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Gases
Structure:
The particles of gas, either atoms or molecules, have
too much energy to remain attached to one other. The move by
translation, rotation and vibration, but in this case the
translational motion is the most important. The particles
are on average
very far apart and collide
incessantly many times a second. Because of the distance
between them it is assumed that the
forces of attraction between
the particles are negligible.
Bulk properties:
Materials in the gas phase have
no fixed shape, that is,
they take on the shape of the
container. Gases have no fixed volume, the motion of
the particles is so great that the forces of attraction
between the particles are not able to hold them together. A
certain amount of gas at a pressure of one atmosphere and a
volume of ten liters could become five liters if the
pressure was increased or would become more than ten liters
if the pressure was decreased. The gas expands to fill the
container.
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Liquids
Structure:
Liquids are materials in which the smallest particles are as
close together as solids, but the particles can slip over
each other to change places. They can
vibrate, rotate and translate
but the forces that hold the particles of liquid
close to each other are greater than the forces due to
motion that would force the particles away from each other.
Bulk properties:Liquids
have no fixed shape except for
the shape of the container but do have a
fixed volume. Liquids
can not be compressed under common pressures.
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SOLIDS
Structure:
Solids may be ionic, metallic, simple covalent or giant
covalent, but all of these structures have something in
common; the smallest particles are not free to move, they
are held close together in
fixed positions by the forces around them. The only motion
allowed is vibration and this is how they absorb energy. A
particle in a solid will vibrate more and more as the
temperature rises until eventually it has enough energy to
break free from the forces holding it in position. This
happens at the melting temperature.
Bulk properties:Solids
show a definite shape and a
definite volume. Unless
forces are used that are not commonly found near the earth’s
surface, solids can not be compressed.
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