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7/27/2019 1. Metals and Alloys
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How many different uses of metal can you spot?
What are metals used for?
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Why are metals important?
Metals are a highly valuable group of materials, used for
hundreds of products and produced in huge quantities.
35,500,000 tons of
aluminiumwere
produced in 2005.
The production ofcopperincreased by more than
20 times in the 20th century.
Goldis worth more than
10,000 per kilogram.
Metals have played a vital role in human development.
Periods of civilization are even classified by the metals
that were used during those times, such as the Iron Age.
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Using metals
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Uses of metals activity
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What else can metals be used for?
It is easy to find products made from metals, but there are
other uses of metals that are less obvious.
Compounds containing metals have many
uses. For example, metal compounds areused to colour materials including stained
glass and even make-up!
Can you find any other uses of metals?
Metals are used as catalysts to speed
up reactions. Nickel is used as a
catalyst to make margarine. Platinum
is used in catalytic converters in car
engines to clean up exhaust fumes
and reduce pollution.
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What decides what metals are used for?
It is not only the properties of a metal that determines its use.
What other factors might determine how metals are used?
For example, aluminium only became a
commonly used metal in the late 19th centuryas better extraction methods made it cheaper.
For example, silver is a better conductor than copper
but it is too expensive to be used for electric wires.
Cost. A metal may have the best propertiesfor a job but it might be too expensive.
Extraction method. This can greatly affect
the price and availability of a metal.
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What are the properties of different metals?
Do all metals behave in the same way?
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Metals are known to have certain properties:
solid at room temperature
high melting point
good conductors of electricity and heat
malleable: they can be hammered into sheets
ductile: they can be drawn into wires
strong
dense.
Why do metals have these particular properties?
What are the typical properties of metals?
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The properties of metals can be explained by examining
the structure of their atoms.
Metals have a lattice structure.
The atoms in a pure metal are
arranged in closely-packed
layers. This makes them strong.
The outer electrons of each atom
separate from the atom and
become delocalized. These form
a sea of electrons free to move
in the lattice, which allows metalsto conduct heat and electricity.
What is the structure of metals?
sea of electrons
lattice structure
The sea of electrons also produces strong bonds between
atoms. This is why metals have high melting points.
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When a metal is hit, the layers of atoms are able to move
over each other.
Why can metals be shaped?
Bonds between atoms are not broken because the electrons
are free to move, but the shape of the metal can be changed.
metal before it is hit metal after it is hit
forceforce
This behaviour is what makes metals:
malleable they can be shaped
ductile they can be drawn into wires.
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Corrosion is the gradual destruction of a metal due to
reactions with other chemicals in its environment.
Over time, corrosion changes
the appearance of the metal as
it breaks down and it becomes
weaker.
Corrosion can seriously damage
metallic objects and structures.
What is corrosion?
Coating the surface of a metal
with paint and certain chemicalscan protect it from corrosion.
What happens if the protective coating becomes damaged?
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Metals behave differently when exposed to the environment.
Items made from gold can
survive for thousands of
years and have even been
found in good conditionunderwater.
Do all metals corrode?
In many cultures, gold is
considered a precious metal
and is used to make sacred
and decorative objects.
Gold is an unreactive metal and does not corrode easily.
In general, objects made from metals that corrode easily,
do not survive for as long.
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coating of
oxygen atoms
The outer aluminium atoms react with oxygen in the
atmosphere. This forms a thin layer ofaluminium oxide on
the metals surface, which protects the metal from corrosion.
Aluminium is a very reactive metal. However, it does
not corrode in the presence of oxygen. Why is this?
oxygen in theatmosphere
aluminiumatoms
Why doesnt aluminium corrode?
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Rusting is the specific name
given to the corrosion of iron.
It is a chemical reaction between
iron, oxygen and water.
What is the word equation for the formation of rust?
hydrated iron oxideiron oxygen water+ +
Salt can increase the rate of rusting. This iron bolt is on a
seaside structure and is nearly completely corroded.
What is rusting?
