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Module 2
Rock Cycle
Metals
The Air
Uses of Metals
Iron is used for girders,
transport and cutlery.
Copper is used in coinage,
water pipes, electrical
wiring and ornaments.
Aluminium is used for
window frames,
aircraft and pans.
Extracting Metals from Ores
REACTIVITY
SERIES
METHOD OF EXTRACTION
Sodium
Calcium
Magnesium
Aluminium
Carbon
Zinc
Iron
Copper
Energy is required to extract them from
their ores, because they are very
reactive. ELECTROLYSIS is used. Metals
are formed at the cathode.
The most reactive
metals are most
difficult to extract
from their ores.
These metals are below carbon in the
reactivity series and are extracted by
heating with carbon/carbon monoxide.
Gold
Platinum
The least reactive
metals are the
easiest to extract
from their ores.
These metals are unreactive and exist
NATURALLY. They are obtained by
physical processes, eg panning.
REDUCTION
• Reduction is the loss of oxygen from a compound.
Copper oxide
+
Carbon
heat
REDUCTION
Copper
+
Carbon dioxide
Purification of copper and half-equations.
• The anode is made of impure copper and the cathode
is made of pure copper.
• At the anode (+) copper ions pass into solution.
• At the cathode (-) copper atoms are deposited.
• The solution must contain copper ions and is usually
copper (II) sulphate.
Half Equations.
The reactions at the electrodes can be written as half-equations. This means that
we write separate equations for what is happening at each of the electrodes during
electrolysis.
For the purification of copper by electrolysis.
At the CATHODE (-):
Cu2+
Blue copper (II) solution
At the ANODE (+):
Cu
Copper metal
+
2e-
gains two electrons
OXIDATION
Cu
REDUCTION
Cu2+
blue copper (II) solution
pinky brown copper metal
+
2eloses two electrons
The solution of copper sulphate does not alter in concentration during the process, if
everything is working as it should. The copper atoms change to copper(II) ions and leave
the anode to go into solution at just the same rate that copper (II) ions arrive at the
cathode and change into copper atoms.
TRANSITION METALS
TRANSITION METALS
In general the transition
metals…
• have high melting points
• have high densities
• are good conductors of
electricity and heat
• often form coloured
compounds
Some of them are in
common use eg. Wires,
pans,girders, ornaments,
cars, jewellery.
Rocks, classify
the following
rocks;
Rocks and the Rock Cycle
GRANITE
IGNEOUS
LIMESTONE
SLATE
BASALT
1
MARBLE
2
4
5
Features;
Features;
Features;
grainy
usually
and
hard
crumbly
rocks
a ahard
rock
consisting
containing
which
tinysometimes
crystals
ofrock
interlocking
crystalson
cooling,
contains
could
fossils
contain
by
which
are large
if
the
which
distorted
thecooled
fossils.
rock can
They
be
rock
has
slowly
are chemically
and smallidentical
if dated
it hasto
thecooled
rocksquickly.
they are
formed from.
SANDSTONE
3
METAMORPHIC
SEDIMENTARY
6
Process 1 & 5 - the rock melts to form MAGMA, which wells up from the
Process
2 and
&4
6 COOLS
-- made
from
ofbyABOVE
SEDIMENT
whose weight
squeezes
out
MANTLE
DOWN
either
or TEMPERATURE
WITHIN
the Earth’s
crust.
Process 3
&
the rock
is layers
formed
extreme
and PRESSURE
WATER
causing
particles
to becomeprocesses
CEMENTED
together,
YOUNGER rocksrocks
caused by
MOUNTAIN
BUILDING
which
force SEDIMENTARY
therefore
are usually
deep underground
nearontotop.
MAGMA where they are COMPRESSED and HEATED
changing their TEXTURE and STRUCTURE. They can be formed from any rock
type.
The Earth’s Atmosphere.
4 billion
years ago
O2
Rest
N2
CO2
Present
day
2.5 billion
years ago
O2
CO2
Rest
CO2
N2
Primitive green plants evolve and
• The oxygen in the atmosphere is now much increased
Volcanic activity releases
•CARBON DIOXIDE is reduced as plants
• Some
take of
it in
it and
is converted to OZONE which protects
• mainly CARBON
release OXYGEN
animals from the full extent of the Sun’s UV radiation.
