C1.3- Metals and their uses

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Where are metals generally found?
In the Earth’s crust
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Why do metals have to be chemically separated before they can be used?
They are chemically combined with other elements, e.g. oxygen.
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What is an ore?
When a metal is combined with other elements to form compounds
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Give the stages which copper ore has to go through to be extracted from rock.
Mined from the ground Ground into fine powder Mixed with water and a chemical that makes copper compound repel water Air bubbled through mixture Copper compound floats to top as froth
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What two things determine whether it is worth extracting a particular metal?
1. How easy it is to extract from its ore 2. How much metal the ore contains
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Why are gold and silver found as elements instead of metal ores?
They are very unreactive.
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What is the reactivity series?
A list which puts the metals in order of their reactivity
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Which is more reactive, calcium or zinc?
Calcium
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True or false – Calcium would replace zinc from its compound.
True
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Which metals can be extracted using carbon? Why?
Copper, lead, iron, tin and zinc. Because they are lower than carbon in the reactivity series.
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What has to be done to cause carbon to replace a metal oxide?
The carbon and metal oxide must be heated together.
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Give the word equation for the extraction of zinc from zinc oxide using carbon.
Zinc oxide + carbon = zinc + carbon dioxide
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What type of reaction is the removal of oxygen from a compound?
Chemical reduction
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How are metals more reactive than carbon extracted from their ores?
Electrolysis
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What does iron ore contain?
Iron oxide (iron combined with oxygen)
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What element is used to extract iron from its ore?
Carbon
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What is iron extracted from its ore in?
A blast furnace
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Write the symbol equation for the overall reaction in a blast furnace.
2Fe2O3 + 3C= 4Fe + 3CO2
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What type of reaction is this?
Reduction reaction
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How pure is the iron straight out of a blast furnace?
96%
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What is the main impurity?
Carbon
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What effect do the impurities have on the iron?
They make it brittle, very hard and not easily compressed.
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What is cast iron?
Iron which has been poured in moulds when molten and allowed to cool
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What are the properties of pure iron?
Soft and easily shaped
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Why is pure iron not very useful?
It is too soft for most uses.
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How can the properties of iron be improved?
By adding tiny amounts of other elements
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What is an alloy?
A metal that is mixed with other elements
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What is steel?
What is steel?
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What percentage of carbon is in carbon steel?
0.03–1.5%
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Why is this type of steel so popular?
It is cheap, malleable and not brittle.
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Complete the sentences:
Low-carbon steel is soft and easily shaped. Low-carbon steel is less likely to shatter on impact with a hard object. High-carbon steel is very strong but brittle.
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Why is mild steel very useful in mass production of car bodies?
It is very easily pressed into shape.
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Why are low-alloy steels more expensive than carbon steels?
Because they contain between 1% and 5% of other more expensive metals
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What is nickel-steel alloy used for?
Long-span bridge Bicycle chains Military armour-plating
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What metals are added to iron in stainless steel?
Chromium and nickel
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What are the properties of stainless steel?
Hard, strong and corrosion resistant
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Why are some metals not always appropriate for uses such as aeroplanes?
They are dense and therefore very heavy.
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Which two metals are both strong and have a low density?
Aluminium and titanium
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What other property makes these metals very useful?
They are corrosion resistant.
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What makes aluminium an ideal metal for electricity cables?
It is an excellent electrical conductor and can be drawn in to wires easily.
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How is aluminium non-corrosive despite being fairly high in the reactivity series?
The aluminium atoms on the surface react with oxygen to form a layer of aluminium oxide which stops any further reaction taking place.
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Why are other elements often added to aluminium?
To form alloys to make aluminium stronger
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Why can we not use carbon to extract aluminium?
Aluminium is higher in the reactivity series than carbon.
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How is aluminium extracted?
Using electrolysis
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Briefly describe this process.
An electric current is passed through molten aluminium oxide to break it down.
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Give the stages of producing aluminium from its ore.
- Mining - Separate from impurities - Oxide melted - Electrolysis
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What properties make titanium a very useful metal?
It is very strong, has low density and is resistant to corrosion.
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What effect does the oxide layer on the outer surface of titanium have?
It becomes corrosion resistant.
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What is the melting point of titanium?
About 1660 degrees C
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Give the reasons why titanium is ideal for the following uses.
