This document discusses key concepts in chemistry including thermal energy, the kinetic molecular theory of matter, and states of matter. It begins by defining thermal energy as the energy of a body due to the motion of its particles, which is directly proportional to temperature. It then explains kinetic and potential energy. The document goes on to discuss how the three states of matter arise from a competition between intermolecular forces and thermal energy. It also summarizes the kinetic molecular theory and how it applies to solids, liquids, and gases. Finally, it briefly defines and compares the processes of diffusion and effusion.

1. Presented By
NEHA AGARWAL
M.Sc In Chemistry(hons)

2. CHEMISTRY

3. BASICALLY FOR
UPPER PRIMARY CLASSES
(VI-VIII)
[BUT STUDENTS OF UPPER CLASSES
CAN ALSO FOLLOW IT ]

4. MATTER
&
ITS COMPOSITION
[ PART –II ]
Learning Outcomes :
 THERMAL ENERGY
 INTER-MOLECULAR FORCES vs THERMAL ENERGY OF THREE STATES
OF MATTER
 KINETIC MOLECUALR THEORY OF MATTER
 BROWNIAN MOTION
 DIFFUSION
 EFFUSION

5. THERMAL ENERGY
The thermal energy is the energy of a body due to motion or movement of its atoms
or molecules.
 It is directly proportional to the temperature of the substance.
 It is a measure of average kinetic energy of the particles of the matter and is responsible for
the movement of particles.
 This movement of particles is called thermal motion and keeps the molecules apart.

6.  POTENTIAL ENERGY & KINETIC ENERGY
• Potential energy is the energy in a body due to its position. An object
can store energy as the result of its position . This stored energy of position is
referred to as potential energy... Potential energy is the stored energy of position
possessed by an object.
• While kinetic energy is the energy in a body due to its motion.

9. Thermal Energy vs Inter-molecular force
of attraction
According to particle concept of matter, all matter consists of tiny
particles(atoms, molecules)which are constantly moving in all
directions. These particles exert attractive forces upon one another
called Inter-particle or inter-molecular forces. Whereas Thermal
energy which moves the molecule apart.
Therefore the three states of matter arise due to the competition
between the Inter-molecular force of attraction and Thermal
Energy.
So they are “INVERSELY PROPORTIONAL TO EACH OTHER”, means when
we go from solid to gaseous states…Inter-molecular force of
attraction decreases & thermal energy increases and vice-versa.
In GASES.. MOLECULES HAVE LOWEST INTER-MOLECULAR FORCE BUT
HIGHEST THERMAL ENERGY & IN SOLIDS…MOLECULES HAVE
HIGHEST INTERMOLECULAR FORCE BUT LOWEST THERMAL ENERGY.

10. INTER MOLECULAR FORCE & THERMAL ENERGY

11. THERMAL ENERGY depends on…
1. MASS
2. TEMPERATURE
3. NATURE & STATE OF MATTER

15. KINETIC MOLECULAR THEORY
OF
MATTER
 The word ‘KINETIC’ comes from the Greek word ‘kinos’ meaning “TO MOVE”.
 All the substance whether solids , liquids or gaseous are made of either molecules
or atoms or ions which are constantly moving. Therefore the theory describes “any
substance , whether solid, liquid or gas is composed of a large number of small
particles—individual atoms or molecules—that are in constant motion is known
as the Kinetic Molecular Theory of Matter”.

16. Why is kinetic molecular theory
important?
The kinetic theory of matter helps us to explain why matter exists in
different phases (i.e. solid, liquid and gas), and how matter can
change from one phase to the next. The kinetic theory of matter also
helps us to understand other properties of matter.
 State of Matter on the Basis of the Kinetic Theory : The three state
of matter differ from one another on account of…
1. The state of packing of their constituent particles.
2. Energies associated with these particles.
3. Intermolecular forces between them.
Let us describe the main postulates of kinetic theory of matter
individually

17. Kinetic Molecular Theory for Solids
1. Solid state of matter is composed of microscopic particles called atoms,
molecules or ions.
2. Particles are closely packed , their position are also fixed.
3. Particles are held together by strong intermolecular forces , have definite shape
and volume.
4. Particles in constant motion , have spaces lying them. They can vibrate only
about their mean position. Therefore they have small energy due to their
motion. Due to their motion particles have possess kinetic energy .
5. On heating , the kinetic energy of molecules increases and they move faster.

18. Kinetic molecular theory for Liquids
 Liquids are composed of microscopic particles called atoms
molecules or ions.
 The particles of liquids are loosely packed, their positions are not
fixed.
 Due to weak intermolecular force of attraction, particles are always
in a state of motion , move randomly.
 The average kinetic energy of particles in a given sample is
proportional to the absolute temperature.

19. KINETIC MOLECULAR THEORY OF GASES
 All gases are made of a very large numbers of tiny identical particles, atoms or
molecules.
 The particles are considered to be point masses. Because the particles separated
from one another by large distances . Intermolecular space is so large that the
actual volume of the particles is negligible as compared to the total volume of gas.
 They move completely independent of one another as there are no forces of
interactions neither attraction nor repulsion between the particles at normal
temperature & pressure.
 The particles are in a state of random motion in all directions. During their motion
they keep colliding with one another and also the walls of the container and thus
change their directions…This type of motion is known as ‘BROWNIAN MOTION’.
 Molecular collisions are elastic in nature means no loss or gain of energy occurs
when molecules collide with one other or with the walls of container.
 Gas pressure exerted by the gas is due to the collision of its particles on the wall
of the container.
 The average kinetic energy of the gas particles is directly proportional to the
temperature means an increase in temperature speed of gas particles increase.
 Lighter gas particles move faster than heavier particles.

20. Brownian motion is caused by the
random buffeting of small
particles by atoms and molecules
which are constantly moving. The
particles must be small enough to
move by BROWNIAN MOTION.

21. DIFFUSION
Diffusion is the process
whereby gaseous atoms and molecules
are transferred from regions of relatively
high concentration to regions of
relatively low concentration.
 Gaseous particles tend to
undergo diffusion because they have
kinetic energy. Diffusion is faster at
higher temperatures because
the gas molecules have greater kinetic
energy.
 You can smell perfume because it diffuses
into the air and makes its way into your
nose. A teabag placed in a cup of hot
water will diffuse into the water. Placing
food coloring in a liquid will diffuse the
color. ... These are some
common examples of diffusion of gases.

22. EFFUSION
 Effusion is also similar like
diffusion, this is the
process where gas
particles escape from an
evacuated container
through a small hole.
Example like…
Effusion, is the escape
of gaseous molecules
through a small (usually
microscopic) hole, such as
a hole in a balloon, into an
evacuated space.

23. Difference between Diffusion & Effusion

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