solids are based upon a simple pattern of arrangement of molecules that is repeated many times throuhout the molecule often there will be boundarys in the material where the pattern cannot be continued, these give rise to the edges of crystals and a polycrystalline material. Amorphous solids have no regular arrangement of their molecules and appear like an instantous photo of a liquid, some like glass flow very very slowly Polymeric solids are made up of long chain molecules, wrapped around each other. The polymer chains are made up repeated monomers.

Notes:

The mean molecular separation increases with temperature for all states.
The mean is taken to account for the oscillation in the molecules.
These ideas can be seen most clearly by reference to th energy/separation graph.
We assume that the graph which is for an isolated pair, also applies here.

Rob Coles 17 April 1996 10:02:43

	Crystalline	Amorphous	Polymerics
Example	Diamond	Glass	Polythene
Microscopic structure	Cyrstalline solids are based upon a simple pattern of arrangement of molecules that is repeated many times throuhout the molecule often there will be boundarys in the material where the pattern cannot be continued, these give rise to the edges of crystals and a polycrystalline material.	Amorphous solids have no regular arrangement of their molecules and appear like an instantous photo of a liquid, some like glass flow very very slowly	Polymeric solids are made up of long chain molecules, wrapped around each other. The polymer chains are made up repeated monomers.