boardworks ltd 2001 ks4: useful materials from metal ores

© Boardworks Ltd 2001

KS4: Useful Materials FromMetal Ores


Getting Metals From Ores

1. First substances other than the metal compound are removed (concentration.)

2. Next the metal itself is extracted from its compound (reduction).

Most metals do not occur naturally (native).They have to be extracted from metal containing rocks (ores.)


Extraction of Metals and Energy Changes

• The more vigorously an element forms compounds the harder it will be to get back that element from its compounds.

• Eg. Magnesium gives out lots of heat when it combines with oxygen.

• This means we will have to put lots of energy back to extract magnesium from magnesium oxide. I.e. It will be hard to extract.


Extraction Processes

The ReactivitySeries

potassiumsodiumcalciummagnesiumaluminium

zinciron

copper

gold

(carbon)

Incr

easi

ng re

activ

ity

Metals above carbon must be extracted using electrolysis.

Metals below carboncan be extracted from the ore by reduction using carbon, coke, or charcoal.

Gold and silver often do not need to be extracted. They occur native.

The reactivity of a metal Determines the methodof extraction.

lead

silver


Extracting Methods• Here is a list of the symbols of some mostly less

common metals in order of decreasing reactivity.• Use this to assign the most likely method of extraction:

native (N), carbon(C), electrolysis (E).• Li, Ce, Mn, Al, Zn, Cd, Sn, Pb, Cu, Pd,

Method(N, C or E)

Symbol SnCd AlCuPdCeMnZnLi

Activity


Extracting Gold

• Because gold occurs native its extraction is a low-tech affair that simply involves finding it!


Iron• Iron is a moderately reactive metal.• Iron ore is plentiful and relatively easily

reduced to iron metal by heating with coal (carbon). It is therefore cheap.

• It is strong and malleable (non-brittle).• Iron is the most commonly used metal.


Extracting Iron – The Blast Furnace


Reactions - Reduction of Iron Ore

carbon + oxygen carbon dioxide

Carbon dioxide + carbon carbon monoxide

Carbon monoxide + iron oxide iron + carbon dioxide

C(s) + O2(g) CO2(g)

CO2(g) + C(s) 2CO(g)

3CO(g) + Fe2O3(s) 2Fe(s) + 3CO2(g)


Reactions – Removing Impurities

Calcium carbonate calcium oxide + carbon dioxide

Calcium oxide + silicon dioxide calcium silicate

CaCO3(s) CaO(s) + CO2(g)

CaO(s) + SiO2(s) CaSiO3(s)

This is called SLAG


Extraction of IronActivity


Copper

• Copper is a metal of low reactivity.• It occasionally occurs native but more

often occurs as copper compounds.• Heating copper compounds with

carbon gives copper but this is not pure enough to use for electrical work.


Electrolytic Purification• The conductivity of copper is

drastically reduced by tiny amounts of impurities.

• Because of this most copper metal is further purified by electrolysis.

• In this process impure anodes dissolve.

• This dissolved copper is plated onto a cathode leaving behind impurities.


Copper Atoms at the Cathode

• Opposite charges attract.• And so positive copper

ions Cu2+ move to the negative cathode.

• At the cathode these ions gain electrons and turn into copper atoms.

• So, in electrolysis a copper cathode gets thicker and thicker


Copper Ions Form at the Anode• Impure copper is used as

the anode of an electrolysis cell.

• The battery pulls electrons off the copper atoms that the anode is made up from.

• By losing electrons these atoms change into copper ions and so the anode slowly “dissolves” away.

• Impurities just sink to the bottom as “anode mud.”


Purification: The Whole Process


Purification: The Half Reactions

Anode (+ve electrode)

Cu(s) Cu2+(aq) + 2e-

Cathode (-ve electrode)

Cu2+(aq) + 2e- Cu(s)


• Copper is purified to improve its NOT CIVIC DUTY

• Copper is purified by CELERY IS LOST

• Pure copper forms at the DO TEACH

• Impurities form called A ODD MENU

• The anode will slowly DIVE LOSS

• At the cathode copper ions gain CORN STEEL

conductivity

electrolysis

cathode

anode mud

dissolve

electrons

Unscramble the words to end the sentences

Activity


Extracting Platinum

• Platinum is a rare and expensive metal used in jewellery and also for plating the fuel nozzles in jet engines. It was first discovered by Europeans in 1735 but in South America the primitive pre-Columbian Indians had been using it for centuries.

