Metals and their uses

Mining for metals

What do I need to know

MustDiscuss the financial benefit and expense of obtaining metalsShouldDescribe how ores and metals are minedCouldExplain that reactive metals need a chemical reaction to turn them into the metal

What is a metal?

hard, shiny, porous, ductile, malleable,conducts electricity, insolublecan be hammered into shapeDuctile – means it can be pulled into wiresMalleable – means it can be bent into shape

These are the key properties of metals.

What is an ore?

• A metal ore is the rock that contains the compound that the metal is found in.

• It looks very different to the metal. • It is not usually native metal but a compound

such as iron oxide, copper oxide or lead oxide.• The ore has different properties to metals. It

does not conduct electricity and cannot be hammered into shape.

Mining

• Ores are extracted from the earth using mining and quarrying.

• This can cause damage to the environment if open quarrying is used and may be noisy and dusty.

• There will also be lorries and trucks which produce carbon dioxide as they carry the mined ore away from the quarry or mine.

Test your understanding

Unreactive metals such as ______ are found in the Earth as the _______ itself.

Most metals are mined as ___________ called ores that require chemical reactions to _______ the metal.

[GOLD, COMPOUNDS, METAL, EXTRACT]

Metals from ores

Reactivity series

What do I need to know?

MustRecall the position of different elements on the reactivity seriesShouldDescribe how the position of an element on the reactivity series determines how to extract itCouldExplain that carbon is used in a blast furnace to reduce iron oxide to iron

Reactivity series

• All metal elements have a different reactivity.• Some such as sodium are very reactive even in

air.• Others such as gold are extremely unreactive

Recalling the reactivity series

Lead

Aluminium

Carbon

Zinc

Copper

Iron

Titanium

Magnesium

Sodium

Gold

More reactive

Less reactive

Extracting metals

• A metal can be extracted from a compound by reacting with an element higher up in the reactivity series.

• So for example copper is more reactive than silver.

• If we add copper metal to silver nitrate compound we make silver metal.

• This is called a DISPLACEMENT REACTION

Extracting iron

• Iron ore (haematite) is iron oxide.• To make iron we need to remove the oxygen.• This process is called REDUCTIONCopy down this equation and the symbol equation. Be able to balance this equation!

Iron oxide + carbon Iron + Carbon dioxide2Fe2O3 + 3C 4Fe + 3CO2

Extracting Iron from its ore

• Carbon is part of the reactivity series and is higher (more reactive) than iron.

• This means iron can be extracted from its ore using carbon.

• This takes place inside a BLAST FURNACE

Test your knowledge

Metals that are ______ reactive than carbon in the reactivity series can be ___________ from their oxides by _________ with ________.

Iron oxide is reduced in the _________ ________ to make iron.

[extracted, reduction, carbon, less, blast furnace]

Summary

Recall the position of different elements on the reactivity series

Describe how the position of an element on the reactivity series determines how to extract it

Explain that carbon is used in a blast furnace to reduce iron oxide to iron

Steelmaking and alloys

BOS Process

What do I need to know?

Recall that most iron is converted into steels.

Describe how steels are alloys since they are mixtures of iron with carbon.

Explain that alloys can be designed to have properties for specific uses.

Why make steel?

• Pure iron is relatively soft and not very strong.

• The iron from the blast furnace is very hard and brittle. It contains about 4% carbon and is used as cast iron.

• We need an iron that is in between these two extremes.

Basic oxygen steelmaking

Carbon steels can be made by the following processes:

• blowing oxygen into molten cast iron to remove most of the carbon as carbon dioxide;

then…• adding a calculated amount of carbon.

The BOS process

Test your knowledge

• _____ is made from cast iron by blowing _____ into a large vessel containing molten iron.

• Oxygen reacts with _____ in the iron to make carbon dioxide and carbon monoxide

• The steel has _____ carbon than cast iron.

• ____ _____ is added to cool the reaction.

[ OXYGEN, CARBON, STEEL, LESS, SCRAP IRON]

Alloys

• An alloy is a metal that contains other elements.

• Cast iron is an alloy

Alloys with carbon

• Low carbon steel is easily shaped (more bendy).

• High carbon steel is hard and brittle (strong but not easily shaped).

• Look at the diagrams and see if you can work out why.

Hardness and tensile strength

• Carbon atoms get in the way of the iron atoms making the steel harder and less malleable.

• The strength of the steel is also affected by the amount of carbon in the steel. We call this the TENSILE STRENGTH.

• It is important to get the right balance between HARDNESS AND TENSILE STRENGTH.

Why alloy?

To change the properties for example to be:• harder• stronger• rust less or not at all• lighter• heavier• a different colour

Stainless steel

• This is an example of a very useful alloy of iron. It contains lots of different elements in small amounts.

• The most important addition is chromium and this stops the metal from rusting.

Other alloys

Most metals in everyday use are alloys. Pure copper, gold, iron and aluminium are too soft for many uses and so are mixed with small amounts of similar metals to make them harder.

Why recycle?

You need to know three main reasons:

• Preserve raw materials and ores• Save the energy used extracting new metal

from its ore• Reduce the waste going to landfill.

Extracting reactive metals

Reduction of metals high in the reactivity series

What do I need to know?

Recall that elements below carbon in the reactivity series can be reduced from their ores using carbon in a furnace.

Describe how more reactive metals can be obtained using electrolysis.

Explain why this means that aluminium and titanium are expensive metals to obtain and how important it is to recycle them.

