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The units in this module are:
C2a – Paints and Pigments
C2b – Construction Materials
C2c – Does the Earth move?
C2d – Metals and Alloys
C2e – Cars for Scrap
C2f – Clean Air
C2g – Faster or Slower 1
C2h – Faster or Slower 2
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What’s in a paint?
How paints dry
What is a colloid?
Thermochromic paints
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Phosphorescent paints
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What’s in a paint?
Paints have different ingredients in them to do different jobs
Reason
Pigment
To provide colour
Binding agent
Keeps the paint attached
to the surface
solvent
Dissolves the pigment
and binding agent
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How paints dry
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Water based paints such as emulsion paints dry because the
solvent evaporates and forms a film
Oil based paints dry because the solvent evaporates and the
binding agent reacts with oxygen and harden to form a film of
paint
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What is a Colloid?
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Paint is a mixture called a colloid
A colloid is where solid particles
are mixed with liquid particles
but do not dissolve.
The solid particles are dispersed
in the liquid.
They are so small that they do
not settle on the bottom and
stay mixed.
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Thermochromic paints
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There are some special types of paints available.
Some paints contain pigments that change colour as
temperature changes
These are called thermochromic paints
Uses of these paints include: thermometers
cups
kettles
baby spoons
eggs
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Phosphorescent paints
Some paints can glow in the dark.
They contain phosphorescent pigments.
These pigments absorb and store light energy.
Uses : dash boards
warning signs
Before phosphorescent pigment were used, radioactive
materials were used on watch faces to make them glow
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For a paint you need a pigment
Blend the powder with an oil
Thin it with a little solvent
Stir it well but do not boil
Paint it on, this is your colloid
Let the solvent blow away
It’s the same with an emulsion
Of two liquids, one will stay
Left behind the binding medium
Sticks the colour to the wall
Forms a smooth protective layer
Doesn’t look too bad at all
Dyes and paints can make a statement
Dress up as a ghost or sprite
Use some paint that’s phosphorescent
Lit by day, it glows by night
Choose a colour that’s synthetic
If you want to paint the town
Or wear the latest thermochromic
Heat – or cold – will change it round
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Which materials are used?
Products from rocks
Using limestone
Making concrete
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Problems with rocks
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Which materials are used?
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Lots of materials can be used in buildings
Some examples are : glass
bricks
steel
aluminium
wood
iron
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Products from rocks
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Limestone, granite and marble are three rocks which can be
used as construction materials.
Limestone
Sedimentary rock
Made by sea creatures sinking to the bottom
of the sea and buried
Granite
Igneous rock
Formed when molten rock cools down
Marble
Metamorphic rock
Made by action of heat and pressure on
limestone
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Heating limestone
Limestone is calcium carbonate, CaCO3
Heating limestone is a thermal decomposition reaction.
Two new substance are made in this reaction
Calcium carbonate  Calcium oxide + Carbon dioxide
CaCO3

CaO
+
CO2
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Making concrete
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A lot of limestone is made into cement. Limestone and clay are
heated together.
Concrete is a useful construction material. It is made from
cement, sand, gravel and water.
Concrete is not very strong unless it is
reinforced.
Putting steel rods in concrete reinforces
it.
This makes the beams stronger and
prevents its from cracking.
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Problems with rocks
Obtaining rocks from a quarry can cause environmental
problems
They take up valuable land
space
They destroy landscapes
Destroy the environment of
plants and animals
Increase dust and noise levels
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Structure of the Earth
Plate tectonics
Evidence for plate tectonics
Subduction
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Volcanoes
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Structure of the Earth
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Crust is solid rock
Mantle is molten rock
Outer core is liquid iron and
nickel. It is very dense.
Inner core is solid iron and
nickel. It is very dense.
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Plate tectonics
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The crust and the upper mantle is called the lithosphere. The
lithosphere is made up of large sections called tectonic plates.
These plates float on top of the mantle. They move a few cm
each year.
The liquid in the mantle can move because of convection
currents and carry the plates with it.
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Evidence for plate tectonics
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Africa and South America look like
they fit together suggesting they
were once joined.
Fossils and rocks have been found
on both continents.
Earthquakes and volcanoes occur
where plates meet.
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Subduction
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When an oceanic plate and a continental plate collide, the
oceanic plate is forced underneath the continental plate.
The oceanic plate melts in the magma.
This is called subduction.
The continental plate forms fold mountains.
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Volcanoes
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Volcanoes are formed where there are
weaknesses in the Earth’s crust. Molten
rock can make its way to the surface.
Geologists study volcanoes.
People choose to live near volcanoes
because the land is fertile and lots of
crops can be grown.
There are two types of volcanic rock
Extrusive igneous rocks form outside the Earth
and have small crystals
Intrusive igneous rocks form in side the Earth’s
crust and have large crystals
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Extracting copper
Purifying copper
Alloys
Smart alloys
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Extracting Copper
Copper is a useful metal used in wires and pipes
Copper is extracted from its ore using displacement with
carbon.