The chemical name for rust is
hydrated iron oxide. Rust can
form on cars and buildings,making them unsafe. It is an
expensive problem.
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Rate of corrosion experiment
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Are some metals easier to find than others?
Finding metals
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Most metals are actually found combined with other elements,
as compounds in ores. These metals must be extractedfrom their ores before they can be made useful.
Metals can be found in the Earths
crust combined with other elements or
uncombined as pure substances.
Some unreactive metals, like gold,
silver and copper, can be found
uncombined as elements.
Where do metals come from?
Metals that are found in a pure form
are said to occur native.
Highly reactive metals, such as titanium, require complicatedextraction. This can increase the cost of the pure metal.
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potassiumsodiumcalcium
magnesiumaluminium
zinciron
copper
gold
incre
asingr
eact
ivity
Metals above carbon in thereactivity series must be
extracted using electrolysis.
Electrolysis can also be
used to purify copper.
Metals below carbon can
be extracted from their ores
by reduction using carbon,
coke or charcoal.
Platinum, gold, silver and
copper can occurnativeand
do not need to be extracted.
lead
silver
How does reactivity affect extraction?
The reactivity of a metal determines how it is extracted.
(carbon)
(hydrogen)
platinum
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Metals that are less reactive
than carbon can be extracted
from their ores by burning withcarbon.
Iron is extracted by this method
in a blast furnace. The iron ore
is heated with carbon-rich cokeat very high temperatures.
The iron collected from a blast
furnace is only 96% pure.
How is carbon used to extract metals?
molteniron
hot air
moltenslag
raw materials
Usually, this product needs to
be treated further because
the impurities make the iron
brittle.
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Metals that are more reactive than carbon are extracted
using electrolysis.
This process uses an electrical current to extract the metal.
Electrolysis is more expensive than using a blast furnace,
and this increases the price of the metal.
What is electrolysis?
Electrolysis is also used to
further purify metals, such
as copper, after extraction
with carbon.
Aluminium is extracted
from its ore, bauxite,
using this method.
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Extraction quiz
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Metals are easy to recycle and do not change their properties.
What are the benefits of recycling metals?
Saves energyRecycling aluminium uses 95% lessenergy than extracting it from its ores.
Uses less
resourcesReduceswaste
Less damage
to environment
Profitable
Recycling reduces the need to mine
sensitive areas for new ores.
Recycling one car saves over 1000 kg of
iron ore and over 600 kg of coal.14 million fewer dustbins would be filledper year by recycling aluminium in the UK.
Recycled copper can be resold for up to90% of what it was worth when new.
Can metals be recycled?
Wh h d b k f li ?
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What are the drawbacks of recycling?
Recycled copper is too impure
for electric wires. However, scrap
copper can be used in products,such as coins and ornaments,
that do not need pure metal.
Metallic materials are often mixtures of different metals.
Pure metals can be obtained by purifying recycled materials
but this can be expensive and may use more electricity thanextracting metals from ores.
Sorting mixed metals for recycling
can be difficult. Iron and steel(a mixture of iron with other
elements) are exceptions. These
materials can be separated from
waste using a magnet.
R li t ti ?
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Recycling or extraction?
G th t l ti it
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Guess the metal activity
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Wh t i ll ?
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An alloy is a mixture of a metal with at least one other
element.
Steel is a common example of an alloy. It contains iron mixed
with carbon and other elements. Adding other elements to a
metal changes its structure and so changes its properties.
The final alloy may havevery different properties
to the original metal.
By changing the amount
of each element in analloy, material scientists
can custom-make alloys
to fit a given job.
What is an alloy?
Wh t t f ll th ?
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What types of alloys are there?
Alloys have been used for thousands of years. Bronze, an
alloy of copper and tin, was commonly used by civilizations
before iron extraction methods were developed.
Other well-known alloys are:
brassan alloy of copper and zinc.
It does not tarnish and is used for door
knobs, buttons and musical instruments.
solder an alloy of zinc and lead.
