C15

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What is corrosion caused by?
Chemical reactions between the metal and substances in the environment
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What can the products of corrosion affect?
Strength + appearance
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What is the problem with rust?
Forms on surface of iron, crumbly and flakes off so more iron can rust
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What is the chemical equation for the rusting of iron?
*
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What is needed for iron to rust?
Air + water
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How can we prevent iron from rusting?
Coating iron with paint, oil, grease, plastic, less reactive metal or a more reactive metal
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What does it mean if iron is galvanised by zinc?
Protected by it, covered in it
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Why is iron galvanised by zinc?
Zinc is more reactive so if scratched iron does not rust
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What is sacrificial protection?
Protection against rusting even when iron is exposed to air + water, iron must be attached to more reactive metal
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Why are alloys harder than pure metals?
Regular layers in a pure metal are distorted by differently sized atoms in an alloy
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What is bronze made out of?
Copper+tin
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What is a use of bronze?
Statues, ships propellers
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What is brass made out of?
Copper + zinc
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What is a use of brass?
Door fittings, taps, musical instrument
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Why can aluminium be alloyed with a wide range of other elements?
Low density
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What is gold alloyed with to make jewellery?
Copper
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What is the purity of gold measured in?
Carats
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What are steels?
Alloys of iron with carbon or other elements
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How can you change the properties of steel?
Changing the amount of the element alloyed
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How are carbon steels made?
Removing most carbon from iron obtained from a blast furnace
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What are carbon steels used for?
Bodies of cars, ships, containers
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What are the properties of high carbon steel?
Strong+brittle
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What are the properties of low carbon steel?
Soft, easily shaped, less likely to shatter
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What are nickel-steel alloys used to make?
Long-span bridges, bicycle chain and military armour plating
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Why is nickel-steel used here?
They are very resistant to stretching forces
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Tungsten steel operates under what conditions and a usage?
Hot ones, e.g. drill bits
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The chromium-nickel steels are known as what?
'Stainless steels'
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What do they do?
Combine the hardness + strength w great resistance to corrosion, DO NOT RUST
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What is a use of stainless steels?
Cooking utensils+cutlery
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Where are stainless steels used in the chemical industry?
Reaction vessels, makes chemical plants expensive to set up
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What do the properties of a polymer depend upon?
Monomers used + conditions chosen to carry out reaction
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How to make LD (low density) poly(ethene)?
High pressures+trace of O2
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What are the polymer chains like in a LD poly(ethene)
Randomly branched + cannot pack close together
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How to make HD(high density) poly(ethene)?
Catalyst, 50 degrees, raised pressure.
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What are the polymer chains like in a HD poly(ethene)
Straighter, pack closely, high softening temp
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What are thermosoftening polymers?
Will soften or melt easily when heated because their intermolecular forces are weak
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What are thermosoftening polymers made up of?
Random chains tangles together
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What are thermosetting polymers?
Don't melt when heating, strong covalent bonds
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How does a thermosoftening polymer remould?
When it cools down, intermolecular forces bring polymer molecules back together so hardens
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Why won't thermosetting polymers not soften?
Because of their cross linking chains but will char at high temp
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What do the cross linking chains do?
The covalent bonds between chain will not allow chains to separate
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What is soda-lime glass made up of?
Sand, limestone + sodium carbonate
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How is soda-lime glass made?
Raw mats heated to 1500 degrees, they melt, react to form molten glass, cools and goes to solid
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What does the structure of glass look like?
Disorderly, they are frozen in place*
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How can other types of glass be made?
Incorporating other mats into glass
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What are the properties of clay ceramics?
Hard, brittle,electrical insulators, resistant to chemical attack
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How are clay ceramics made?
Wet clay into desired shapes, heating in furnace to around 1000 degrees
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What are some examples of ceramics?
Bricks, tiles, crockery, baths, sinks
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What does the clay contain?
Compounds of metals + non metals
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How are the ions and atoms arranged?
