Ch15 Using our resources Flashcards
Corrosion
destruction of materials by chemical reactions with substances in the environment
Rusting
corrosion of iron
oxygen and water are necessary for it to take place
iron + oxygen + water -> hydrated iron(III) oxide
Preventing rust
coating the iron with a barrier:
grease/oil
plastic
electroplating
paint
Aluminium rusting
doesn’t happen
- has an aluminium oxide coating that protects the metal from corroding
Using a more reactive metal to prevent rusting
molten metal or electroplating
example- zinc is used to galvanise iron
zinc reacts with oxygen instead, losing electrons and becoming oxidised
sacrificial protection
Copper alloys
Bronze -> copper + tin
Brass -> copper + zinc
Aluminium alloy properties
low density
lightweight but strong
- used to build aircraft
- used as armour plating on military vehicles
Bronze uses
toughness and resistance to corrosion
used for
- statues and decorative items
- ship propellers
Brass uses
hard can be hammered into shapes and pressed into intricate shapes used for - musical instruments - door fittings and taps
Gold alloys
usually alloyed with copper, silver and zinc to make jewellery
proportion of gold in the alloy is measured in carats
24 carat being 100% pure gold
Steel
alloy of iron + carbon and other metals
low- carbon steels
removing carbon from the iron obtained from a blast surface
soft and easily shaped
used in machinery
high-carbon steel
strong but brittle
nickel-steel alloy
resistant to stretching forces
used for drill bits
stainless steels
chromium + nickel
hard
resistant to corrosion
used for cooking utensils and reaction vessels
thermosoftening polymers
soften easily and then re-set when they cool down
made up of individual polymer chains tangled together
easy to separate
weak intermolecular forces
thermosetting polymers
don’t melt when heated
have strong covalent bonds forming ‘cross-links’ between polymer chains
rigid
don’t soften
properties of polymers depend on…
monomers used to create it
conditions chosen to carry out the reaction
low density poly(ethene)
made from ethene monomers
uses high pressure and a trace of oxygen
polymers are randomly branched and cannot pack closely together
high density poly(ethene)
made from ethene monomers uses a catalyst at 50°C at a slightly raised pressure straight chains packed closer higher softening temp stronger
Soda- lime glass
made by heating a mixture of sand, limestone and sodium carbonate
random arrangement of particles
Borosilicate glass
made from sand and boron trioxide
melts at high temperatures than soda-lime glass
used for ovenware
Ceramics
made from shaping wet clay
- made from aluminium and potassium
- silicon and oxygen
heated in a furnace so the water evaporates and strong bonds form between layers
Ceramic properties
brittle
- sharp blow distorts layers in structure
- ions with like charges repel each other, cracking the ceramic object
composites
made of two materials
has improved properties
reinforcement
a matrix(a binder) of one material surrounding and binding together fibres or fragments of the other material
examples of composites
concrete
- cement, sand and gravel mixed with water
- very hard
- strong in compression
- can be set around matrix of steel rods
plywood
- thin sheets of wood glue together with successive layers of grain at right angles
Haber process
- nitrogen in the air
- hydrogen from methane
- gases are purified
- passed over an iron catalyst at high temp(450°C) and high pressure(200 atmospheres)
- some hydrogen and ammonia react to form ammonia
N2 + 3H2 -> 2NH3 - ammonia is then removed- cooling the gases so the ammonia liquifies and is then separated from the unreacted N and H gas which have higher bp
- unreacted hydrogen and nitrogen are recycled back into the reaction mixture
Haber reversible reaction
ammonia gas breaks down into hydrogen and nitrogen
NPK fertilisers
plants need nitrogen to grow(make proteins)
- have to use Haber process to change nitrogen gas into ammonia because plants can only absorb soluble form
phosphorous
potassium
making hydrogen for Haber process
methane + steam -> hydrogen + carbon monoxide
at very high temp
making nitrogen for Haber process
fractional distillation of liquid air (cooled to -200°C)
Economics of Haber process
energy cost to liquefy and compress air
costs for heating water
methane gas is expensive
maximum yield of ammonia
make pressure high as possible to shift
(volume of reactants > vol of products)
decreasing temp
-slower rate of reaction(expensive)
iron catalyst
phosphorous treated with nitric acid
produces phosphoric acid and calcium nitrate
phosphoric acid is then neutralised with ammonia to produce ammonium phosphate
phosphorous treated with sulfuric acid
produces superphosphate
- mixture of calcium phosphate and calcium sulfate
phosphorous rock treated with phosphoric acid
produces triple superphosphate
- calcium phosphate
sources of potassium
potassium sulfate and potassium chloride mined from the ground
fertilisers
- ammonia + phosphoric acid -> ammonium phosphate
- ammonia + sulfuric acid -> ammonia sulfate
- ammonia + nitric acid -> ammonium nitrate
