CHAPTER 15 Flashcards
what is corrosion caused by
chemical reactions between the metal and chemicals in the environment
what is rusting
the corrosion of iron
what two conditions are needed for iron to rust
oxygen and water
why des the mass of iron increase as it rusts
the atom bond with the oxygen and water molecules which makes a compound that is heavier than iron
equation for the rusting of iron III
iron + oxygen+ water-> hydrated iron III oxide
what happens to the iron when it rusts
it is oxidised
3 ways of barriers to stop rusting
paint
oil
plastic
what is the sarcrifical method of preventing rusting
a more reactive metal is placed onto the iron so the iron stays intacts
what happens when iron is galvanised
it is covered with a layer of zinc so the oxygen and water oxidise and react with zinc and not iron
why isn’t aluminium completely destroyed by corrosion
aluminium oxide forms a protective layer that stops any further reaction taking place
why is iron completely destroyed by rusting
iron oxide is flaky and will fall off to leave more iron exposed to react again
what is an alloy
a mixture of a metal and another material
why are allows much harder than normal metals
the structure of the metal so disrupted so the layers cant slide over eachother
what is bronze made from
copper + tin
why is bronze better than copper
it is much harder
uses of bronze 3
makes medals
decorative
ornaments and statues
what is brass made from
cooper + zinc
why is brass better than bronze
it is more malleable and is used where there needs to be little friction
uses of brass 3
musical
instruments taps
door fittings
what is the most useful property of aluminium
it is low density
why is aluminium alloyed
to make it stronger
uses of aluminium alloys 2
aircraft
plating on military vehicles
why is gold alloyed
to make it stronger
why is copper mixed with gold
it is more long wearing
uses of gold alloys
jewellery
what is 24 carat gold
pure gold
how to work out how much gold is in a carat
divide by 24
what are steels
alloys of iron with carbon and other elements
what are the simplest steels
carbon steels
how are carbon steels made
most of the carbon is removed from the iron
uses of carbon steels 3
car bodies
ships
structural ships
properties of high carbon steels
strong but brittle
properties of low carbon steels 2
soft and easily shaped
what are nickel steel alloys used for and why
long span bridges , bicycle chains resistant to stretching forces
what is stainless steel made from
chromium and nickel
characteristics of stainless steel 2
don’t rust
very strong
uses of stainless steels
cutlery
cooking utensils
what do the properties of a polymer depend on
the monomers used to make it
the conditions under which the reaction happened
what are the two types of polyethene
low density polyethene
high density polyethene
how is low density polyethene made
very high
temperaatures and a catalyst
what is ld polyethene used for and why
plastic bad and bottles
it is very flexible
what gives ld polyethene its lolw density
the polymer chains are randomly branched and cant pack closely together
how is hd polyethene made
lower temperature and a different catalyst
uses of LD polyethene and why
water tanks
it is very rigid
what gives HD polyethene its high density
the polyethene chains are straighter and can pack together more closely
what are thermosetting polymers
the don’t soften when heated because of cross links between polymer chains
what are thermosoftening polymers
they soften when heated
made of individual polymer chains tangled together
what allows thermosoftening polymers to soften under heat
weak intermolecular forces between polymer chains that need little energy to overcome
when it cools the forces bring the polymer back together again
what stops thermosetting polymers from softening under heat
the monomers from covalent cross links between polymer chains which are strong an wont soften
what is glass mainly made from
sand
how is glass made
the raw materials are heated - sand limestone and sodium carbonate
they melt and react to form molten glass
when they cool, they remain in this disorganised structure
how to make different types of glass
use different raw materials
what is different about borosilicate glass and what is it used for
it has boron trioxide in it
it is used for oven ware as it has a high melting point
what are ceramics
non metal solids with high melting points that aren’t made from carbon based compounds
examples of ceramics made from clay 3
bricks crockery and toilets
how are clay ceramics made
wet clay is moulded into desired shape and heated
why do the properties of clay change so drastically when heated
there is ionic bonding between metals and non metals in clay covalent bonding
between non metals arranged in giant layers when wet water gets between layers and makes them slimy
