C2
Paints and Pigments
Construction Material
State that a pigment is a coloured substance that is
used in paint
Ingredients of paint
 Solvent
 Binding medium
 Pigment
Functions
Functions of a solvent :
Functions of a binding medium :
Functions of a pigment :
Aluminium
Iron
Brick
Cement
Concrete
Glass
Granite
Limestone
Marble
Some construction materials are manufactured from rocks in
the earth’s crust
– Aluminium and iron from ores
– Brick from clay
– Glass from sand
–
Environmental problems caused by removing rocks from
the ground
Landscapes destroyed and has to be reconstructed
when the mining or quarrying has finished
Quarries or mines take up land-space
Increased noise, traffic and dust
Paint
Paint is a mixture called a colloid
 A colloid is where the particles are mixed
and dispersed with particles of a liquid but
are not dissolved.
 The components of a colloid will not
separate because particles are scattered or
dispersed throughout the mixture and are
small enough not to settle at the bottom.
 Used to decorate or protect surfaces
 Many paints are applied as a thin surface
which dries when the solvent evaporates
 Emulsion paints are water based
Oil Paint
Drying of oil paints involves oxidation of
the oil by oxygen
Oil paints
– Have the pigment dispersed in an
oil
– Have a solvent that dissolves oil
Dyes
Used to colour fabrics
Some dyes are natural and other are
synthetic
Use of synthetic dyes has increased the
number of colours available to colour
fabrics
Thermochromic Paint
Thermochromic pigments change colour
when heated or cooled
Uses
– Warming of a hot cap
– Use in electric kettles
Phosphorescent Pigments
Phosphorescent pigments can glow in the
dark
They absorb and store energy and release it
as light over a period of time
They are much safer than alternative
radioactive substances
Examples – use in glow in the dark watches
Limestone and Marble
Limestone and marble are both forms of calcium
carbonate
Limestone is a sedimentary rock
Marble is a metamorphic rock made by the action of
high pressures and temperatures on limestone
Granite is an igneous rock
Marble is much harder than limestone
Granite is harder than marble
Limestone thermally decomposes to make calcium
oxide and carbon dioxide
Cement
Cement is made when limestone and clay are heated
together
Concrete
Concrete is made when cement, sand or gravel and
water are mixed together and allowed to set
Concrete can be reinforced, which is made by
allowing the concrete to set around a steel support
Reinforced concrete is a better construction material
than non reinforced because:
– Hardness of the concrete
– Flexibility and strength of the steel
C2
Does the earth move?
Metals and Alloys
Earth’s structure
The earth is a sphere with a thin rocky crust,
mantle and core
The earth’s core contains iron
The movement of tectonic plates results in volcanic
activity and earthquakes
Lithosphere
The outer layer of the earth is called the
lithosphere.
It includes the crust and outer part of the
mantle
It is described as oceanic plates under
oceans and continental plates forming
continents.
The lithosphere is cold and rigid
Tectonic plates
Tectonic plates are found on top of the
mantle because they are less dense than the
mantle
Energy transfer involving convection
currents in the largely solid mantle causes
the plates to move slowly.
Oceanic plates are more dense than
continental plates
Collision between oceanic and continental
plates leads to subduction and partial remelting (oceanic goes underneath
continental)
Volcanoes
Igneous rock is made when molten rock
cools down
Magma is molten rock beneath the surface
of the earth
Lava is molten rock that erupts from a
volcano
Some rocks on the earth’s surface have been
formed by volcanic activity
Some volcanoes give runny lava, some give
thick lava violently and catastrophically
Some people choose to live near volcanoes
because volcanic soil is very fertile
Magma
Magma from the mantle must have a density
less than that of the crust in order to rise
through it.
Igneous Rock
The size of crystals in an igneous rock is
related to the rate of cooling of molten rock
Iron rich Basalt and Gabbro are _____ crystals
______ cooling
Silica rich Rhyolite and Granite are ______ crystals
______ cooling
Geologists
Geologists study volcanoes to be able to
predict future eruptions and to reveal
information about the structure of the earth
Copper
Copper can be extracted by heating its ore with
carbon
Copper can be purified by electrolysis
Recycling copper is cheaper than making
copper and it saves resources
Problems of recycling copper:
Alloys
Alloy is a mixture of two elements one of
which is a metal
Eaxmples of alloys:
– Brass – copper and zinc
– Bronze
– Solder – lead and tin
– Steel
– Amalgam - mercury
One important large scale use for:
– Amalgam –
– Brass –
– Solder –
Properties of an alloy
The properties of an alloy are different from the
properties of the metals from which it is made
This makes alloys more useful than the pure
metal
– Steel is harder and stronger than iron
– Steel is less likely to corrode than iron
Metals
Metals are
– Hard
– High density
– High boiling and melting point
– strong
Homework
Explain how the use of ‘smart alloys’ such as
those with a shape memory property have
increased the number of applications of alloys
e.g. nitinol (nickel and titanium).
