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We are covering
From C1
Limestone
Extracting Metals
Crude Oil
Alkanes
Alkenes
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Where do building materials come from?
glass is made from sand and limestone
bricks are made from clay
cement is made from limestone or clay.
Buildings are constructed
using materials from the Earth.
Some ‘cut rocks’, including
granite, marble and limestone,
make excellent building
materials.
Changing or combining rocks
from the Earth provides other
useful materials:
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What is limestone?
Limestone is an attractive pale yellow or grey stone.
Limestone is used during the
production of other building
materials including:
cement
concrete
It is also used to extract impurities from iron in a blast
furnace, which produces a useable metal from iron ore.
mortar
glass
Blocks of cut limestone are
used as a material for buildings
and statues.
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Cement is used as a binder in concrete and mortar.
What is cement?
It is made by heating limestone or clay
and adding gypsum (a compound from
limestone). This mixture is then ground
into a powder.
Mortar is made from cement, water
and sand. It is used in bricklaying and
stonework.
An even layer of mortar is spread
between the bricks or stones to hold
them firmly together.
After the powder is mixed with water,
it will harden to form a strong glue.
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What is reinforced concrete?
Although concrete is a very hard material, it is not very
flexible. This means that when it is stretched it can break.
Concrete has a low resistance to tension forces.
Steel rods are used to increase the
strength and flexibility of concrete.
This is called reinforced concrete.
This material can support 300 to
500 times the combined mass of
steel and concrete it is made from.
Reinforced concrete has many
uses, including lamp-posts,
railways and as a structural
material to support buildings.
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How is concrete made?
Concrete is made from sand,
cement and water but it is
harder than mortar because
it also contains gravel.
What is the word equation for making concrete?
Concrete is harder than mortar. It is sometimes described
as an artificial rock.
It is used for the foundations
of buildings and for large
structures, such as car parks.
cement sand water concrete + + gravel +
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When limestone is heated strongly, a
chemical reaction takes place. Calcium
carbonate breaks down and forms calcium
oxide and carbon dioxide. This type of
reaction is called thermal decomposition.
Limestone is a valuable material because it can be used as
the starting point for many other materials.
calcium carbonate
calcium oxide
carbon dioxide +
What is thermal decomposition?
A lime kiln is often used for this reaction.
The limestone is heated to 900 °C. This
method has been used for centuries.
What is the word equation for this reaction?
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magnesium carbonate
magnesium oxide
carbon dioxide +
What about other metal carbonates?
Other metal carbonates can decompose in a similar way to
calcium carbonate, when they are heated.
metal carbonate
metal oxide
carbon dioxide +
What products are formed when copper carbonate
decomposes on heating?
The general equation for the thermal decomposition of a
metal carbonate is:
For example, when magnesium carbonate is heated it
breaks down to form magnesium oxide and carbon dioxide.
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The chemical name for slaked lime is calcium hydroxide.
How is slaked lime made?
calcium oxide
water calcium hydroxide +
What is the word equation for this reaction?
Uses of slaked lime include glass manufacture
and neutralization of the effects of acid rain.
Quicklime is used as an industrial drying
agent and to make slaked lime.
Calcium oxide, a product of the thermal
decomposition of limestone, is also
called quicklime.
Slaked lime is made by adding water to quicklime.
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Why does carbon dioxide turn limewater cloudy?
Fully dissolving calcium hydroxide in water forms limewater.
Limewater is used to test for carbon dioxide.
When carbon dioxide gas is bubbled through
limewater, the limewater becomes cloudy.
The carbon dioxide reacts with calcium hydroxide
to form calcium carbonate and water.
The solid calcium carbonate is held in suspension,
which gives the limewater a cloudy appearance.
What is the word equation for this reaction?
calcium carbonate
calcium hydroxide (aq)
carbon dioxide + + water
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Summary of uses of limestone products
Slaked lime, calcium hydroxide, is used to
make the building materials mortar and glass.
Slaked lime is alkaline. It can be sprayed on
agricultural fields to reduce soil acidity and
on lakes to neutralize the effects of acid rain.
Quicklime, calcium oxide, is used in making
steel and as an industrial drying agent. It can
be mixed with water to form slaked lime.
Limewater is made by fully dissolving slaked lime
in water. It is often used to test for carbon
dioxide. This is because limewater turns cloudy
in the presence of carbon dioxide.
The products of limestone have many uses.
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Limestone and its products can be involved in various useful
chemical reactions:
Summary of limestone chemistry
calcium oxide
water calcium hydroxide +
calcium carbonate
calcium oxide
carbon dioxide +
thermal decomposition of limestone
production of slaked lime
using limewater to test for carbon dioxide.
calcium carbonate
calcium hydroxide (aq)
carbon dioxide + + water
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How does quarrying affect the environment?