Approximately where would you place platinum in the activity series?

In what form do you think platinum occurs?

Activity


Purifying copper and electricity

• Copper is purified using electrolysis. • Plan an experiment to investigate factors

that might affect the rate of copper production.

• Include:– Any factors that might affect rate.– The apparatus you would need.– A statement of how you would control variable in

an investigation.– The number and range of readings.– The safety issues you would take into account.

Activity


Apparatus

Purifying copper: some answers (1)

Some factors that might affect rate.– Concentration of solution.– Distance apart of electrodes– Electrical potential (volts) or current (amps).– Duration of electrolysis.

A

3.3g


Purifying copper: some answers (2)

Control of variables.–Basically only change one variable at a time!

Number and range of readings–Minimum of 8-10 different values–Repeat readings at least once –Attempt a range providing 10-fold change.

Safety Issues–Check electrical, toxicity, corrosive etc.–Take appropriate measures


Aluminium: Properties• Aluminium is a reactive metal.• We might expect it to corrode easily but a

strong coating of oxide on it’s surface prevents this in most everyday situations.

• It has a low density which leads to its extensive use in the aerospace industry.

Al Al Al AlAl AlAl Al Al AlAl Al

O O O O O OO OOCoating of

oxygen atoms prevents further

attack


Aluminium: Ores• It occurs as bauxite ore which is a form of

aluminium oxide.

• Because aluminium is so reactive carbon is unable to pull away the oxygen from it.

• It is extracted by electrolysis of moltenmolten bauxite. Early attempts at this failed because bauxite is so hard to melt.

• If cryolite is added the bauxite melts more easily. This is an essential step in the extraction process.


A bauxite / cryolite mixture is melted in a steel container containing a carbon lining.

Graphite (carbon) anodes

Tanklinedwith

carboncathode

Molten electrolytebauxite + cryolite

Steelcase

Graphite anodes are inserted into the molten electrolyte ready for electrolysis.

Electrolytic extraction


Aluminium Formation• Opposite charges attract.• And so positive aluminium

ions move towards the negative cathode.

• At the cathode these ions gain electrons and turn into aluminium atoms.


Oxygen formation

• Negatively charged oxide ions move to the anode.

• Here they lose 2 electrons and so turn into neutral oxygen atoms.

• These atoms rapidly join into pairs to form normal oxygen gas.


Carbon Dioxide Formation

• Remember the electrolysis is carried out at high temperature.

• Under these conditions quite a lot of the oxygen reacts with the carbon anode.

• Carbon dioxide is formed and the anode is rapidly eaten away and frequently has to be replaced.


Extraction of aluminium: overall

siphonGraphite / carbon anodes

Molten aluminiumMolten electrolytebauxite + cryolite

Tanklinedwith

carboncathode

Moltenaluminiumout

Steelcase

Vented cover


Extraction of aluminium using electrolysis - half reactions

Anode (+ electrode)2O2-(l) O2(g) + 4e-

Cathode (- electrode)Al3+(l) + 3e- Al(l)

Overall2Al2O3(l) 4Al(l) + 3O2(g)

The anode reacts to form carbon dioxide

C + O2 CO2


• Common aluminium ore I axe tub

• Added to reduce melting pointCity role

• The electrodes are made out ofRight ape

• Extracting aluminium is a Cretin duo

bauxite

cryolite

graphite

reduction

Unscramble the words to end the sentences

Activity


Aluminium – the Overall ProcessActivity


A Rotten Week in the State of A Rotten Week in the State of ChemarkChemarkSince the war of 2042 world trade had been drastically reduced.Many countries have a policy of using home produced materials wherever possible because imported materials remain difficult to buy.

The country of Chemark had done relatively well at using its own resources but supplies, even of home produced materials, can be unreliable.


ChemsvilleChemsville

•The major town of Chemsville, in the state of Chemark, has 2 main industries:

-ChemCars – manufacturing expensive cars-ChemComm – engaged in communications products such as newspapers, books, CDs and DVDs

•It also had an 80% completed aircraft factory: ChemJet-ChemJet has orders for 22 executive jets which they are committed to delivering to a tight schedule.