Bodies of high-performance aircraft – Strong and low density. Parts of jet engines – Maintains strength even at high temperatures Parts of nuclear reactors - Can withstand high temperatures and is corrosion resistant. Replacement hip joint – Light
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Why is carbon not used to extract titanium from its oxide?
It produces titanium which is very brittle.
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How is titanium extracted?
By using a more reactive metal such as sodium or magnesium
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Why is this a problem?
The more reactive metal has to be first extracted by electrolysis.
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What must happen before titanium can be displaced from its ore?
The titanium oxide must be separated and converted to titanium chloride.
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How is the chloride purified?
By distillation
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Why is the extraction of titanium so expensive?
It has many steps which each take time and cost money.
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Where is most copper extracted from?
Copper-rich ores
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What two methods are used to remove copper from the ore?
1. Using sulfuric acid to produce copper sulfate before extracting the copper 2. Smelting (roasting)
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Give an ore in which copper can be found.
Chalcocite
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In what form is the copper in this ore?
Copper (I) sulfide
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Give the symbol equation for the decomposition of copper sulfide in air.
Cu2S + O2 = 2Cu + SO2
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What is the problem with this method of copper extraction?
Sulfur dioxide gas is produced as a waste product which causes acid rain.
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How is this problem overcome?
Chimneys are fitted with basic ‘scrubbers’ to neutralise the acidic gas.
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Why is purifying copper expensive?
It uses a lot of heat and electricity.
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What charge are copper ions?
Positive
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Which electrode are copper ions attracted to?
The negative electrode
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How is very pure copper extracted?
By using many cells running at once
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Why can iron be used to extract copper from copper sulfate?
It is more reactive than copper
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Why do scientists need to find new ways of extracting copper?
Copper-rich ores are limited and running out.
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Give an example of a new method of extracting copper.
Bioleaching OR phytomining
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What are the stages of phytomining?
Plants grown on ground containing low-grade copper ore, Plants are burnt, Copper extracted from ash
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How is the copper extracted from the ash in phytomining?
By adding sulfuric acid which forms copper sulfate which can then undergo electrolysis
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What is a leachate?
A solution of copper ions produced by bacteria feeding on low-grade metal ores
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What percentage of copper comes from bioleaching?
About 20%
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What are the general properties of the transition metals?
Good conductors of electricity and energy, Strong, Can be bent or hammered into shapes (malleable)
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Why is copper an ideal metal for use in water tanks or pipes?
It can be bent but is hard and does not react with water.
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Why are the transition metals so useful?
They can be used in very different ways as between them they have a wide variety of properties.
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What was the first alloy made by humans?
Bronze
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What elements are combined to form this alloy?
Tin and copper
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What alloy is made by the combination of copper and zinc?
What alloy is made by the combination of copper and zinc?
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Why is this alloy ideal for musical instruments?
It is hard but can be worked into intricate shapes.
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How many alloys of aluminium are there?
Over 300
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What is commonly combined with gold to produce alloys used for jewellery?
What is commonly combined with gold to produce alloys used for jewellery?
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What can we alter by adding more or less copper to gold?
the shade
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What is the percentage purity of 12 carat gold?
50%
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Give five environmental issues associated with exploiting metal ores.
1. Huge pits scar the landscape 2. Noise pollution 3. Large amounts of waste rock 4. Groundwater can become acidic 5. Escaped gases can cause acid rain (also accept collecting dust clouds)
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Which metals can be extracted by phytomining?
Copper/nickel/thallium/gold
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How much aluminium does the average person use each year?
8 kg
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Why is recycling aluminium more desirable than extracting it from its ore?
It saves about 95% more energy as electrolysis is not involved.
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How are tin cans separated from general waste?
Using a magnet
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Why does recycling have a positive impact on air pollution?
Recycling metals saves lots of energy that is often supplied by burning fossil fuels.
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What is the most commonly used metal?
Steel
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Why is stainless steel not used for large-scale building?
It is too expensive.
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What effect can rusting have on steel?
It will affect its strength
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Other cards in this set

Card 2

Front

Why do metals have to be chemically separated before they can be used?

Back

They are chemically combined with other elements, e.g. oxygen.

Card 3

Front

What is an ore?

Back

Preview of the front of card 3

Card 4

Front

Give the stages which copper ore has to go through to be extracted from rock.

Back

Preview of the front of card 4

Card 5

Front

What two things determine whether it is worth extracting a particular metal?

Back

Preview of the front of card 5
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