The document describes the key points of the kinetic particle theory. It explains that kinetic particle theory views matter as being made up of tiny particles in constant random motion. It also describes the three states of matter (solid, liquid, gas) in terms of the arrangement and motion of particles. Specifically, it explains how the properties of each state, such as compressibility and ability to change shape, can be understood by considering the forces between particles and how tightly or loosely packed they are.

1. Kinetic Particle Theory
(Kinetic Model of Matter)

2. You are expected to…
•
describe the three states of matter and explain their interconversion in terms of the kinetic particle theory.
•
show understanding that Brownian motion provides
evidence for the kinetic molecular model of matter.
•
explain everyday effects of diffusion in terms of particles,
e.g. the spread of perfumes and tea/coffee grains in water.
•
describe qualitatively the molecular structure of solids,
liquids and gases, relating their properties to the forces and
distances between molecules and to the motion of the
molecules.

3. Recall: What is Matter?
•
Objects that have mass and occupy space
are called matter.

4. Question:
Is this glass bottle
empty?
No. It is filled with air!

5. Recall: How do we classify matter?
• What are the three
states of matter?
Matter
• Do you know that there
are more than three
states of matter?
- Plasma
- Bose-Einstein
condensate
Solid
Liquid
Gas

6. Recall: Properties of each state of
matter
Solids
Shape
fixed shape
Volume
fixed volume
Ability to be
compressed
Liquids
Gases
no fixed shape no fixed shape
fixed volume
no fixed
volume
incompressible incompressible compressible

7. What is matter made of?
Let’s see what the
philosophers have
to tell us…

8. Democritus
“…if one were to break up matter
into smaller and smaller piece,
there would come a point when it
could no longer be divided
further.”
He called this smallest indivisible
bit of matter ‘atom’ (from the
Greek word atomos which means
indivisible).
Greek Philosopher
(460 B.C. – 370 B.C.)

9. Aristotle
“Matter has a continuous
composition and that it can be
broken down into smaller and
smaller pieces forever.”
Aristotle was highly regarded and
most people followed his school of
thought about the nature of
matter
Philosopher
(384 B.C. – 322 B.C.)

10. Who is
right?
Democritus
or Aristotle?
Let’s
vote!
Let’s see who’s right…

11. Brownian Motion

12. Brownian Motion
Think, Pair, Share
• Describe the motion of pollen grains in water and the smoke
particles in air.
– Moving constantly in a random or irregular motion
• What caused these motions?
– Pollen grains and smoke particles were bombarded by water
molecules and air particles respectively which themselves were
moving constantly and randomly.

13. Brownian Motion
• The constant and random motion of small solid particles in
fluids (liquids and gases) is called Brownian motion.
• Brownian motion provided the evidence of molecular motion
& proved the existence of particles that cannot be observed
with a normal microscope.
• Just for info:
Brownian motion is first observed in 1827 by Robert Brown.
Through the microscope, he observed the motion of pollen
grains suspended in water. However, he was unable to
provide an explanation for Brownian motion.

14. Particles that make up of matter
• Using a scanning tunneling microscope (STM), scientists are
now able to observes the particles that make up matter.
Gold atoms

15. Particles that make up of matter
Iron on Copper

16. So, who’s right?
In conclusion…
Matter is made up of discrete
(separate not continuous) particles
which are in constant and random
motion.
In other words…
Democritus
(460 B.C. – 370 B.C.)
Democritus’ proposal that matter is
made up of tiny particles is right!

17. Kinetic Model of Matter (Kinetic
Particle Theory)
• Based on observations, a model (Kinetic Model of
Matter) which explains the nature of matter was
proposed.
• The Kinetic Model of Matter (Kinetic Particle
Theory) states that matter is made of tiny discrete
particles (atoms or molecules), which are in
constant and random motion.
• Energy due to movement = Kinetic energy

18. Remembered this?
Solids
Shape
fixed shape
Volume
fixed volume
Ability to be
compressed
Liquids
Gases
no fixed shape no fixed shape
fixed volume
no fixed
volume
incompressible incompressible compressible
Kinetic Model of Matter can be used to explain the
properties for each state of matter

19. Kinetic Model of Matter (Kinetic
Particle Theory)

20. Video: Things to look out for
•Arrangement of
particles
•Motion of particles
•Attractive forces
between particles
•Speed of particles
(if any)

21. Particles in a Solid
Arrangement Closely packed together in a
fixed, regular pattern, occupying
minimum space.
This results in solids having high
densities

22. Particles in a Solid
Movement
Cannot move freely but vibrate
about fixed positions.
Held in position by very strong
attractive forces
This explains why solids have
fixed volumes and shapes

23. Particles in a Liquid
Arrangement
Randomly arranged with
the particles slightly
further apart as
compared to that of
solids.
This results in liquids
having relatively high
densities

24. Particles in a Liquid
Movement
Particles slide past one
another
Free to move about but
confined within the
vessel containing it.
Have attractive forces
between particles.
This explains why liquids
have fixed volume but
will take the shape of
vessels containing them.

