LEARNING OUTCOMES
 State evidence in support of the
particulate nature of matter
 Explain the differences between the three
states of matter in terms of the arrangement
of particles
STATES OF MATTER
Chapter 1

 Matter can exist in 3 states: solid, liquid and gas.
 For example, water can exist as:
 ice (solid state),
 water (liquid state) and
 steam or water vapour (gaseous state).
STATES OF MATTER
Chapter 1
States of Matter

States of Matter
 The state in which a substance exists depends mainly
on its temperature and pressure.
 For example, iron is a solid at room temperature and
pressure; but at around 1500 oC, it becomes a liquid.
 Similarly, oxygen is a gas at room temperature and
pressure, but at –183 oC, it is a liquid.
STATES OF MATTER
Chapter 1

Chapter 1
STATES OF MATTER
Diffusion
 Diffusion is the spontaneous movement of particles of a
substance from a region of higher concentration to a region of
lower concentration.
 Diffusion occurs in all states of matter.
 For solids, diffusion can be shown by placing a block of gold
and a block of lead together. Some gold atoms will be found in
the lead block and some lead atoms will be found in the gold
block after a few years.

Chapter 1
STATES OF MATTER
For liquids, diffusion can be shown by placing a drop of
ink or a crystal of purple potassium manganate(Vll) into a
beaker of water.
Diffusion
After some time, a uniform purple colour is seen
throughout the beaker.

For gases, diffusion can be shown by setting up the apparatus shown below.
1.Soak a piece of swab with concentrated hydrochloric acid and insert it into
one end of the glass tube.
2. Soak another piece of cotton swab with concentrated ammonia solution
and insert it into the other end of the glass tube.
3. Seal both ends of the glass tube with rubber bungs and leave the tube
horizontal.
4. After a few minutes, a white disc of ammonium chloride is formed.
Diffusion
STATES OF MATTER
Chapter 1

Rate of diffusion
 The speed of diffusion is fastest in
gases followed by liquids and very
slowly in solids.
 The rate of diffusion increases with
temperature.
 At higher temperatures, the particles
have higher kinetic energy and hence
move faster and diffuse at a faster
rate.
At O oC
At 2O oC
The Three States of Matter
Chapter 3

Rate of diffusion
 The rate of diffusion also depends
on the relative molecular mass of
the particles.
 Heavier particles will
diffuse at a slower rate
than lighter particles.
 The rate of diffusion of a gas is
inversely proportional to the
square root of its relative
molecular mass.
The Three States of Matter
Chapter 3

Chapter 1
STATES OF MATTER
Osmosis
Osmosis is the movement of water molecules from a
region of higher water concentration to a region of lower
water concentration through a partially permeable
membrane.
It is a special type of diffusion carried out by plants to
obtain water and mineral salts from the soil.

Differences between solids,
liquids and gases
A solid has a fixed shape and a fixed
volume. A solid cannot be compressed.
A liquid has a fixed volume but no fixed
shape. A liquid cannot be compressed.
A gas has neither fixed shape nor
volume. A gas can be easily compressed.
STATES OF MATTER
Chapter 1

Differences in properties
Solid Liquid Gas
Particles are close together,
but not tightly packed.
Particles are very far apart.
Particles are packed
closely together in an
orderly pattern.
Solid particles can only
vibrate in fixed positions
but cannot move away
from each other.
Liquid particles can vibrate
and move freely throughout
the liquid.
Gas particles can vibrate
and move very freely and
randomly in all directions.
STATES OF MATTER
Chapter 1

The Particle Theory
 According to this theory, the particles in matter are in a state of constant motion due
to their kinetic energy.
 Gas particles of a substance have more kinetic energy than liquid particles, while
liquid particles have more kinetic energy than solid particles.
 Hence, gas particles can move much more freely and quickly than liquid particles,
which in turn, can move more freely than solid particles.
 Matter can be converted from one state to another by changing the amount of
energy of the particles. If a matter gains heat energy, the particles will move faster
and further apart, thus changing from a more orderly state to a more disorderly
state.
 Conversely, if heat energy is removed from a matter, the particles will slow down
and move closer together, thus resulting in a more orderly state.
STATES OF MATTER
Chapter 1

Melting
 Melting is the change from a solid to a liquid.
 The temperature at which a solid melts is called its
melting point.
 A pure substance has a fixed melting point.
E.g. The melting point of ice is 0 oC.
Solid Liquid
melting
STATES OF MATTER
Chapter 1