DIOXIDE, and
New species evolve.
•
microorganisms
which
can’t
tolerate
OXYGEN
die off
• smaller amounts of
• There is a state of balance because
hydrogen, carbon
• carbon from CARBON DIOXIDE is locked up in sedimentary
monoxide and nitrogen rocks as carbonates and fossil fuels. Carbonates
• PHOTOSYNTHESIS
are formed produces oxygen in sunlight.
with
as a result of carbon dioxide dissolving in the oceans.
• RESPIRATION and BURNING FUELS use oxygen and
• WATER VAPOUR which
• More NITROGEN is added to the atmosphere
produce carbon
as a result
dioxide.
of
condenses as the EarthDENITRIFYING BACTERIA on nitrates from decaying plant
• Carbon dioxide is absorbed by the SEAS and OCEANS
cools to form the oceans
.
materials
.
Limestone, Thermal Decomposition and
limewater
Limestone is mainly Calcium Carbonate.
When slaked lime is
dissolved in water,
limewater is produced.
Calcium Carbonate
CaCO3
Limewater reacts with
carbon dioxide to form
Calcium carbonate.
This is the test for
Carbon dioxide.
Carbon dioxide
CO2
Calcium hydroxide
Ca(OH)2
It can be used as a
neutralising agent.
It is used in glass making,
cement making and in the
Blast furnace
It is decomposed by heat
to form calcium oxide, also
known as quicklime.
Calcium Oxide
CaO
When water is added to
quicklime, slaked lime is
produced.
Both these products can be used
to neutralise acid in soils.
Limestone
• Limestone is a sedimentary rock.
• It comes from the shells of sea creatures or from
solids formed in the oceans long ago.
• It is mostly made of calcium carbonate - CaCO3.
• It is an important raw material for both the
chemical and the construction industries.
Limestone for soil
Limestone is used in agriculture.
• Acidity can build up in soils.
• This can inhibit the growth of many crops.
Consequently farmers need to adjust the pH
back towards neutral.
• Limestone provides a cheap way of
neutralising soil acidity.
pH
5
6
7
Limestone - extraction of iron
In the blast furnace limestone removes acidic earthy
impurities that would ruin the quality of iron.
• Limestone is one of three major raw
materials used to extract iron from its ores.
• It reacts with acidic impurities changing
them into a slag that separates from the
iron.
CaCO3 +
SiO2
CaSiO3 + CO2
Quicklime - the lime kiln
• Limestone is heated in huge ovens
known as lime kilns.
• The calcium carbonate
decomposes into calcium oxide
(quicklime) and carbon dioxide.
• Quicklime is a vital ingredient of
cement, concrete and of most
types of glass.
CaCO3
CaO
+ CO2
Slaked lime
• If water is added to quicklime the calcium oxide
changes into calcium hydroxide (slaked lime).
• Slaked lime is a vital ingredient of various building
materials.
CaO
+ H 2O

Ca(OH)2
• A solution of calcium hydroxide (limewater) is
also used to test for carbon dioxide gas (it goes
cloudy).
Manufacture of cement
• The main raw materials for cement are
limestone and clay.
• A small amount of gypsum is also added to
help the cement set at the right speed.
Limestone
or chalk
heat
Cement
Clay or
shale
Gypsum
(calcium sulphate)
Cement, concrete and mortar
• To make concrete cement is mixed with small
stones or gravel.
• Mortar consists of cement mixed with calcium
hydroxide. This makes a smooth slow setting
mixture suitable for bricklaying
Cement, concrete and mortar all set
when interlocking crystals grow between
cement particles joining them together.
Manufacture of glass
Limestone, sand and sodium carbonate are the
raw materials used to make most glass.
Sodium
carbonate
Glass
Limestone
heat
water
Lime
(calcium
hydroxide)
Sand (silicon
dioxide)
heat
Match it up