In giant structures that form layers
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What makes the clay slimy when wet?
The fact that the water molecules can go through the layers
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What happens in a furnace to the water molecules?
The water is driven out, strong bonds formed between layers,
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What is the rule between temp and hardness?
The higher the temp, the harder the ceramic
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Why are ceramics brittle?
A sharp blow can distort layers on structure so ions repel each other away which creates cracks
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What are composites?
Two materials, one as a binder for other, improving a desirable property that neither they could offer alone
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What is reinforcement?
one material surrounding and binding together fragments of the other material
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Composites of ceramics with polymers have what properties?
Tough, flexible (fibreglass),
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What is fibreglass made out of?
Fine threads of glass embedded in a polymer resin that harden once moulded
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What are the properties of fibreglass?
Tough, flexible + waterproof
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What are some more examples of composites?
Wood, (plywood) which is thin sheets of wood glued together, concrete
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What is concrete made of?
Cement, sand, gravel and water
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Why do plants need nitrogen?
To make proteins
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Why do farmers disturb nitrogen recycling?
Harvest them so no nitrogen goes in soil when they rot
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Why cant plants absorb nitrogen from the air?
The gas is insoluble in water and most plants need a soluble nitrogen form
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What are the raw mats for ammonia?
Nitrogen + hydrogen from natural gas which also contains methane
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How does the haber process work?
Nitrogen + hydrogen purified, passed over iron catalyst at 450 degree temp and 200 atmospheres
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What does it mean by the reaction is reversible?
Ammonia gas breaks down back into nitrogen + hydrogen
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How is the ammonia removed?
Cooling the gases so ammonia liquifies
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What happens to the unreacted nitrogen + hydrogen?
Recycled back + compressed + heated
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What is the chemical equation for this?
*
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What is the cost of extracting nitrogen from air?
Nothing but u must separate from the other gases using fractional distillation
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How is hydrogen made for the process?
Methane + steam = hydrogen + carbon monoxide
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What is the problem with this?
Heating water to make steam + buying methane gas
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Because they is 4 molecules of gas on left side of reaction and two on right side what happens if there is an increase in pressure?
Shift position of equilibrium to the right to produce more ammonia to reduce the pressure
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How to get max yield of ammonia?
High pressure
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Problem with this?
Lots of energy needed for compression,expensive vessels + pipes
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Why is there a compromise of 200 atmospheres?
Lower yield but reduces cost-and helps a reasonable rate of reaction
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What type of reaction is the forward reaction?
Exothermic
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What would happen if we lowered the temp?
Increase yield of ammonia, because fwrd reaction transfers energy to surroundings so temp raises
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What happens to the rate of reaction at low temp?
Slow, gas molecules collide less freq
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Why is compromise of 500 degrees?
Low temp affects catalyst, high temp for reasonable ROR
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Why is the iron catalyst used?
Speed up ROR, by same amount f+b
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What can ammonia be made into?
Nitric acid
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How to make the ammonium nitrate fertiliser?
*
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How to make ammonium phosphate?
*
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How to make ammonium sulphate?
*
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Apart from nitrogen what else do plants need?
Potassium+ phosphorus
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What do bags of NPK fertilisers contain?
Formulations of all macro-nutrients
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What are the sources of phosporus used?
Phosphate rock, dug from ground, insoluble in water so must be treated with acids
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How is phosphoric aid + calcium nitrate made?
By treating the rock with nitric acid
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What can the phosphoric acid be neutralised with to produce ammonium phosphate?
Ammonia
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How is the single superphosphate ( calcium phosphate + calcium sulfate) made?
Treating rock with sulfuric acid
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How is the triple superphosphate (calcium phosphate) made?
Treating rock with phosphoric accid
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Where are the potassium salts mined from?
Ground, soluble in water
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Other cards in this set

Card 2

Front

What can the products of corrosion affect?

Back

Strength + appearance

Card 3

Front

What is the problem with rust?

Back

Preview of the front of card 3

Card 4

Front

What is the chemical equation for the rusting of iron?

Back

Preview of the front of card 4

Card 5

Front

What is needed for iron to rust?

Back

Preview of the front of card 5
View more cards

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