•There are also several large farms within the borders of Chemsville producing crops and meat.


ChemsvilleChemsville


Monday – Fire at ElectroSalt 1• The week starts badly! The company that electrolyses

salt in Chemark has had a major fire. The ElectroSalt factory will not open again for at least 3 months.

• The mayor of Chemsville phones. She urgently wants you to produce a brief report setting out:– What rock salt is used for?– How the factory close-down may affect companies,

farmers and non-industrial activities in Chemsville

Draw up this report for the mayor.

Include diagrams / flow charts of products from salt and suggest problems that the absence of these may cause for Chemsville companies.


Monday: Useful products from RocksaltSome answers for the mayor!

Salt

p.v.c.

Water treatment

Paper bleaching

pesticides

Sodium hydroxide

hydrogen

chlorine Manufacture of Aluminium

Manufacture of paper

Manufacture of textiles


Monday: Answers about Rocksalt

ChemCar & ChemJetPlastic shortages due to lack of chlorine. (Needed for wire insulation and plastic components.)

Textiles shortages (for seat covers etc) due to lack of sodium hydroxide.

Aluminium shortage due to shortage of sodium hydroxide. Major problem for ChemCar and dire problem for ChemJet


Monday: Answers about Rocksalt

ChemComPaper shortages due to lack of chlorine and sodium hydroxide

Plastic shortage needed to make CDs and DVDs


Monday: Useful products from Rocksalt

FarmersShortage of insecticide.

Others

Lack of chlorine for water treatment – health risks if untreated water


Wednesday: Price Rises by ElectroGen

• ElectroSalt had been one of the major customers of the only Electricity company.

• Loss of ElectroSalt’s custom has taken ElectroGen into financial problems and they announce an emergency price rise of 50% for electricity.

• The mayor phones. What effect will this have upon the cost of products made in Chemsville?

Draw up a report for the mayor.

What materials used in existing factories and in the new aircraft factory may involve major quantities of electricity? Can it’s use be avoided?


Wednesday: Report about ElectroGen

• Obviously there are normal running costs in all of the organisations but two vital products will be hit by the price rise and are difficult to get replace.

Copper – for wiring of cars and aircraft. (Copper is refined by electrolysis which uses large amounts of electrical power.)

Aluminium – for use in cars and especially in aircraft. (Aluminium is extracted by electrolysis of molten bauxite.)


Friday: Limestone shortage

• It seemed things could only get better - wrong! • The director of the unfinished aircraft factory phones saying the company providing cement has been unable to get supplies because of a strike at the limestone quarry.

• The aircraft factory mustmust be finished on time.– The director suggests using an old limestone wall and clay from

the foundations of the new factory to make enough cement to finish the factory off. Is this feasible / sensible?

Make recommendations on how to get the cement.

Who else in Chemsville may be affected by a limestone shortage?


• The limestone wall could be heated to produce calcium oxide and this could be mixed with clay to make cement so this could solve the problem.

• It might make more sense to ship the limestone to the existing cement factory to make a batch of cement as they already have the necessary equipment. This is my recommendation.

Friday: Answers to Limestone shortage

Clay

Limestone

Cement


The building of the ChemJet factory is not the only thing that will be affected by a limestone shortage.

The strike will affect manufacture of iron from which steel is made. This could have major effects on ChemCar as many car components are made of steel.

In the longer term it will also affect farmers who use limestone to neutralise their soil.

Friday: Answers to Limestone shortage


1. Which of the following metals is most likely to occur native?

A. SodiumB. ZincC. IronD. Gold


2. Which of the following metals has to be extracted by electrolysis?

A. SodiumB. ZincC. IronD. Gold


3. Which of these happens in the purification of copper?

A. Copper cathode dissolvesB. Copper anode gets thickerC. Copper atoms become ions at the

cathodeD. Copper ions become atoms by gaining

electrons.


4. Which of these happens in the extraction of iron?

A. Carbon oxidises the iron oxideB. Combustion of carbon provides the energy

for the extraction process.C. Carbon monoxide reacts with acidic

impurities in the iron ore.D. The waste gas is mainly carbon monoxide

boardworks ltd 2001 ks4: useful materials from metal ores

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