Recall the four principles or characteristics of the particle
model:
How do these microscopic ideas explain the macroscopic properties
of solids, liquids, and gases we gave in the previous video
session? Although all characteristics of the particle model
help to explain these properties, we also pick out the most
important characteristic related to each property.
|
Phase |
Property |
Most important characteristic |
Microscopic reason |
Solid
|
Holds shape |
There are forces between the particles. |
The forces that attract individual
particles to one another are strong enough to overcome
the tendency of their motion to pull them apart. This
results in a rigid structure. |
|
Not compressible |
There is empty space between the particles. |
Each particle can be thought of as
a rigid sphere. In a solid, the particles are touching
each other and therefore cannot be pushed together
more. |
Liquid
|
Takes shape of container |
All particles are in constant motion,
and there are forces between the particles. |
The energy of the motion of particles
is strong enough to allow the particles to move past
each other, despite the forces between particles. |
|
Not compressible |
There is empty space between the particles. |
For a similar reason to solids, the
particles can be thought of as touching each other,
so no force can compress them further. |
Gas
|
Fills container |
All particles are in constant motion. |
The energy of the motion of particles
is so great as to overcome the attraction between particles
when they collide. Individual particles then continue
on until they hit the walls of the container. |
|
Compressible |
There is empty space between the particles. |
The resulting space between the particles
is much larger than the particles themselves (i.e.
they are not touching) so it is possible to squeeze
a container to make those spaces smaller, at the expense
of increasing the pressure of the gas inside the container. |
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scaling analogies