This is because carbon is more reactive than carbon
Copper oxide + Carbon  Copper + Carbon dioxide
2 CuO
+
C

2 Cu
+
CO2
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Purifying copper
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Copper can be purified using electrolysis. It must be 99.9%
pure to be used in wires.
Rods called electrodes are placed in
an electrolyte (copper sulphate)
Copper metal forms on the cathode
Cu2+ + 2e-  Cu
Copper from the anode becomes
ions in solution
Cu – 2e-  Cu2+
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Alloys
An alloy is a mixture of elements where at least one is a metal.
Metals are more useful as alloys.
Alloy
Main Metal
Use
Amalgam
Mercury
Tooth fillings
Brass
Copper & Zinc
Hinges, screws, instruments
Bronze
Copper & Tin
Statues
Solder
Tin & Lead
Joining metals, circuits
Steel
Iron
Car bodies, ships
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Smart Alloys
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Smart alloys are also known as shape memory alloys.
Shape memory alloys can return to their original shape when put
in hot water or an electric current is passed through it.
Uses of shape memory alloys are:
 originally for military uses
 medical uses
 spectacle frames
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Corrosion of iron
Corrosion of aluminium
Properties of iron and aluminium
Car bodies
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Corrosion of Iron
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Iron is the only metal that rusts.
Iron needs oxygen and water to
rust. Rusting is speeded up by salt
water or acid rain.
Iron + Oxygen + Water  Hydrated Iron Oxide
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Corrosion of Aluminium
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Aluminium does not corrode even in
damp conditions.
This is because it forms a layer of
aluminium oxide.
This prevents the surface from
corroding.
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Properties of Iron and Aluminium
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Property
Iron
Aluminium
Density
Denser than steel
Lees dense than
iron
Magnetism
Magnetic
Not magnetic
Corrosion
Rusts easily
Does not corrode
easily
Malleability
Malleable
Malleable
Conductivity
Good conductor
Good conductor
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Car Bodies
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Steel is used to make car bodies. It is
harder and stronger than iron. It is also less
likely to corrode than iron.
Stainless steel was used to make a
car body. It is more expensive than
steel but did not rust.
Aluminium can be used instead of steel.
Aluminium cars are lighter and give
better fuel economy. An aluminium
frame also corrodes less,
However, repair costs are approximately
25% more than steel.
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Composition of air
Evolution of the atmosphere
Air pollutants
Controlling air pollution
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Composition of Air
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Air is a mixture of gases.
It is:- 78% nitrogen
21% oxygen
1% other gases
The other gases include carbon dioxide, water vapour and
argon.
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Evolution of the Atmosphere
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The atmosphere has remained constant for millions of years.
Atmosphere formed from volcanic
eruptions was made of carbon dioxide,
water vapour, methane and ammonia.
Water vapour cooled and
formed oceans.
Plants form and convert
carbon dioxide into
oxygen
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Air Pollutants
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Pollutant
How is it formed?
Problem
Carbon
monoxide
Formed from
incomplete combustion
in car engines
Is a poison and
prevents oxygen
transport around body
Nitrogen oxides
In car engines from
the reaction of
nitrogen with oxygen
Creates smog, acid
rain and breathing
problems
Sulphur dioxide
Combustion of fossil
fuels containing
sulphur e.g. coal
Acid rain
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Controlling Air Pollution
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The balance between carbon dioxide and oxygen can be changed
by humans
Increasing energy use means more carbon dioxide
Population increase means more carbon dioxide
Deforestation means more carbon dioxide
Catalytic converters can be fitted to car exhaust systems to
change poisonous carbon monoxide and nitrogen oxides into
carbon dioxide and nitrogen.
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What are rates?
Measuring rates
Rates and graphs
Temperature and rates
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Concentration and rates
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What are Rates?
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Chemical reactions are different. The rate of reaction is the
time it takes for a reaction to complete.
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Measuring Rates
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We can measure the rate of
reaction by timing how long it
takes for a product to form (e.g.
a gas) or a reactant to be used
up (e.g. a solid)
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Rates and Graphs
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The graph starts steeply. This is
when the reaction is fastest. When
the line is flat, the reaction has
stopped.
We can compare two
reactions. The one with the
steepest line is the quickest
reaction.
We can calculate initial rate of
reaction by working out the
gradient = volume of gas(cm3)
time(s)
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Temperature and Rates
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Particles of reactants must collide for a reaction to occur.
As the temperature is increased the particles move faster
because they have more energy.
This means the particles collide more often and with enough
energy. More collisions mean a faster reaction.
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Concentration and Rates
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As the concentration is increased there are more particles in a
given volume.
The particles are closer together
There will be more collisions and the reaction will be faster.
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Surface area and rates
Catalysts and rates
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Surface Area and Rates
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If we break up a solid reactant into smaller pieces, we increase
the surface area.
Because more surface area is exposed, the particles collide
more frequently.
More collisions mean a faster reaction.
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Catalysts and Rates
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Catalysts are chemicals which speed up a chemical reaction.
They are not used up during a reaction and do not change how
much product is made, they just make it happen faster.
Catalyst are specific – each catalyst only works for certain
reactions
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