Metals that make up less than 0.1% of the Earth’s crust are considered to be scarce. Silver (abundance 0.000 01%) and gold (0.000 000 5%) are scarce and therefore expensive, but some of our most commonly used metals are considered scarce too: copper (0.007%), mercury (0.000 05%), zinc (0.013%), lead (0.0016%) and tin (0.004%).
Eating gold
In many cultures, it has been traditional to decorate food with
pieces of gold leaf (fine layers of hammered gold). Many of Australia’s top restaurants are
now using it too, on top of dishes such as risotto and even
in cocktails. The gold leaf is eaten but has no taste, smell or
texture. Injections of gold have been used for many years as relief from arthritis, so maybe this will help justify the cost of
eating it!
Fig 2.2.10 More than 50% of all aluminium cans in
Australia are collected and reprocessed.
Metal Element Amount used Estimated year
symbol per year at which known
(millions of reserves of the
tonnes) metal will run out
Iron Fe 800 2110 Aluminium Al 12 2350 Copper Cu 8 2040 Zinc Zn 4.5 2060 Lead Pb 4 2020 Tin Sn 0.25 2015
Worksheet 2.3 Extraction of metals
Recycling of aluminium is common, because the production cost of new aluminium is twenty times more than the cost of recycling it. Recycling of many metals is often too expensive to make it worthwhile. The difficulty of separating the iron from tin in food cans makes it far too expensive to recycle iron at the moment, despite millions of cans being thrown out every year.
Mining and metals
UNIT
UNIT
2.2
2.2
2.2
UNIT
[
Questions
]
Checkpoint
Metals ready to go: native elements
1 Clarify what is meant by a ‘native element’. 2 List four examples of native elements.
3 State two forms in which native elements may be found.
Metals that need work: minerals and ores
4 Modify the following statements to make them correct. a Metals that are not native elements are found as
alloys.
b Rocks containing large amounts of ores are known as
minerals.
c A mineral contains sufficient metal to mine.
5 Use the table on page 30 to list three ores and the main
metal they contain.
Is it worth mining?
6 A mining company decides not to mine a particular
metal. State three factors that might have led to this decision.
7 State two features of a commercially successful mine.
The mining process
8 List the problems of an underground mine. 9 Construct a diagram showing the structure of an
underground mine.
Concentration of the ore
10 From the following list of words, identify the correct
terms to fill in the spaces below.
extraction, froth flotation, ball mill, gangue, crushed Mined material is _________ by rollers or steel balls within a _________. Impurities known as _________ are separated by __________. The remaining ore is now ready for _________.
The activity series
11 Define the term ‘activity series’.
12 State the reason why some metals are more reactive
than others.
13 Metals are extracted from their ores depending on
their position in the activity series. List the extraction methods needed, in order from the least to the most active metals.
Extraction by electrolysis
14 List three metals that can only be extracted by
electrolysis.
15 Use a diagram to explain how sodium is extracted from
sodium chloride by electrolysis.
16 State a disadvantage of using electrolysis for
extraction of metals.
Extraction by heat
17 List three metals that can be extracted by heat. 18 Construct a diagram of a blast furnace and label the
important parts.
19 State the chemical formula for slag.
20 Construct the chemical equations for the smelting of
iron ore.
Recycling versus mining
21 State whether the following statements are true or
false.
a Metals are known as renewable resources. b Iron is the most common metal in the Earth’s crust. c Metals that make up less than 0.1% of the Earth’s
crust are scarce.
22 State one disadvantage and one advantage of
recycling metals.
Think
23 Explain why a reactive metal atom like sodium (Na)
has a very stable metal ion, Na+.
24 State which metal(s):
a are extracted by electrolysis b are extracted in a blast furnace c are extracted by roasting in air d are native
25 Contrast the following: a slag and gangue b mineral and ore c overburden and ore d electrolysis and smelting e stable and reactive
26 Explain why metals higher up the activity series
are more likely to be found as ores than as native elements.