25. Particles in a Gas
Arrangement
Very far apart. Particles
are randomly arranged
and will occupy any
available space.
This results in gases
having relatively very
low densities

26. Particles in a Gas
Movement
Particles have very little
attraction between them
and move about
randomly at a very high
speed..
This explains why gases
have no fixed volume
and shape, and why they
are highly compressible.

27. The states of matter
• The relative strength of the intermolecular
forces between the particles differ between
the different states of matter

28. The states of matter
• The relative distances between the particles
also differ between the different states of
matter

29. A Summary…
• Matter is anything that has mass and occupies
space
• All matter can exist in 3 physical states,
– Solid
– Liquid
– Gas
depending on the temperature and pressure
of their surroundings

30. Solid
Liquid
Gas
Fixed
Fixed
Takes the
volume of its
container
Shape
Fixed
Takes the shape
of the part of
the container it
fills
Takes the shape
of the container
Density
High
Medium
Low
Expansion
on heating
Little
Moderate
Large
Ease of
compression
Difficult
Difficult
Easy
Volume

31. A Summary…
So why do solids, liquids and gases
have such different properties?
Kinetic Particle Theory

32. Kinetic Particle Theory
• Matter is made of tiny discrete particles
(atoms or molecules), which are in constant
and random motion.
• Energy due to movement = Kinetic energy

33. Evidence of Kinetic Particle Theory?
• Diffusion – particles moving randomly from a
region of high concentration to lower
concentration
• in gases
• in liquids
• in solids???

34. Thinking Question:
• Now that you know the arrangement
/movement of particles in solids, liquids and
gases, can you compare the rates of particle
movement (diffusion) in liquids and gases, and
explain why it is so?

35. Thinking Question:
• If a solid is usually more dense than a liquid,
why does ice float on water?

36. Change in State of Matter

37. Matter
Solid
Melting
Liquid
Freezing
Boiling
Gas
Condensation
Deposition
Sublimation

38. Change in State of Matter
gas
Temperature / °C
liquid-gas
liqu
id
boiling point
boiling
solid-liquid
sol
id
melting point
I
melting
II
III
IV
V
Time / s

39. Change in State of Matter
Temperature / °C
gas
liquid-gas
condensation
point
condensation
liquid
solid-liquid
freezing point
freezing
I
II
III
IV
solid
V
Time / s

40. Role play 

41. Melting
• When a solid is heated, the particles absorb thermal
energy. The particles gain kinetic energy and start to
vibrate faster and move further apart . At a certain
temperature known as the melting point, the particles
have enough kinetic energy to overcome the strong
forces of attraction holding the particles together in the
solid. The particles start to break away from one
another and the solid becomes a liquid.
• At the liquid state, the particles start to roll and slide
over one another

42. Melting
• In other words, during phase II (melting), thermal energy
supplied is used to do work to overcome the strong forces of
attraction holding the particles together in the solid.
Temperature / °C
boiling point
melting point
I
II
III
IV
V
Time / s

43. Freezing
• When a solid is cooled, the particles release
thermal energy. The particles lose kinetic
energy and vibrate slower. At a certain
temperature known as the freezing point, the
particles no longer have enough kinetic
energy to overcome the strong forces of
attraction holding them together. The
particles start to come together in a regular
arrangement and the liquid becomes a solid.

44. Boiling
• Particles in a liquid are held by strong attractive
forces.
• When a liquid is heated, the particles absorb thermal
energy. The particles gain kinetic energy and slide
over each other more rapidly.
• Eventually, the particles gain sufficient energy to
overcome the attractive forces between the
particles in a liquid and move far apart rapidly in all
directions.

45. Summary of today’s lesson
• All matter is made up of a tiny discrete
particles in constant random motion
• The particles in a solid, liquid and gas are
arranged differently – so they have different
properties
• During change of state, the particles gain or
lose energy, resulting in a change in the
arrangement of the particles

46. Thinking question
• A liquid expands and changes into gas during
boiling. Does it mean that the particles in a
liquid become bigger and change their shape?
• The liquid expands because the particles move
farther apart, so the space between them is
bigger. The particle remain the same in size
and shape.