The basic ideas of the kinetic
- all matter consists of particles (atoms or molecules)
- as the temperature increases, the average speed of the
According to this theory, the temperature of a body is
a measure of the average kinetic energy of it particles.
This theory can also be used to explain the differences
between the different states (or phases) of matter.
The particles vibrate around fixed positions. They are
close together and so attract each other strongly. This
is why solids maintain their shape.
The particles are still relatively close together but now
have enough energy to "change places" with each
other. This is why liquids can flow.
Average distance between particles typically 10 times greater
than in solids and liquids. The particles now move freely
at random, occupying all the space available to them.
This process can be thought about as being similar to this....
100 people in you living room, all glued to the floor. They
can all move a little but can't move their feet.
You now feed them all some high energy food which gives
them enough energy to pull their feet free, so they can
now move around. Unfortunately the door is locked so they
are all still VERY close together, but at least they can
move a little. To continue the analogy from above, this
can be thought of like this...
Your room full of moving (liquid) people is now given some
even higher energy food. They now have enough energy to
break the door down (and some of the walls too). This means
that they can spread out because they can get outside -
just like a gas.
- Solids are made up of particles which are attached together
and can only vibrate back and forth.
- Liquid's particles are still held together but are able
to move around each other.
- Gas has particles which have enough energy to have broken
the bonds that held them together as a liquid.
- To go from solid to liquid to gas you need to add energy
- To go from gas to liquid to solid you must remove energy
- Solid - Liquid = Melting, Liquid - Gas = Evaporating
- Gas - Liquid = Condensing, Liquid - Solid = Freezing