27 Platinum is a native element. Explain where it should
appear in the activity series.
28 Mining companies regularly take out mining leases
on any land that may contain valuable mineral ores. This may even include the land on which you live. If the mining company holds the lease, it has the legal right to buy the land. Do you consider this acceptable?
Justify your answer.
29 Contrast a shaft, a drive and a stope.
>>>
over- burden Al Fe Cu Au extraction Fig 2.2.11[
Extension]
Investigate
1 Research how car bodies can be recycled for their
metals. Construct a poster aimed at convincing the public that recycling car bodies is a useful idea.
2 Research how to pan for gold and design an
instruction sheet.
3 Locate a current mining town in Australia. a Describe the ore mined there.
b Use a map to summarise where it is processed
and extracted.
c Describe the transport facilities that probably
had to be built to mine and shift the ore, giving consideration to whether it is near a large town.
4 Underground miners used to carry canaries
with them. Research why and use a cartoon to
summarise your research.
5 The mobile phone revolution has brought with it a
problem of recycling unwanted phones and batteries.
Research what metals are used in making mobile
phone batteries and the difficulties they produce if not recycled responsibly. Construct a brochure that could be used to inform the public.
Action
6 a Record the number of cans and types of cans
your household throws out in a week.
b Estimate how many cans are thrown out per year. 7 a Construct a bar chart of current prices of metals
listed in the commodity prices of the newspapers.
32 Use the activity series to predict whether these metal
ions and metal atoms would swap electrons:
a Na and Au+ b Na+ and Au c Mg and Cu2+ d Pb2+ and Al e Ca2+ and Cu
Skills
33 Construct a bar graph showing the elemental
composition of the Earth’s crust.
34 The years for the
first successful extraction of different metals are shown in the table.
a Construct a time line showing these discoveries. b Use the activity series to explain why different
metals were discovered at different times in history.
Analyse
30 List three sites where each of the major ores listed in
the table on page 30 are mined.
31 Use the words below to complete the flow chart in
Figure 2.2.11 summarising the process of mining an ore and extracting the metal it contains.
exploration, electrolysis, gangue, froth flotation, crushing, native-metal, roasting slag, blast furnace, open-cut, underground
Mining and metals
Mining and metals
Aluminium 1890 AD
Zinc 1500 AD
Iron 1400 BC
Lead 2000 BC
UNIT
UNIT
[
Practical activity]
2.2
UNIT
Prac 1 Unit 2.2Electrolysis of copper
Aim To extract solid copper from a solution
Equipment
1 M sulfuric acid, black copper oxide, spatula, 50 mL beaker, glass stirring rod, Bunsen burner, tripod, gauze mat, bench mat and matches, 12 V power pack, globe, electrodes and connecting leads, filter paper/paper towel
Method
1 Pour approximately 20 mL of 1M sulfuric acid into the
beaker.
Fig 2.2.12
2 Add a small spatula of black copper oxide.
3 Carefully warm over a yellow Bunsen burner flame. Stir
with the glass rod until all the copper oxide is dissolved and the solution is blue. Do not boil.
4 Remove the beaker from the tripod and place on the
bench mat.
5 Connect up the circuit as shown in Figure 2.2.12. Set
the power pack on 6 V DC and allow it to run for a couple of minutes.
6 Draw a diagram of the set-up. Mark the electrode being
copper plated. What is happening at the other electrode and to the colour of the solution?
7 Turn off the power and remove the electrodes. Carefully
remove any pure copper onto filter paper/paper towel.
Questions
1 Explain whether copper formed at the positive or
negative electrode.
2 Explain what happened to the blue colour of the
solution.
3 In this experiment, copper ions in the solution are taking
back electrons to form copper atoms. Describe the evidence for this.
4 Construct a balanced chemical equation for what is
happening to the copper ions.
5 Propose a reason why electrolysis is never used
commercially to produce copper.
6 Aluminium can only be extracted by electrolysis. Propose a reason why copper and not aluminium was
used in this experiment.