Limestone is an essential
building material. Millions of
kilograms of limestone are
extracted every year for use in
construction and industry.
However, quarrying limestone
can cause environmental
damage.
Limestone is often found in areas of outstanding natural
beauty. Quarrying can leave scars on the landscape.
Explosives used in quarrying produce noise and dust.
Air and noise pollution is caused by lorries transporting
limestone from the quarry.
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Impacts of limestone quarrying
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There are two main ways of extracting metals from their ores:
burning ores with carbon (reduction)
electrolysis
How do mining companies decide which method to use?
Gold and other unreactive metals occur
native. Metals that are found in the ground
as uncombined elements do not require
further extraction.
What methods are used to extract metals?
Most metals are found combined with other elements, as
compounds in ores. These metals need to be separated
from the other elements that they are combined with using
chemical reactions.
Extraction methods vary for different metals.
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Metals are often found combined with oxygen as oxides.
To obtain the metal, the oxygen must be removed.
In this reaction, the carbon removes oxygen from lead oxide.
This occurs because carbon is more reactive than lead.
What is reduction?
The removal of oxygen from a substance is called reduction.
Carbon can be used to extract metals by reduction.
lead oxide + carbon lead carbon
monoxide +
PbO C Pb CO + +
metal oxide (in ore) metal reduction
The addition of oxygen to a substance is called oxidation.
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Reactions of metal oxides and carbon
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Extracting iron in industry
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Which metals does carbon reduce?
A metal can be reduced by carbon if it
is less reactive than carbon and so
appears below carbon in the reactivity
series.
Using the reactivity series, can you name
a metal that cannot be extracted from its
ore using carbon?
If a metal is more reactive than carbon,
other chemical reactions and processes
must be used in its extraction.
Certain metals, such as iron, can be
only be reduced using carbon if they
are heated to very high temperatures.
potassium sodium calcium
magnesium aluminium
zinc iron
copper
gold
lead
silver
(carbon)
(hydrogen)
platinum
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How can the impacts of extraction be reduced?
New mining techniques can decrease the effects of metal
extraction on the environment.
Leaching uses less electricity than traditional
mining and does not produce waste gases.
Copper ores are treated with and dissolved in
dilute sulfuric acid, producing copper sulfate.
Electrolysis is then used to extract the copper.
Certain bacteria can also be used to dissolve
ores and form copper sulfate.
Phytomining uses plants to absorb metals
from the soil. The process can be used to
clean contaminated land. Treating the plants
with certain chemicals increases their ability
to accumulate minerals in their cells.
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How can recycling help?
Recycling creates less waste and reduces
the number of sites that have to be mined.
Recycling uses up to 95% less electricity
than producing metals from ores.
Metals are easier to recycle than plastic and they retain
their original properties, such as conductivity and hardness.
Recycling costs less than extracting
metals and can be profitable.
One problem is that metallic materials in recycled objects are
often mixtures of different metals. This can mean that
obtaining pure metals from recycling is more expensive, as
it may use more electricity than extracting metals from ores.
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What is crude oil?
Crude oil is a fossil fuel and one of the most important
substances in the world. It is a mixture of hundreds of
different compounds.
Crude oil is used to make
fuels for transport, heating
and generating electricity.
It is also used to make
plastics and hundreds of
different types of chemicals.
Every day, the world uses over 70 million barrels of oil. If you
filled bath tubs with this amount of oil and put them end-to-
end, they would stretch round the Earth 7.5 times!
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How was crude oil made?
Crude oil is thought to have been
made from the remains of marine
plants and animals that died
millions of years ago.
These remains sank to the
bottom of the sea, where they
were buried in layers of sand and
mud, preventing them from rotting. These
layers gradually became sedimentary rock.
Over millions of years the layers of rock built up, increasing
the heat and pressure. This caused the remains to be broken
down into the molecules that form crude oil and natural gas.
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Hydrocarbons in crude oil
Many compounds in crude oil only contain the elements
carbon and hydrogen. They are called hydrocarbons.
Most hydrocarbons in crude oil are compounds called
alkanes. Alkanes contain a single chain of carbon atoms
with hydrogen atoms bonded along the side.
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What are alkanes?
Alkanes are a family of hydrocarbon compounds with the
general formula CnH2n+2.
The simplest alkane is methane.
It has the formula CH4.
The second simplest alkane is
ethane. It has the formula C2H6.
The third simplest alkane is
propane. It has the formula C3H8.
