GCSE Chemistry C15 - Using Our Resources

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What is rusting?
The corrosion of iron.
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What is rust?
Rust forms on the surface of iron and most steels. It is a soft, crumbley substance and can flake off, exposig more of the iron to rusting.
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How is aluminium protected from rusting?
A protective oxide layer foms over aluminium metal which protects the aluminium underneath it from corroding.
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How can rust be prevented?
By coating the iron (or steel) with paint, oil or grease, plastic or a less/more reactive metal.
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What is sacrificial protection?
For example, when zinc is used to coat iron and is a stronger reacting agent than iron and becomes oxidised. Therefore any water or oxygen reacts with the znc instead of the iron and so the zinc is sacrificed to protect the iron.
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What can be used as sacrificial protection for iron?
magnesium, aluminium or zinc because they are all more reactive tan iron.
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What is an alloy?
a mxture of metals made up of different sized metal ions which make it harder for the layers to slip over one another. This makes alloys very hard.
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What is a bronze alloy?
Made by mixing copper with tin and used to make statues and decorative items.
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What is a brass alloy?
Made by alloying copper and zinc can be hammered into sheets and pressed into intricate shapes, used to make musical instruments and taps.
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What are aluminium alloys?
Aluminium can be alloyed with a wide range of elements which have different propertes. Some are lightwight but strong and are used to build aircraft.
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What are gold alloys?
Usually alloyed with coper when making jewellery. Pure gold wears away more easily than its alloy with copper.
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How do you calculate the fraction of gold in your jewellery?
By dividing the carat umber by 24.
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What are steel alloys?
Alloys of iron with carbon and or other elements
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What are carbon steel alloys?
Made by removing most of the carbon from the iron obtained from a blast furnace. These are the chepatesy steels to make and used in containers and the bodies of cars.
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What are the properties of high carbon content and low carbon content steel?
High - very strong and britle. Low - soft and easily shaped, lss likey to shatter.
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What are nickel-steel alloys used for?
making long-span bridges and bike chains as they are very resistant to stretching forces.
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What are tungesten steel alloys used for?
Operates very well under hot conditions so used to make high speed tools like drills.
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What is stainless steel?
It is hard, strong and has great resistance to corrosion - it doesn't rust! Thses are used to make reacion vessels.
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What do the properties of polymers depend on?
The monomers used to make it ad the conditions chosen to carry out the reaction.
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How is low density (LD) polyethene formed?
using very high temperatures and a trace of oxygen. The polymer chains are randomly branched and cannot pack closely together.
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How is high denisty (HD) polyethene formed?
USing a catalyst at 50 degrees and a slightly raised pressure. This chains can pack closely together.
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What are thermosoftening polymers?
Individual polymer chains tangled together, they will soften easily and re-set when they cool down.
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What are thermosetting polymers?
They do not melt when heated and have strong covalent bonds forming links between the polymer chains.
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Describe the forces between thermosoftening polymers:
Weak intermolecular forces that brak when heated when the polmer cools down, the intermolecular forces bring the polymer molecules back together.
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Describe the forces beween thermosetting polymers:
Monomers form covalent bonds when they are first heated to shape them, these are strong and the links don't allow them tp seperate so they will not soften.
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How is glass made?
Raw materals 9sand, limetsone and sodium carbonate) are heated to 1500 degrees and they melt and react to form molten glass. As it cools, the glass turns into a solid but the particles remain as if they are frozen in place.
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What is born trioxide glass used for?
Ovenware and testubes as it melts at a higher tenperature than soda-lime glass.
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What are ceramics used for?
Making bricks, bathroom seats, baths and toilets. They are made by moulding clay into the desired shapes and heating them in a furnace at 1000 degrees.
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Hpw ar ceramics made?
The clay cotains metal and non metal compounds with ionic bonding and some covalent bonding between non metal atoms. They are arranged in layers ad when the clay is wet water molecules get between the layers but when it is burned strong bonds form.
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Give one property of ceramics:
Brittle.
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What are composites?
Made up of two materials and often involve a binder of one material surrounding and binding fibres of another material (reinforcement).
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Why are composites hard ad very tough, not brittle like ceramics?
As the glass melts between the crystals in the ceramic so any cracks cannot spread through the whole structure.
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What is fibreglass?
Made of fine threads of glass and hardens once moulded into shape. It forms a tough, flexible and waterproof material ideal for kayaks.
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Examples of wooden composites:
Plywood, made of thin sheets of wood glued togetehr and MDF, made from woodchips and can be cut into an intricate shape without splitting.
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What is concrete?
Made from cement, sand and gravel, very hard and very strong.
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Why do farmers ned fertilisers to replace nitrgen and other nutrients in the soil?
As nitrogen is absorbed from the soil during growth and is therefroe not all replaced by the natuarl cycle of nitrogen?
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What is the haber process?
A way of turning nitrogen in the air into ammonia, mainly to make fertilisers.
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What are the raw materials for the haber process?
Nitrogen from the air and hydrogen, mainly from natural gas.
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What happens during the haber process?
Nitrogen and hydrogen purified, passed over an iron catalys at 450 degrees and a high pressure, 200 atmospheres. The product of ths reversible reaction is ammonia.
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How is ammonia removed from the haber process?
By cooling the gases so the ammonia liquifies and then it is seperated from the unreacted nitrogen and hydrogen gases, which are recycled back into the reaction mixture.
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Why is the haber process carried out under specific conditions?
To give a reasonable yield of ammonia as wuickly as possible.
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How does pressure effect the yield of ammonia?
A high pressure, but this means lots of energy is needed to compress the gases so very expensive. As a compromise, 200 atmospheres is used to get a high yield bu keep costs low.
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How does temperature effect the yield of ammonia?
A compromise of a reasonably high temperature to stop the reaction from being very slow even though this does reduce the yield of ammonia.
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How does the catalyst effect the yield of ammonia?
Speeds up the rate of the forwards and backwards reaction by the same amount so has no effect on yield but does cause it to be produced more quickly.
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How can ammonia be neutralised with acids to make other fertilisers?
Neutralised with sulfuric acid to make ammonium sulfate fertilser and phosphoric acid to make ammonium phoshate fertiliser.
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How is ammonium nitrate fertiliser made?
Ammonia is used to make nitric acid and then the nitric acd can be reacted with more ammonia to make ammonium nitrate fertiliser.
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What are fertilisers used for?
To supply nitrogen, phosphorus and potassium to plants. They can be added to land together in mixtures called NPK fertilisers.
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How is phosphorus sourced for NPK fertilisers?
From phosphate rock, which is mined and treated with acids from fertilisers like ammonium phosphate.
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How is potassium sourced for NPK fertilisers?
Comes from potassium salts mined from the ground for use of fertilisers like potassium chloride.
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Other cards in this set

Card 2

Front

What is rust?

Back

Rust forms on the surface of iron and most steels. It is a soft, crumbley substance and can flake off, exposig more of the iron to rusting.

Card 3

Front

How is aluminium protected from rusting?

Back

Preview of the front of card 3

Card 4

Front

How can rust be prevented?

Back

Preview of the front of card 4

Card 5

Front

What is sacrificial protection?

Back

Preview of the front of card 5
View more cards

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