KINETIC MODEL OF MATTER!
Introduction:
Hey
again everyone! Hope you are all fine. Today the topic we are going to study is
the Kinetic Model of Matter. We have all studied it in the previous classes,
easy wasn’t it? Let’s get started!
States of Matter:
Okay
so matter can exist in three states as we all know namely the solids, liquids
and gases. These are called the states of matter. As shown below, water
(liquid) can exist in ice (solid) and water vapour (gas).
So
what is the kinetic model of matter? It states that:
1.
All matter is made of tiny particles which exist as atoms, molecules and ions.
2.
The particles are always in continuous, random motion and hence, possess
kinetic energy. The kinetic energy of a particle increases with temperature and
pressure and at fixed temperature, lighter particles move faster.
The
three states differ in arrangement and movement.
Here’s
a simple diagrammatic representation of the states:
Now
lets get into detail about these.
Solids
●
Solid
particles of are tightly packed,
●
Solid
particles vibrate about a fixed position,
●
Solids
have a definite shape and a definite
volume,
●
Solids
cannot be easily compressed because of very less free space between particles
and
●
Solids
do not flow because the particles cannot move or slide over one another.
Liquids
●
Liquids
have a definite volume, but do not have a definite shape since because of less
tightly packed liquid particles as compared with solids,
●
Liquid
particles are far enough apart to slide over one another and therefore, liquids
flow easily and
●
Liquids
cannot compress easily since there is less free space between particles as
compared with gases.
Gases
●
Particles
of gases are much far apart and move freely and therefore, gases do not have a
definite shape or a definite volume,
●
Because
of more free space between particles, gases can be easily compressed and
●
Because
of the random and faster movement of the particles as compared with solids or
liquids, gases can flow very easily.
Now
if you relate the properties with one another, they’ll be easy to memorize and
will seem pretty much logical. Like for instance, why can’t solids be
compressed while gases can be? That difficult? Oh no, it’s not! Gases move at
very high speed, we know, which causes them to have a lot of space between their particles. So,
they can be compressed and brought closer but just think, can you bring the
already so close particles of solid more closer? Of course not. So just try to make sense out
of it, it’s not that difficult.
Pressure in Gases:
First
of all, what is pressure? We have already studies in the tutorial on Pressure
that is the force acting per unit area.
p-T
relationship:
How
are pressure and temperature related. Do you know that if you heat a container
containing gas, the gas particles will gain kinetic energy and move faster?
When they’ll move faster, they’ll hit the walls of container more often and
more force will be exerted on the walls per unit area. This increases the
pressure. Hence:
p α T (pressure is directly
proportional to temperature)
V-T relationship:
When a gas is
heated, it’s temperature rises, causing the molecules to move at higher speeds,
we just discussed. The pressure increases, that is, the particles collide with
the walls of container more frequently. When this happens, the gas will expand
in order to keep the pressure constant. So it will occupy more volume if it
can. Logical, right? Therefore, we can conclude:
V α T (volume is directly
proportional to temperature)
p-V relationship:
Okay so now, what
will happen to pressure if volume of gas is increased or decreased? Take a look
at the two syringes below:
The volume in 2 is
decreased by pushing the same syringe further which has caused the volume to
halve the original one in syringe 1. When we halve the volume, the number of
molecules of air per unit volume will be doubles, this will double the
frequency of collisions with the wall of the syringe and consequently, will
double the pressure. Similarly, if you double the volume, the frequency of
collisions per unit volume will decrease and the pressure will decrease to
half.
So to conclude:
p α V (pressure is directly
proportional to volume)
