Topic 15 - Using Resources Flashcards
What is the corrosion of iron called?
Rusting
What is rust?
It is a layer of hydrated iron (III) oxide that forms in the presence of water and oxygen.
How do we prevent rust?
Coating the iron or steel with:
paint
oil or grease
plastic
a less reactive metal
a more reactive metal
What is the process of using Zinc to protect Iron?
Galvanisation
How does sacrificial protection of iron work?
The zinc is more reactive than iron so it has a stronger tendency to form positive ions, as the zinc atoms lose electrons they become oxidised. Therefore, any water or oxygen reacts with zinc rather than iron.
Apart from zinc, what other metals can be used to sacrificially protect iron?
Magnesium and aluminium
What are alloys?
Mixtures of metals that have differently shaped and sized metal ions.
Why do alloys have higher melting points than pure metals?
Due to the differently shaped and sized atoms, layers slip less easily as the layers are distorted.
What was the first alloy made by humans?
Bronze, about 5500 years ago.
What is bronze used for?
Statues + decorative items and ship propellers due to its toughness and resistance to corrosion.
How is bronze made?
Mixing copper with tin.
How is brass made?
By alloying copper with zinc.
What are the properties of brass?
It is harder than copper but more malleable.
What are the uses of copper?
It can be used to make musical instruments and door fittings and taps.
What are aluminium alloys used for?
Building aircraft or armour plating.
How is jewellery made?
Alloying gold with copper.
How does gold alloy compare with pure gold?
Pure gold wears away more easily than its alloy with copper.
How is gold purity expressed?
In carats, where 24 carats is 99.9% pure.
What are steels?
Alloys of iron with carbon and/or other elements.
What are carbon steels?
Steels made from removing carbon from the iron obtained in a blast furnace. They are the cheapest to make.
What is high carbon steel?
A steel with a relatively high carbon content that is very strong but brittle.
What is low carbon steel?
A steel that is soft and easily shaped that isn’t as strong but less likely to shatter on impact with a strong object.
What are alloy steels?
Alloys made with steel for a particular use.
What are stainless steels?
Steels that contain a much higher percentage of other metals made from chromium-nickel. They combine hardness and strength with great resistance to corrosion. They don’t rust so are used in cooking utensils and cutlery.
What do properties of polymers depend on?
-The monomers used to make it.
-The conditions chosen to carry out the reaction.
What are the two types of poly(ethene)?
High density and low density poly(ethene).
How is low density poly(ethene) made?
Using very high pressures and some oxygen, ethene forms it. The polymer chains are randomly branched and cannot pack closely together, hence its lower density.
How is low density poly(ethene) formed?
Using a catalyst at 50 degrees Celcius and a slightly raised pressure, ethene forms it. This is made up of straighter poly(ethene) chains.
They can pack more closely together than branched chains, hence its higher density.
It also has higher softening temperature and is stronger than low density.
What are thermosoftening polymers?
Polymers that soften quite easily and then re-set when cooled down. They are made up of individual polymer chains that are tangled up together.
What are thermosetting polymers?
Polymers that do not melt when we heat them. They have strong covalent bonds forming cross-links between polymer chains.
What happens to forces in thermosoftening polymers?
Forces between polymer chains are weak. When you heat the polymer, the weak intermolecular forces are broken. The polymer becomes soft.
When it cools down, the intermolecular forces bring the polymer molecules back together. The polymer hardens again and it can be remoulded.
What happens to forces in thermosetting polymers?
Their monomers make covalent bonds between chains when first heated. They are strong and stop the polymer from softening. The cross links between chains do not allow them to separate. Even if heated strongly it won’t soften, it will eventually char at high enough temperatures.
What is glass made of?
Mainly sand, Silicon dioxide, limestone and soda.
How is glass formed?
Raw materials are heated to 1500 degress celcius. At high temperatures they melt and react to form molten glass. As it cools it becomes solid. The particles seem frozen in place.
What are some examples of ceramics?
Bricks, tiles, crockery, bathroom sinks, baths and toilets.
What are clay ceramics like?
Hard but brittle materials that are electrical insulators and resistant to corrosion.
How are clay ceramics made?
Moulding wet clay into the desired shapes and heating them with a furnace to around 1000 degrees celcius.
What do clay ceramics contain?
Compounds of metal like aluminium and potassium and non-metals like silicon and oxygen, with ionic bonding between ions, but also some covalent bonding. They are arranged in giant structures that form layers.