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Finding crude oil at sea
Crude oil is often found trapped in rocks of the sea bed.
Oil rigs or drilling
platforms are used to
drill through the sea
bed to obtain the oil.
Once the oil has been
removed from the sea
bed, it is pumped in long
pipelines to an oil tanker
terminal or an oil refinery
on land.
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Problems with crude oil
Crude oil is extremely useful but it has several drawbacks:
Burning the products of crude oil as fuel produces gases
and particles that contribute to global warming and air
pollution.
Removing oil from the
ground, as well as oil
spillages and slicks, can be
very damaging to wildlife
and the environment.
The high value of oil means it is sometimes the cause of
military conflict, especially because a large amount of oil
comes from countries that are politically unstable.
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Crude oil itself has no uses – it must first be processed or
refined. This is done in an oil refinery.
The first step is to
separate
compounds in the
oil into groups
called fractions.
Each fraction
contains a mix of
compounds with
a similar number
of carbon atoms.
How can crude oil be made useful?
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Molecule size and boiling point
The more carbon atoms in a hydrocarbon molecule, the
larger the molecule. How does this affect its boiling point?
Generally, the larger a hydrocarbon,
the higher its boiling point.
This is because the intermolecular forces between large
molecules are stronger than the intermolecular forces
between small molecules.
More energy is needed to break the forces between large
molecules, and so the boiling point is higher.
Molecules in crude oil can contain anything from just
1 carbon atom to well over 50.
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What is fractional distillation?
Fractional distillation is a process used to separate a
mixture of liquids that have different boiling points.
Fractional distillation is used to separate
crude oil into fractions with different
boiling points. It can be done industrially
and in the laboratory.
When the mixture is heated, liquids with a low
boiling point evaporate and turn to vapour.
Liquids with a higher boiling point remain
as liquid. The vapour can then be
separated from the liquid.
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Fractional distillation of crude oil
Crude oil is separated into fractions by fractional distillation.
1. Oil is heated to about 450 °C and pumped
into the bottom of a tall tower called a
fractionating column, where it vaporizes.
2. The column is very hot at the bottom but
much cooler at the top. As the vaporized oil
rises, it cools and condenses.
3. Heavy fractions (containing large molecules)
have a high boiling point and condense near
the bottom of the column.
4. Lighter fractions (containing small molecules)
have a lower boiling point and condense
further up the column.
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How does fractional distillation work?
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Order of fractions
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Supply and demand
The amount of each type of fraction obtained by fractional
distillation does not usually match the amount of each
fraction that is needed.
Crude oil often contains more
heavier fractions than lighter
fractions. Lighter fractions are
more useful and therefore
more desirable.
The large hydrocarbon molecules
in the heavier fractions can be
broken down into smaller, more
useful, molecules to meet demand
for raw materials for fuels and plastics.
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Catalytic cracking
Large hydrocarbon molecules can be broken down into
smaller molecules using a catalyst. This is called catalytic
cracking, and is an example of a thermal decomposition
reaction.
The hydrocarbon molecules are
heated until they turn into
vapour, and then mixed with a
catalyst. The molecules break
apart, forming smaller alkanes
and alkenes.
Alkenes are reactive molecules
that are used to make plastics and
other chemicals.
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What are alkenes?
Alkenes are a family of hydrocarbon compounds with the
general formula CnH2n.
Alkenes are very similar to alkanes, but they have one
important difference: they contain at least one double
covalent bond between carbon atoms.
The simplest alkene is ethene.
It has the formula C2H4.
The second simplest alkene is
propene. It has the formula
C3H6.
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Cracking decane
Decane from the naphtha fraction can be cracked to form
pentane (for use in petrol), propene and ethene.
decane
(C10H22)
pentane
(C5H12)
propene
(C3H6)
ethene
(C2H4)
+ +
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Saturated vs. unsaturated
Alkanes are examples of saturated compounds.
Alkenes are examples of unsaturated compounds.
A saturated compound only contains single
covalent bonds between carbon atoms.
An unsaturated compound contains at least one
double covalent bond between carbon atoms.
A test to distinguish between saturated and unsaturated
compounds is to add red bromine water. In the presence of
unsaturated compounds, the red colour disappears.
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How does catalytic cracking work?
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Catalytic cracking in the lab
Catalytic cracking can be done in the laboratory by heating
mineral wool soaked in oil with a catalyst, producing a gas.
What might this gas be?
mineral wool
soaked in oil
gaseous product
aluminium
oxide catalyst
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The stages of fractional distillation
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What you need to do at home
Metals – their properties and what they are used for
Aluminium
Copper
Titanium
Iron and Steel
What an alloy is
What each is used for
What the differences are
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