Production and Uses of Production and Uses of MetalsMetals

CHEMISTRY 2CHEMISTRY 2

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Metallic mineralsMetallic minerals

Pyrite

(a mineral of iron - sulphide)

Haematite

(a mineral of iron - oxide)

The least reactive metals occur in an uncombined form within the Earth’s crust.

The other metals exist as ores in combination with other elements such as oxygen and sulphur.

Iron pan

Metals are produced from their ores by a process called reduction.

e.g. gold

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The reactivity series of metalsThe reactivity series of metalsDifferent metals have different reactivities. A more reactive metal will remove oxygen from the oxide of a less reactive metal when a mixture of the two is heated.

When a mixture of powdered aluminium and iron(III) oxide is ignited by a high temperature fuse, molten iron is formed. This reaction is called the thermit reaction and is used to weld sections of railway track.

crucible

A mixture of aluminium and iron(III) oxide reacting together

railway trackrailway track

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The reactivity series of metalsThe reactivity series of metalsThis table shows the reactivity series of common metals, and how they are extracted from their ores.

Reactivity Element Extraction method Reaction with acid

Strong K (Potassium)

Electrolysis

Too dangerousNa (Sodium)

Ca (Calcium)

Releases hydrogen and dilute hydrochloric acid.

Mg (Magnesium)

Zn (Zinc)

Chemical reduction

Fe (Iron)

Sn (Tin)

Cu (Copper) Doesn’t release hydrogen and dilute hydrochloric acid. Weak Ag (Silver)

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Extracting iron from its oreExtracting iron from its ore Chemical reduction with carbonChemical reduction with carbon 1. Raw materials (iron ore, coke and

limestone) are added at the top of the furnace.

1000°C

1500°C

2000°CBlasts of hot air

Blasts of hot air

Molten slag

(impurities)

Outlet for molten iron

Outlet for the slag

Load if iron ore, coke and limestone

Gas outlet

Molten iron

The blast furnace

2. Blasts of hot air (which give the furnace its name) are blown in near the bottom of the furnace.

3. Oxygen in the blasts of air reacts with coke (carbon) to form carbon monoxide.

2C + O2 2CO

This reaction is very exothermic and the temperature in the furnace reached 2000°C.

4. As the carbon monoxide rises up the furnace, it reacts with the iron ore (iron(III) oxide to form iron.

Fe2O3 + 3CO 2Fe + 3CO2

5. Molten iron runs to the bottom of the furnace. It is tapped off from time to time.

6. The molten iron is used to make steel or poured into moulds to solidify. The large chunks of iron formed are called ‘pigs’ so this metal is called ‘pig iron’.

Steel – properties and usesIron from the blast furnace is very brittlebrittle because it contains up to 4.5% carbon.

Most of this iron is converted to steel, which is far more useful, by removing most of the carbon. Mild steel Mild steel contains approximately 0.5% carboncontains approximately 0.5% carbon.

Hard steel contains up to 1.5% carbon.

Car bodies Tinplate

It is possible to treat steel .

Heat treatment Creating alloys with other metals

Stainless steel (chromium and nickel)

Very hard steel (tungsten)

Tough steel (manganese)

machines Domestic appliances

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Recycling steel

Steel is recycled on a large scale.

Saves up to 50% Saves up to 50% of energy costsof energy costs

Helps to conserve Helps to conserve iron oreiron ore

Cuts down the emission Cuts down the emission of greenhouse gasesof greenhouse gases

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Electrolysis – backgroundElectrolysis – background

Electrolysis is a chemical reaction. Current enters the electrolyte via two solid conductors called electrodes.

Conducting liquid –

electrolyte

Electrodes

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The anodeanode is the positive electrode, and the cathodecathode is the negative electrode.

Negative Electrode

Positive

electrode

Electrolyte

ion+ion- ion+ion

-ion+ion

-

ion+ion-

The positive ions (cationsions) move towards the negative electrode, and the negative ions (anions)anions) move towards the positive electrodes.

Electrolysis – backgroundElectrolysis – backgroundA

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Electrolysis – extraction of reactive metalsElectrolysis – extraction of reactive metals

carbon anodes

aluminium oxide in molten cryolite

crust of solidified electrolyte

Molten aluminium tap hole

insulated cell casing

carbon lining to cell acting as the cathode

Electrolysis of aluminium oxide (alumina)

Bauxite – a rock containing aluminium

Remove impurities by chemical method

Aluminium oxide powder (alumina), with a very high melting point

1. Aluminium oxide is dissolved in molten cryolite (about 950°C).

2. Oxygen gas is formed at the carbon anodes, and at that high temperature the anodes react with oxygen, burning away and having to be replaced from time to time.

3. Aluminium in the form of a molten metal forms at the cathode.

4. The tap hole is used to collect the aluminium, the crust needs to be broken to add more aluminium oxide.

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The equations for the reaction:The equations for the reaction:

Al3+ +3e Al

2O2- -4e O2

Positive aluminium ions are attracted to the negative cathode, where they gain electrons and form aluminium metal.

Negative oxide ions are attracted to the positive anode, where they lose

electrons and form oxygen gas.

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Railway links

Roads

Port

A good transportnetwork

in and out

Nuclear Power StationHydroelectricPower Source

Build aluminium works near cheap sources

of electricity

A lot of electricity is required for producing the metal via

electrolysis

The raw materials and the product need to be transported easily

Locating aluminium worksLocating aluminium worksA

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Properties of aluminiumProperties of aluminium

light

strong

density of 2.7g/cm3

layer of aluminium oxide (this prevents corrosion even though the metal is very

reactive)

Using aluminiumUse Reason

1. High voltage power cables for the

National Grid

Light, resistant to corrosion

2. Saucepans and kitchen foil Good conductor of heat, non toxic

3. Window frames and greenhouses Strong and light

4. Drinks cans Strong and non toxic

5. Aeroplane and car bodies Strong and resistant to corrosion

resistant to corrosion

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Properties of copperProperties of copper

excellent conductor of electricity and heat

malleable

ductile

non toxic

Use of copperUse Reason

1. Wires in electrical circuits Good conductor of heat

2. Saucepans Good conductor of heat and non toxic

3. Jewellery Malleable and ductile, attractive colour and lustre

4. Water pipes Non toxic and malleable

5. Produces the alloy bronze (copper + tin) and brass (copper + zinc)A

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Properties of titaniumProperties of titaniumgood conductor of heat and electricity

light

tough

non toxic

Using titaniumUse Reason

1. Aircraft industry Light, tough, non corrosive

2. Surgical equipment Light, tough, non corrosive

3. Artificial joints, plates for bone fractures

Non toxic, light, tough, non corrosive

4. Jewellery Non toxic

5. Titanium dioxide is the basis of white paint.

non corrosive

strong

high melting point

low density

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Fluctuations in the cost of metals can affect the economy.

The consequences of metal extractionThe consequences of metal extraction

When the ore runs out, the mine workings may be abandoned causing a deterioration of the landscape.

Important for the economy (Economic boom in the UK during Industrial Revolution).

Extraction and processing of minerals creates employment.

Importing metals is very expensive for the country.

Processing minerals have a detrimental effect on the environment.

A lot of electricity is needed to produce aluminium.

Many minerals are sulphides – produce sulphur dioxide (the gas that causes acid rain).

Sometimes less useful and toxic metals are found with the ones that are needed.

Advantages Disadvantages

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