C2
Cars for Scrap
Clean Air
•
Rusting
Rusting needs iron, water and oxygen
It is an oxidation reaction where iron reacts
with water and oxygen to form hydrated iron
III oxide
Iron + oxygen + water → hydrated iron III
oxide
Aluminium does not corrode in moist
condition because it has a protective layer of
aluminium oxide which does not flake off
Salt water and acid rain accelerate rusting
Similarities and differences between iron and
aluminium
Iron is more dense than aluminium
Iron is magnetic and aluminium is not
Iron corrodes easily and aluminium does not
Iron and aluminium are both malleable
Iron and aluminium are both good electrical
conductors
Materials needed to build cars
Steel
Copper
Aluminium
Glass
Plastics
Fibres
Advantages and disadvantages of building cars
from aluminium or iron
Car body of the same car will be lighter with
aluminium
Car body with aluminium will corrode less
Car body will be more expensive made from
aluminium
Advantages of recycling materials
Saves natural resources
Reduces disposal problems
New laws will soon specify that a minimum
percentage of all materials used to
manufacture cars must be recyclable
•
•
•
Air contains oxygen, nitrogen, water vapour
and carbon dioxide
Oxygen, nitrogen and carbon dioxide levels in
the air are quite constant
Photosynthesis decreases the level of carbon
dioxide and increases the level of oxygen
Respiration and combustion increase the level
of carbon dioxide and decreases the level of
oxygen
Composition of air
21% oxygen
78% nitrogen
0.035% carbon dioxide
Deforestation


Increased energy consumption
(burning of fossil fuels)
Populations
How the present day atmosphere evolved
Original atmosphere came from gases
escaping from the interior of the earth
Photosynthesis by plants increases the
percentage of oxygen until it reached today’s level
Theory for how the atmosphere evolved
Degassing from the earth’s crust
Initial atmosphere of ammonia and carbon
dioxide
Formation of water
Development of photosynthetic organisms
Common pollutants
 Carbon monoxide – a poisonous gas.
Formed by the incomplete
combustion of petrol or diesel in car
engines
 Oxides of nitrogen – photochemical
smog and acid rain. Formed in the
internal combustion engine
 Sulphur dioxide – formed when
sulphur impurities in fossil fuels burn
 Acid rain will kill plants, aquatic life,
erode stonework and corrode metals
Catalytic converter
A catalytic converter removes carbon
monoxide from the exhausts gases of a motor
car by turning it into carbon dioxide
2CO + 2NO → N2 + 2CO2
C2
Faster and Slower
Reactions
Some reactions can be fast and others slow
 Rusting is a slow reaction
 Burning and explosions are fast reactions
Chemical Reaction
A chemical reaction takes place when particles collide
The more collisions between particles the faster the
reaction
Rate of a reaction
The rate of a reaction depends on the
 Collision frequency of reacting particles
 Energy transferred during the collision (whether
the collision is successful or effective)
Temperature
The rate of a chemical reaction can be increased
by increasing the temperature
Temperature increase makes particles move
faster so they have more energy. This results in
more effective, successful or energetic collisions
Concentration and Pressure
The rate of a chemical reaction can be increased
by increasing the concentration because the
particles are more crowded and this increases the
frequency of collisions between particles.
The rate of a gas phase reaction can be increased
by increasing the pressure
Graphs
Deciding when a reaction has finished
Recognising the fastest reactions – steeper graph
Recognising shortest reactions
Rate of a reaction can be calculated from the
slope of a graph
Reactions
A reaction stops when one of the reactants is
used up
The amount of product formed depends on the
amount of reactant used
Catalyst
Rate of a reaction can be increased by the
addition of a catalyst
A catalyst speeds up the rate of a reaction and is
unchanged at the end of the reaction
Only need a small amount of catalyst to catalyse
large amounts of reactants.
A catalyst is specific to a particular reaction
Surface Area
The rate of a reaction can be increased by using
powdered reactants rather than a lump
Powder has a larger surface area than a lump and
so reacts faster because there are more collisions.
Explosives
An explosion is a very fast reaction which
releases a large volume of gaseous products
– Custard powder
– TNT
– Dynamite