What are composites?
Made of two materials, making a product with improved properties for a particular use. They are often a matrix of one material surrounding and binding another.
What are composites like?
They are tough and flexible like fibreglass made of fine threads of glass embedded in a polymer resin that hardens once moulded into shape. It forms a tough, flexible and waterproof material with a low density.
What examples of composites are there?
Fibreglass
Wood
Concrete
What is wood made from?
Thin sheets of wood glued together with grain in successive layers running at angles to each other.
What is concrete made of?
Cement, gravel, sand and water left to set.
What is ammonium nitrate used for?
As a fertiliser by farmers to replenish nutrients for crops.
How is ammonia collected?
From nitrogen gas in the Haber process.
What resources are needed for the Haber process?
Nitrogen from the air
Hydrogen from natural gas
What temperature and pressure is used for the haber process?
450 degrees C and 200 atmospheres.
What type of reaction is the Haber process?
A reversible reaction
What happens during the Haber process?
Ammonia gas breaks down into nitrogen and hydrogen and ammonia is formed by them at the same time.
Ammonia is removed by cooling gases so the ammonia liquifies and can be separated.
Unreacted nitrogen and hydrogen gases are recycled back into the reaction mixture. They are then re-compressed and heated before returning to the reaction vessel. There they have a chance to react again.
What is the word equation for the Haber process?
Nitrogen + hydrogen <–> iron catalyst <–> ammonia
What is the symbol equation for the Haber process?
N2 (g) + 3H2 (g) <–> Fe catalyst <–> 2NH3 (g)
What reaction is carried out to get the hydrogen used in the Haber process?
methane + steam –> hydrogen + carbon monoxide
What is the effect of increases pressure on the Haber process?
Due to Le Chatelier’s Principle, since ammonia has only 2 moles opposed to 4 moles in the reactants, the forward reaction is favoured to decrease the pressure, so more ammonia is produced.
Why isn’t pressure maximised in the Haber process?
Achieving a pressure that would lead to maximum yield would be far too expensive.
What is the effect of increased temperature on the Haber process?
As the forward reaction is exothermic, if we increase the temperature the reverse reaction is favoured as it is endothermic and decreases temperature. So to maximise yield of ammonia, temperature has to be low.
Why is temperature higher than expected in the Haber process?
At low temperature, rate of reaction would be slow even though theoretical yield would be higher, so the reaction has to be at somewhat high temperature to speed it up but to not favour the reverse reaction too.
A lower temperature would also decrease the effectiveness of the iron catalyst.
What is the effect of the iron catalyst on the Haber process?
An iron catalyst is used to speed up the rate of both the forward and reverse reaction. Therefore it does not affect yield of ammonia, but does affect rate of yield, which is an important economic consideration.
What is ammonia made in the Haber process made into to be used as a fertiliser? What is the reaction for this?
It is made into ammonium nitrate. The reaction is ammonia + nitric acid –> ammonium nitrate.
What three fertilisers can ammonia be made into? What acids does it need to react with to do this?
Ammonium nitrate using nitric acid.
Ammonium sulfate using sulfuric acid.
Ammonium phosphate using phosphoric acid.
What reaction is used to make ammonia into a fertiliser?
A neutralisation
What do NPK fertilisers stand for?
Nitrate
Phosphate
Potassium
How is ammonium phosphate produced?
Nitric acid reacts with phosphate rock to produce phosphoric acid and calcium nitrate. Then the phosphoric acid is neutralise with ammonia to produce it.
How is single superphosphate produced?
Phosphate rock is treated with sulfuric acid to produce it.
What is single superphosphate?
A mixture of calcium phosphate and calcium sulfate.
How is triple superphosphate produced?
Phosphate rock is treated with phosphoric acid.
How are potassium salts produced?
Potassium chloride and potassium sulfate are mined from the ground. They are soluble in water so they can be removed of impurities and used directly.
What is the reaction for making hydrogen for the haber process?
methane + steam –> hydrogen + carbon monoxide
What is the reversible reaction between Nitrogen and ammonia?
N2 (g) + 3H2 (g) <–> 2NH3 (g)
What is the reaction between ammonia and phosphoric acid?
Ammonia + phosphoric acid –> ammonium phosphate
What is the reaction between ammonia and sulfuric acid?
Ammonia + sulfuric acid –> ammonium sulfate