Melting point graph
 During melting, heat energy is
absorbed by the solid.
 The temperature remains constant
during melting because the heat
absorbed is used to overcome the
forces of attraction between the solid
particles instead of using it to raise its
temperature.
 A melting point graph can be plotted
for a solid which undergoes heating,
and its melting point can be
determined from the graph.
Temperature/oC
Melting point

solid state
solid + liquid
Liquid state
Melting point graph
STATES OF MATTER
Chapter 1

Freezing
 Freezing is the change from a liquid to a solid. It is the reverse of
melting.
 The temperature at which a liquid freezes is called its freezing point.
 For most pure substances, the freezing point is the same as the
melting point.
E.g. The melting point of ice and the freezing point of water are both
0 oC.
SolidLiquid
freezing
STATES OF MATTER
Chapter 1

Freezing point graph
 During freezing, heat energy is
released (given out) by the liquid
particles as they slow down and move
closer together to take up the orderly
positions of a solid.
 The temperature remains constant
during freezing because the heat
given out compensates for the loss of
heat to the surroundings.
 A freezing point graph (or cooling
curve) can be plotted, and the freezing
point of the liquid can be determined
from the graph.
Temperature/oC
Freezing
point 
solid statesolid + liquid
Liquid state
Freezing point graph
STATES OF MATTER
Chapter 1

Boiling
 Boiling is the change from a liquid to a gas or vapour.
 The temperature at which a liquid boils is called its boiling point.
 A pure substance has a fixed boiling point.
E.g. The boiling point of water is 100 oC under normal
atmospheric pressure.
Liquid
boiling
Gas
STATES OF MATTER
Chapter 1

Boiling point graph
 During boiling, heat energy is absorbed
by the liquid particles to change into a
gas.
 The heat energy absorbed is used to
overcome the forces of attraction
between the liquid particles and to
increase their kinetic energy until they
have sufficient energy to escape from the
liquid.
 The temperature of a liquid remains
constant during boiling as the heat
energy absorbed is used to increase the
kinetic energy of the particles and not to
raise its temperature.
Boiling
point 
Liquid state
Liquid + gas
Gaseous
state
Boiling point graph
STATES OF MATTER
Chapter 1

Chapter 1
STATES OF MATTER
Evaporation
 Evaporation is the change from liquid into gas without boiling.
E.g. A drop of ethanol or perfume evaporates at room temperature.
 Evaporation occurs below its boiling point.
 Evaporation only takes place at the surface of a liquid.
 Evaporation takes place slowly.
 Evaporation produces a cooling effect because heat energy is absorbed
from the surroundings.

Condensation
 Condensation is the change from a gas to a liquid.
It is the reverse of boiling.
 Heat energy is released (given out) during
condensation as the gas particles slow down and
move closer together to become a liquid.
 The temperature of a substance remains constant
during condensation since the heat given out
compensates for the loss of heat to the
surroundings.
STATES OF MATTER
Chapter 1

Sublimation
 Sublimation is the change from a solid directly into a gas
without melting.
 For example, iodine crystals sublime into purple iodine
vapour when heated.
Solid Gas
Iodine vapour
Solid iodine
Sublimation
 Other examples of solids which sublime are dry ice,
ammonium chloride and naphthalene.
STATES OF MATTER
Chapter 1

Summary
Liquid
Gas
Solid
Melting
(energy absorbed)
Freezing
(energy released)
STATES OF MATTER
Chapter 1

Quick check 1
1. State whether heat energy is absorbed or released in each of the following
processes:
(a) melting, (b) boiling, (c) freezing, (d) condensation
2. State whether the speed of the particles increases or decreases during:
(a) melting, (b) condensation, (c) boiling, (d) freezing
3. The information below gives the melting points and boiling points of four
substances:
Substance Melting point (oC) Boiling point (oC)
W −123 −150
X −59 247
Y 98 597
Z 20 125
(a) For each substance, state whether it is a solid, a liquid or a gas at room
temperature and pressure.
(b) In which substance are the particles furthest apart at −60 oC?
Solution
Chapter 1
STATES OF MATTER

Solution to Quick check 1
1. (a) melting – heat absorbed, (b) boiling – heat absorbed,
(c) freezing – heat released, (d) condensation – heat released
2. (a) melting – increases, (b) condensation – decreases,
(c) boiling – increases, (d) freezing – decreases
3. Substance Melting point (oC) Boiling point (oC)
W −123 −150
X −59 247
Y 98 597
Z 20 125
(a) W: gas, X: liquid, Y: solid, Z: liquid
(b) W
Return
STATES OF MATTER
Chapter 1

References
 Chemistry for CSEC Examinations by
Mike Taylor and Tania Chung
 Longman Chemistry for CSEC by
Jim Clark and Ray Oliver
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