Chapter 1
Kinetic Particle Theory
1.1 States of Matter
• Matter can exist as a solid, liquid or a gas
• These three forms of matter are known as
states of matter
• For instance, water(liquid) can exist as
ice(solid) or water vapour (gaseous).
Changes of State
• Melting, freezing, boiling and
condensation are example of changes of
state
1.2 Kinetic Particle Theory
• The kinetic particle theory states that all
matter is made up of particles and that
these particles are in constant, random
motion.
Uses of KPT
– Describe the states of matter
– Explains the differences in particles of solid,
liquids, gases
– Explains the changes of states.
1.2 Kinetic Particle Theory
Solid State
• Particles of solid are closely
packed in orderly manner
• Vibrate about their fixed
positions
1.2 Kinetic Particle Theory
Why does a solid have a fixed shape and a
fixed volume?
• Particles of a solid are held together by very
strong forces attraction which cannot
move freely.
• Solid cannot be compressed since its
particles are already very close to one
another
1.2 Kinetic Particle Theory
Liquid State
• Particles of a liquid are quite
closely packed in disorderly
pattern
• The particles roll and slide over
one another.
1.2 Kinetic Particle Theory
Why does a liquid not have a fixed shape?
• The force of attraction between the
particles are weaker than those in solid.
• Particles of a liquid does not have a fixed
shape
• They can move freely by sliding each other.
1.2 Kinetic Particle Theory
Why does a liquid have a fixed volume?
• Particles of a liquid are farther away from
one another than the particles in a solid.
• Particles of a liquid are packed quite
closely together.
1.2 Kinetic Particle Theory
Gaseous State
• Particles of a gas are spread
far apart from one another
• As the force of attraction
between the particles are weak.
1.2 Kinetic Particle Theory
Why does a gas not have a fixed shape and
a fixed volume?
• Particles of a gas have a lot of kinetic
energy and are not held in fixed positions.
• They can move about rapidly in any direction
• Particles can be compressed and move
closer to each other.
1.3 Changes of state and the
Kinetic Particle Theory
Melting
 When a substance changes from a solid to a
liquid, we say that melting takes place.
*What happens to particles of a solid that is heated
until it melts?
As heat energy is supplied, the particles vibrates,
until the vibrations of the particles overcome the
attractive forces between them.
1.3 Changes of state and the
Kinetic Particle Theory
Melting
Particles begin to break away from
their fixed positions. Particles slide
over one another it becomes liquid.
1.3 Changes of state and the
Kinetic Particle Theory
Melting
A–B:
B
A
Temperature of the solid increases the
unit until it reaches point B (Melting point).
Solid begins to melt.
1.3 Changes of state and the
Kinetic Particle Theory
Melting
B-C :
B
A
C
Mixtures of solid and liquid exists here.
During melting process, temperature of
substance remains constant even though
heating continues. All heat energy taken
in by paritcles is used to overcome force
of attraction between particles.
1.3 Changes of state and the
Kinetic Particle Theory
Melting
D
B
C
C-D
All solids has melted and
temperature of liquid rises as heating
continues.
A
1.3 Changes of state and the
Kinetic Particle Theory
Freezing
 When a substance changes from a liquid to a
solid, we say that freezing takes place.
*What happens to particles of a liquid that is cooled
until it freezes?
Particles lose kinetic energy and begin to move more
slowly. When the temperature is low enough, some
particles start to settle into fixed positions. Finally, all
particles settle into fixed positions. Substance now is
a solid
1.3 Changes of state and the
Kinetic Particle Theory
Freezing
P
P–Q:
Q
Temperature of liquid drops until it reach
point Q, freezing point of napthalene. At
point Q, liquid starting freezes.
1.3 Changes of state and the
Kinetic Particle Theory
Freezing
P
Q - R:
R
Q
During the freezing process, the
temperature of substance remains the
same even through cooling continues.
1.3 Changes of state and the
Kinetic Particle Theory
Freezing
R - S:
P
At point R, substances solidified.
Temperature of solid continues to drop as
it’s cool.
R
Q
S
1.3 Changes of state and the
Kinetic Particle Theory
Boiling
 As the liquid is heated, the particles gain kinetic
energy and start to move faster.
 Eventually, the particles have enough energy to
overcome the forces holding them together
 They spread far apart and move rapidly in all
directions. The substance now is a gas.
1.3 Changes of state and the
Kinetic Particle Theory
Boiling
 How does the temperature of a liquid change
when it boils?
When liquid is heated, its
temperature increases till its
boiling point is reached.
Here, it boils & changes into a
vapour. The temperature
remains constant till all liquid has
boiled off
1.3 Changes of state and the
Kinetic Particle Theory
Evaporation
 Evaporation occurs because some particles have
enough energy to escape as a gas from the
surface of the liquid.
 Liquids that evaporate quickly at room
temperature are called volatile liquids.
 Petrol and perfume are examples of volatile
liquids.
1.3 Changes of state and the
Kinetic Particle Theory
Condensation
 Heat energy is given out during Condensation
 As the temperature drops, the gas particles lose
energy and move more slower.
 Eventually, the movement of particles become
slow enough for the gas to change into a liquid.
1.3 Changes of state and the
Kinetic Particle Theory
Sublimation
 When a substance sublimes, it changes directly
from a solid to a gas.
 Dry Ice, Solid iodine, ammonia chloride
sublimes.
 A substance sublimes because the forces
between the particles in liquid state are too
weak to remain in the state.