Chapter
1
The Particulate
Nature of Matter
1
You will learn about:
contents
•Properties of matter in the solid, liquid
and gaseous states
•The Kinetic Particle Theory
•The inter-conversion of the states of
matter
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states of matter
• All substances are made of matter.
•The three states of matter are solid, liquid and gas
gas
solid
liquid
water exist as three states of
matter
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Properties of matter in
solid, liquid and gaseous states
Main Features of Solids, Liquids and Gases
Solids
Liquids
Gases
Shape
Fixed
No fixed shape; take
the shape of
container
No fixed shape;
expand to take the
shape of container
Hardness
Hard and is usually
made of crystals
Not hard and can flow
easily
Not hard. Can flow
along a pipeline and
diffuse easily
Density
High density
medium density
Low density
Compression
No
No
Easily compressed
Fixed
No fixed volume;
expand to fill the
container
Volume
Fixed
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The Kinetic Particle Theory
•Scientists have gathered evidence from diffusion experiments,
changes in volume and changes in states and hypothesized that
matter is made up of small particles.
•The ancient Greeks were the first to suggest that everything is
made up from particles. Thus, scientists came up with the Kinetic
Particle Theory.
The Kinetic Particle Theory states
that all matter is made up of tiny
particles, and these particles of
matter are always in constant
random motion.
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particles of matter
Property
Solid
Liquid
Gas
Arrangement
and Packing
between
particles
Particles are in
orderly
arrangement and
are packed very
closely together.
Particles are not in
orderly
arrangement and is
closely packed
together.
Particles are not in
orderly arrangement
and are very far
apart from one
another.
Motion of
particles
Particles vibrate
about a fixed
position
Particles are free
to move around the
liquid and slide
over each other.
Particles are very
far apart from each
other.
Forces of
attraction
between
particles
Very strong forces
of attraction
between particles
Strong forces of
attraction between
particles
Very weak forces of
attraction between
particles
Diagrammatic
representation
of particles in
each state
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particles of matter
QuickTime™ and a
Cinepak decompressor
are needed to see this picture.
7
Inter-conversion of states of matter
melting
•When a solid is heated, particles gain kinetic energy and
vibrate faster.
•At a certain temperature, particles would have gained enough
energy to overcome the attractive forces holding the
particles of solid together in fixed positions.
•Melting occurs. Particles now are able to move around the
liquid and slide over one another.
Why is a water bath used?
temperature
Prevent direct heating
of combustible substances
stearic acid
experiment to find the
melting point of stearic acid
water at 100ºC
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HEAT
Inter-conversion of states of matter
QuickTime™ and a
Cinepak decompressor
are needed to see this picture.
9
changes of state
melting
Graph of temperature vs time plotted to depict melting process
temperature (ºC)
melting
starts
melting
point (69°C)
melting
completes
SOLID + LIQUID
SOLID
temperature remains
constant. Why?
LIQUID
Heat energy absorbed by the
particles is used to overcome
the forces of attraction holding
the particles together in their
fixed positions.
time from start (min)
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changes of state
freezing
• When a liquid is cooled, particles lose kinetic energy and move
slower and come closer together.
•At a certain temperature, particles no longer have enough energy
to move around the liquid.
•Freezing occurs. Liquid changes into a solid and particles can only
vibrate in their fixed and orderly positions. Heat energy is given
out during freezing.
•Freezing and melting points are the same for a pure substance.
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changes of state
freezing
Graph plotted to depict freezing
Heat loss due to cooling is
exactly balanced by the heat
energy liberated as the particles
attract one another to form a
solid.
temperature (ºC)
LIQUID
freezing point
(=melting point)
for pure
substances
temperature
remains constant.
Why?
SOLID
LIQUID + SOLID
freezing
starts
freezing
completes
time from start (min)
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changes of state
boiling
• When a liquid is heated, the particles gain kinetic energy and move faster.
•At a certain temperature, particles throughout the liquid gain enough
energy to overcome the forces of attraction holding them together in the
liquid.
•Boiling occurs. Liquid changes into a gas. Particles are now able to move
freely and randomly around at great speeds.
thermometer
water
out condenser
liquid
trichloroethane
experiment to find the boiling
point of 1,1,1-trichloroethane
HEAT
boiling
stones
water in
liquid
trichloroethane
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changes of state
boiling
Graph plotted to depict boiling
temperature (ºC)
The temperature remains
constant during boiling
because the heat energy is
absorbed by the particles of
liquid to overcome the forces
of attraction holding them
together.
boiling starts at point A
74ºC
A
B
liquid is boiling between
points A and B
0
Boiling occurs when the
vapour pressure of the
substance equals to the
ambient pressure.
time from start (min)
A pure substance has a fixed boiling point at a fixed pressure. Boiling
point increases when pressure increases (i.e. pressure cooker) and boiling
point decreases when pressure decreases. (on mountain top)
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changes of state
evaporation
• occurs when liquids turn into gases without boiling.
•Evaporation occurs because some particles near the surface of the
liquid have enough energy to escape as a gas.
•Liquids which vaporize quickly at low temperatures are called
volatile liquids.
•Differences between Boiling and Evaporation:
Boiling
Evaporation
occurs only at boiling point
occurs at temperatures below
boiling point
takes place throughout the
liquid
takes place at the surface of
the liquid
very fast process
very slow process
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changes of state
condensation
• When a gas is cooled, particles lose kinetic energy and move
more slowly. The particles come closer to one another.
•At a certain temperature, the particles no longer have enough
energy to move about randomly at great speed.
•Condensation takes place. The gas is changed into a liquid. Heat
energy is given out during condensation.
sublimation
• Change of state from solid to gas without melting.
•Sublimation occurs because some particles have enough
energy to break off from the solid and escape as a gas.
•Examples include iodine, ammonium chloride and solid
carbon dioxide (dry ice)
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changes of state
sublimation
QuickTime™ and a
Cinepak decompressor
are needed to see this picture.
17
energy
fixed shape
has
particles can
only vibrate
has least
solid
melting
particles
freezing
because
shape of
container
has
because
are close together in
disorderly arrangement in
particles can
mix together by
liquid
boiling
particles can move
so liquids flow
condensation particles can
mix together by
diffusion
gas
sublimation
can be
energy
compress
no shape
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