It is used in electronics to fix
components to circuit boards.
amalgam an alloy of mercury with
silver or tin. It is used for dental fillings
because it can be shaped when warm
and resists corrosion.
I ld ll ?
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Although pure gold is sometimes used in electronics, gold
jewellery is always a mixture of gold and other metals.
Pure gold is actually quite soft. Adding small amounts of
other metals makes the gold hard enough to use in jewellery.
Alloying gold with different metals also affects its colour.
The familiaryellow gold is analloy of gold mixed with copper
and silver. Adding more copper
than silver gives redder shades.
White gold is an alloy of goldwith nickel, platinum or palladium.
Around 12% of people may be
allergic to the nickel in white gold.
Is gold an alloy?
Wh i i t i ?
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When is a copper coin not a copper coin?
When it is a copper-coated alloy!
Since 1992, UK copper coins have been made from
copper-plated steel and are magnetic. A magnet can be
used to separate copper coins by age.
Copper coins used to be made from
pure copper but most copper coins
used around the world are now made
from copper alloys.
Previously, as the value of copper
increased, the metal used to make
the coin became worth more than the
actual coins.A melted-down, pure
copper coin could have been sold for
more than the face value of the coin!
What is steel?
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Steel is an alloy of ironand other elements, including carbon,
nickel and chromium.
Steel is stronger than pure iron and can be used for
everything from sauce pans to suspension bridges!
What is steel?
Why is steel stronger than iron?
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The atoms of other elements
are different sizes. When otherelements are added to iron,
their atoms distort the regular
structure of the iron atoms.
The atoms in pure iron are
arranged in densely packed
layers. These layers can slideover each other. This makes
pure iron a very soft material.
Why is steel stronger than iron?
It is more difficult for the layers
of iron atoms in steel to slide
over each other and so this
alloy is stronger than pure iron.
What types of steel are there?
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Steel can contain up to 2% carbon.
Varying the amount of carbon gives
steel different properties. For example,
increasing the carbon content,
increases the hardness of the steel.
Different types of steel are classified
by how much carbon they contain:
low carbon steelcontains less than 0.25% carbon.
high carbon steelcontains more than 0.5% carbon.
Two other important types of steel are:
What types of steel are there?
stainless steel an alloy of iron that contains at least
11% chromium and smaller amounts of nickel and carbon.
titanium steel an alloy of iron and titanium.
Using different types of steel
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Using different types of steel
Using different types of steel activity
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Using different types of steel activity
Whats so clever about smart alloys?
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What s so clever about smart alloys?
Shape memory alloy is a type of smart material made from
metals that returns to its original shape after being deformed.
A smart material can change one or more of its physical
characteristics under the influence of an external stimulus.
Nitinol is a type of shape
memory alloy made from
nickel and titanium.
This material can be used
to make a pair of glasses
that remembers its shape
and does not break when
crushed.
Nitinol has also been used to hold badly broken bones
in place whilst they heal.
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Glossary (1/2)
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Glossary (1/2)
alloy A mixture of a metal with at least one other element.
amalgam An alloy of mercury that is used for dentalfillings.
blast furnace A tall oven used to extract iron from ironore by burning it with carbon at high temperatures.
brass An alloy of copper and zinc that is used forornaments.
corrosion The destruction of a metal caused byreactions with chemicals in the environment.
ductile The ability of metals to be drawn into wires. electrolysis A process that uses electricity to extract or
purify metals.
Glossary (2/2)
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Glossary (2/2)
malleable The ability of metals to be bent or hammeredinto different shapes.
native The natural occurrence of a metal as an elementin the environment.
ore A rock that contains a metal combined with otherelements in concentrations that make it profitable to mine.
rusting The specific name for the corrosion of iron andiron-containing alloys, such as steel.
shape memory alloy A type of alloy that can return toits original shape after being deformed.
solder An alloy of lead and tin that is used in electronics.
steel An alloy containing iron and other elements.
Anagrams
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Anagrams
Multiple-choice quiz
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Multiple-choice quiz