when they are heated water is driven out and strong bonds for between layers
what are composites made from
one materials embedded in another
4 examples of composites
fibreglass
carbon fibre
concrete
wood
why is natural wood so srong
cellulose
what is a matrix in a composite
it acts as a bonder and holds everything together
what is fibreglass made from
fibre of glass embedded in a matrix made of plastic
properties of fibreglass 2
low density
very strong
what is fibreglass used for 3
skis
boats
surfboards
what is concrete made from
aggregate embedded in cement
use of concrete
buiding materials
what is carbon fibre made form
long chains of carbon atoms in plastic
carbon nanotubes in plastic
use of carbon fibres
aerospace
sports car
manufacturing
what do most fertilisers contain
nitrogen
phosphorous and potassium
why do fertilisers contain nitrogen and similar nutrients
crops grow and absorbs nutrients for growth
farmers harvets plants so little of the plant is allowed to decompose and add nutrient back into the soil
so farmers hve to replace the missing nutrients or provide more of them
even though there is a lot of nitrogen in the air why don’t plants absorb it
the gas is insoluble in water and plants can only absorb a soluble form of nitrogen
even though there is a lot of nitrogen in the air, why don’t plants absorb it
the gas is insoluble in water and plants can only absorb a soluble form of ntirogen
what is the haber process
nitrogen and hydrogen are converted to ammonia which is used in fertilisers
who created the haber process
german scientist
fritz haber
what I the most important us of ammonia
fertilisers
how is the nitrogen for the haber process sources
obtained from the air
how is hydrogen sourced for the haber process
methane is reacted with steam to form hydrogen and carbon dioxide
what are the three conditions used in the haber process
iron catalyst
high temperature
high pressure
the haber process
nitrogen and methane are sourced they are passed over an iron catalyst at high temperature and pressure
this reaction is reversible so some ammonia formed is converted back to the raw materials a dymanic equilibrium is reached. ammonia formed as a gas it is collected condensed and turned into fertiliser. the unused reactants are recycled so nothing is wasted
how is ammonia obtained from the haber process
te gases are cooled ammonia liquefies and can be separated
equation for haber process
nitrogen + hyfrogen ammonia + heat
equation for the formation of hydrogen
methane + steam-> hydrogen + carbon dioxide
why are fertilisers used
replace missing nutrients increases crop yield
crops grow faster and bigger
how to create ammonia nitrate
ammonia + nitric acid
how is ammonia phosphate formed
ammonia + phosphoric acid
when are salts formed
when acids and alkalis react together in a neutralisation reaction
is ammonia solution alkali or acid
alkali
how is ammonium nitrate formed in industry
in gaint vats high concentrations very exothermic reaction
then heat released evaporates water, leaving a very concentrated ammonium nitrate product
how is ammonim nitrate formed in the lab
smaller scale titration and crystallisation reactants are at a lower concentration less heat produced after titration, the solution is crystallised to result in pure ammonium nitrate crystals
why is crystallisation not used in industry
it is too slow
ho to make ammonium sulfate
react ammonia with sulfuric acid
what is npk fertiliser
nitogren , phosphorous and potassium fertiliser
where to source phosphorous
rocks
why is acid added to phosphorous rocks
plants cant use it as it is insoluble in water
what is produced when phosphate rock is reacted with nitric acid
phosphoric acid and calcium nitratr
what is produced when phosphate rock is react with sulfuric acid
calcium suflate and calcium phosophate also known as single superphosphate
what is produced when phosphate rock is reacted with phosphoric acid
tripe superphosphate
how is nitrogen obtained from air
air Is cooled to -200 c to liquefy it fractional distillation happens
reaction for methane+ steam
methane + steam-> hydrogen + carbon monoxide
what is the main cost of producing ammonia
sourcing the methane, which is a natural gas
why is 200 atmospheres of pressure used
there are less moles of ammonia then reactants so higher pressure - higher yield
but higher pressure is also expensive and dangerous so 200 atmospheres is a compromise
why is an iron catalyst used
it speeds up both the forward and reverse reaction doesnt affect yield of ammonia but makes it be produced quicker
what is the forward reaction of the production of ammonia
exothermic
why is 450 c used for the haber process
forward reaction is exothermic increasing temperature = less yield
bbut decreasing temperature = slower rate of reaction and minimises effect of catalyst
450 c is a compromise between maxiumum yield and speed of reaction
