1. metals and alloys

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?



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?



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.



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.



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?



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.



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?



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.



Rate of corrosion experiment


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Are some metals easier to find than others?

Finding metals



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.



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



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.



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.



Extraction quiz



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 ?



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

1. metals and alloys

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