Recalling the reactivity series

Lead

Aluminium

Carbon

Zinc

Copper

Iron

Titanium

Magnesium

Sodium

Gold

Titanium manufacture

• Can you select a metal that could extract titanium from its ore?

• In practice magnesium is used.• http://www.youtube.com/watch?v=XsdRo5jvn

Xo&feature=related• This means that titanium is incredibly

expensive due to the many stages required.

Test your understanding

1. What is the chemical process called when you obtain a metal from its ore?

2. Which metal is used to extract titanium?3. Why is titanium so expensive?

Titanium Manufacture

1. What is the chemical process called when you obtain a metal from its ore?– Reduction

2. Which metal is used to extract titanium?– Magnesium

3. Why is titanium so expensive?– The process takes a long time, uses expensive

raw material, uses a lot of energy and manpower.

Aluminium and electrolysis

• Aluminium is extracted using ELECTROLYSIS.• In electrolysis an electric current is used to

reduce the aluminium when it is in molten bauxite (aluminium oxide)

• Cryolite is added to lower the melting point of bauxite so it can be more easily melted.

Aluminium and electrolysis

• Aluminium is formed at the negative electrode or cathode

Test your knowledge

1. What is the method used to extract aluminium called?

2. What substance is added to help make the aluminium ore (bauxite) molten?

3. Which electrode (positive or negative) does the aluminium form at?

4. Why is making aluminium expensive?

Test your knowledge

1. What is the method used to extract aluminium called? REDUCTION BY ELECTROLYSIS

2. What substance is added to help make the aluminium ore (bauxite) molten? CRYOLITE

3. Which electrode (positive or negative) does the aluminium form at? NEGATIVE CATHODE

4. Why is making aluminium expensive? HIGH ENERGY COST TO MAKE ORE MOLTEN. ENERGY USED FOR ELECTROLYSIS

Why do we bother?

• If electrolysis for aluminium and the extraction of titanium with magnesium are so expensive then why not just use steel?

• Aluminium and titanium are valuable metals because of their properties.

• Aluminium is light and does not rust• Titanium is hard and has a very high melting

point.

Copper mining and extraction

• Copper sulfide ore can be dug up (mined) via traditional means

• Copper sulfide ore is turned into copper oxide. This produces sulfur dioxide (SO2) that can contribute to acid rain.

• Copper oxides is then smelted (burned in a furnace) with carbon.

• This reduces the copper ore to copper in a similar way to the blast furnace for iron, by reacting with carbon to remove the oxygen as CO2.

Copper electrolysis

• Copper is present in the solution as Cu2+ ions.• These positively charged copper ions move to

the negatively charged CATHODE • Here they gain electrons to become Cu or

Copper which builds up on the negative electrode.

• This purifies the copper as other impurities do not travel to the cathode to be deposited.

Copper purification

Problems with traditional copper mining

• Copper is extracted from its ores by chemical processes that involve heat or electricity;

• this contributes to greenhouse gases and global warming.

• copper-rich ores are being depleted; and• traditional mining and extraction have major

environmental impacts.

Bioleaching

• Copper can also come from bioleaching• Bioleaching is the extraction of copper from its

ore through the use of living organisms (bacteria).

• This is much cleaner than the traditional leaching using cyanide or smelting as no greenhouse gases are produced from burning coal.

Phytomining

• Phytomining involves using plants to extract the metal compounds present in copper rich soils.

• Once the plants have been grown they are burned to produce ash that contains the metal compounds.

• The metal can then be extracted using electrolysis.

• This is cleaner and less polluting.

Summary

Recall that elements below carbon in the reactivity series can be reduced from their ores using carbon in a furnace.

Describe how more reactive metals can be obtained using electrolysis.

Explain why this means that aluminium and titanium are expensive metals to obtain and how important it is to recycle them.

Transition metals

Uses and properties

What do I need to know?

MustRecall the general properties of metals and how they differ from non metalsShould Describe how the uses of metals are determined by their propertiesCould Identify where transition metals are found on the periodic table and identify three examples.

Transition metals

Transition metals are found in the middle section of the periodic table.

Find this section on the periodic table in your planner and write down at least three examples of transition metals you have heard of. Two examples are gold, Au and iron, Fe.

Some transition metals are very rare and very valuable.

Identifying transition metals

Circle the elements you think are transition metals.

IRON, COPPER, CARBON, SODIUM, TUNGSTEN, LEAD, NICKEL

Uses of transition metals• Gold – precious metal, rare so very expensive yellow and shiny,

used for jewellery and electrical contacts• Platinum – precious metal, rare so very expensive, silvery, shiny,

used for jewellery• Iron – available in large quantities, strong, hard and high tensile

strength, can be made corrosion resistant, used in building• Copper – high electrical conductivity, ductile (can be made into

wires), malleable (can be made into pipes), used in electrical wires and plumbing. Has coloured compounds.

• Zinc – corrosion resistant when galvanised or oxidised, can be given an attractive finish, used in dustbins, wheelbarrows and other outdoor applications.

• Tungsten – very high melting point, ductile and high tensile strength, used in lightbulb filaments.

Complete the table

Property Use Example metal

Good conductor of electricity

Used to make electrical wires

Copper

Shiny Used to make mirrors and jewellery

Silver

Good conductor of heat

Dense

Strong

High melting point

Magnetic

The first two have been done for you

Test your understanding

Copper is used to make the electrical wires in our houses. Silver is an even better conductor of electricity than copper.

Why don’t we use silver to make the wires for the electric circuits in our houses?