C15: Using our resources Flashcards
how does corrosion occur
caused by chemical reactions between the metal and substances in the environment
rusting
corrosion of iron
what is the equation for rusting
iron + oxygen + water -> hydrated iron (III) oxide
what can we coat iron in to prevent rusting ?
-paint with rust inhibitors
-oil or grease
-plastic
-more reactive metal
-less reactive metal
how can we coat iron in different metals (2)?
dipping in molten metal
electroplating
what is it called when iron is coated in zinc
galvanising
how does galvanising work
the zinc is more reactive than the iron, the water or oxygen reacts with the zinc instead
what is galvanising an example of
sacrificial protection (zinc is sacrificed to protect the iron)
what metals can also be used for sacrificial protection
aluminium or magnesium
what is an alloy
a mixture of metals created for a useful reason
why are alloys harder to break
the different sized metal ions make it harder for the layers to slip
copper and tin alloy
bronze
copper and zinc alloy
brass
what can aluminium alloys be used for
aircraft , armour plates (they are lightweight)
how can we find the fraction of gold in the jewellery
divide the carat by 24
what are steels an alloy of
iron and carbon and/ or other elements
what are the simplest steels called
carbon steels
cheap to make
used in cars, ships ect.
what’s useful about stainless steel
it is resistant to corrosion
what do we mix with steel to make stainless steel
chromium and nickel
high carbon steel
very hard but brittle
what are the two types of poly(ethene)
high density (HD)
low density (LD)
how is LD poly(ethene) formed
high pressure and a trace of oxygen.
polymer chains are random and cannot pack closely together
how is HD poly(ethene) formed
catalyst at 50 degrees and a slightly raised pressure.
straighter poly(ethene) chains, packed closely together
differences between LD and HD
-HD has higher softening temperature
-HD is stronger
what are thermosoftening polymers
they soften easily when heated, and re-set when they cool down
what are thermosetting polymers
they do not melt when heated, due to strong covalent bonds ‘cross-linking’
why do thermosoftening polymers melt
weak intermolecular forces between polymer chains
what will happen to a thermosetting polymer if it gets too hot
it will char
what is soda-lime glass made of (most common glass)
sand, limestone, sodium carbonate (soda)
properties of ceramics
-hard
-brittle
-good electrical insulators
-resistant to chemical attack
what is clay made of
metals and non-metals with ionic bonding between ions, and covalent between non-metal ions
what are the two materials a composite is made of
- a matrix that binds the other material
-another material
what do composites do
bind the two materials together (reinforcement) and improve a desirable property that neither original material can offer alone
examples of composites
-glass-ceramic
-fibreglass
-plywood/MDF
-concrete
what is ammonia’s formula
NH(3)
why do plants need nitrogen
it helps them make proteins
why do plants not get enough nitrogen
the nitrogen in the air is insoluble in water and cannot be absorbed
what is the process that turns nitrogen gas into ammonia
the Haber process
ammonia’s most important use
fertilisers
what is the Haber process:
-nitrogen and hydrogen purified, passed over an iron catalyst at about 450 degrees and 200 atmospheres
-the reaction is reversible
-ammonia removed by cooling gases so that it liquefies.
-separated from unreacted nitrogen and hydrogen
what happens to the unreacted nitrogen and hydrogen in the Haber process
recycled back into the reaction mixture, the process happens again
why is nitrogen in the air not a free resource
we have to separate it using fractional distillation, requiring energy
how is the hydrogen made for the Haber process
reacting methane gas with steam at high temperatures
methane +steam -> hydrogen + carbon monoxide
what is the main cost of the Haber process
buying methane gas, bought as a natural gas (fossil fuel)
how else can methane create hydrogen
mixing with air and oxygen, leaving mainly nitrogen in the air
increase in pressure will do what in the Haber process
shift the equilibrium to the right, producing more ammonia
why do we use 200 atmospheres in the Haber process
need a pressure as high as possible, but also reasonably priced. this is a compromise
what does lowering the temperature do in the Haber process
shift the equilibrium to the right and increase ammonia
why do we use 450 degrees with the Haber process
we need a low temperature, but too low would mean the reaction happens slow and this would be expensive. this is a compromise
too low a temp would reduce the iron catalyst’s effectiveness
what three fertilisers can ammonia solution create
ammonium nitrate
ammonium sulfate
ammonium phosphate
ALL BY ADDING ACIDS
is ammonia acid or alk
alk
ammonia solution forming new fertilisers is an example of what
neutralisation reaction
what three minerals do plants need
nitrogen, potassium and phosphorus
what is a fertiliser that has all the minerals needed for a plant
the NPK fertiliser
how to get phosphorus for NPK
dug out from rock, treated with nitric, sulfuric and phosphoric acid, making triple superphosphate in the end
how do we get potassium for NPK
dug from the ground
how do we get nitrogen for NPK
ammonium solution
