This content explains the three states of matter (solid, liquid, gas) and how substances transition between them, using the particle theory model to illustrate the behavior of particles in each state.
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in today's video we're going to look at
the three states of matter
solid liquid and gas
and see how substances can change from
one state to another
to do this we're going to use a model
called particle theory which helps us
explain how the particles in each state
behave by considering each particle as a
in solids there are strong forces of
attraction between the particles
which holds them all close together in a
fixed position
to form a regular lattice structure
and because the particles are fixed the
overall substance keeps a definite shape
and volume so you can't flow like a liquid
liquid
the particles can vibrate in their
position though
so you can imagine them constantly
jostling against each other
now if we heat up a solid its particles
gain more energy and start to vibrate
even more
which weakens the forces between them
and at a certain temperature which we
call the melting point the particles
have enough energy to break free of
their bonds and the solid melts into a liquid
liquid
in liquids there are only weak forces of
attraction between the particles
so they're free to move around and are
arranged pretty randomly
however the weak forces of attraction do
mean that the particles tend to stick
together and are fairly compact
this means that liquids have a definite volume
volume
even though the overall shape can change
if we then heat up our liquid the
particles will gain more energy
and this will make the particles move
around faster
which weakens the forces holding the
particles together
and once we reach the boiling point the
particles will have enough energy to
break the bonds altogether
and so the liquid boils or evaporates
in gases the force of attraction between
the different particles is very weak
so they're basically free to move around
by themselves
this means that gases don't keep a
definite shape or volume and instead
will always fill a container as they
spread out as much as possible
we normally say that gases are
constantly moving with a random motion
and this can be a bit confusing because
gas particles actually move in straight
lines they don't randomly swerve
what we actually mean by random motion
is that particles can travel in any
direction and they'll end up being
deflected by solid walls or other gas
when we heat up a gas and the particles
all get more energy and so travel faster
the gas will either expand if the
container it's in is expandable like a balloon
balloon
or if the container is fixed then the
on the other hand if we cool the gas
down enough then the particles won't
have enough energy to overcome the
forces of attraction between them
and so bonds will start to form between
the particles
then as we call the liquid even further
the same thing happens
the particles won't have enough energy
to overcome the attraction between them
and this time even more bonds form
fixing the particles in place and
now the last thing we need to mention is
that the particle model we used for
explaining the states of mata isn't perfect
perfect
in reality particles aren't actually
solid inelastic or spheres
instead they're atoms ions or molecules
another issue is that the model doesn't
include any details of the forces
between the particles
for example it doesn't consider how
strong they are or how many of them
there are
that said models like this are still a
useful simplification that allow us to
anyway that's all for today so if you
enjoyed it then please share with your
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