C15 Using our resources Flashcards
what is rusting?
the corrosion of iron or steel
what conditions are needed for iron or steel to rust?
oxygen and water
what is the chemical name for rust?
ruse = hydrated iron (III) oxide
word equation for the rusting of iron
iron + oxygen + water -> hydrated iron (III) oxide
what is done to iron or steel to prevent them from rusting?
preventing water and oxygen from reaching the iron/steel by coating it with either:
- paint,
-a more/less reactive metal,
- oil or grease,
- plastic.
how does rust spread?
- rust forms,
- it is soft and flakes off the iron/steel,
- exposing more iron/steel to the oxygen and water,
- so more of it rusts.
what is sacrificial protection? why does it work?
sacrificial protection: coating iron/steel with a more reactive metal which reacts with the oxygen and water instead of the iron/steel itself, preventing it from rusting.
works because the more reactive metal has a stronger tendency than the iron/steel to give away electrons and form positive ions.
what is galvanisation?
coating iron/steel with zinc which is more reactive, so sacrificially protects it from rusting.
when is sacrificial protection often used?
- used under harsh conditions e.g. in seawater,
- protecting underground pipes,
- when coating is likely to be scratched, e.g. commercial wheelie bins
give 2 alloys that are made using copper and one other metal
- copper and zinc alloy makes brass,
- copper and tin alloy makes bronze.
which 2 metals is bronze an alloy of?
what is it used for? why?
BROCT
- bronze is an alloy of copper and tin,
- used for statues, decorative items, ship propellers,
- because of its toughness and resistance to corrosion.
what is steel?
an alloy of iron with carbon and/or other elements
which 2 metals is brass an alloy of?
what is it used for? why?
BRACZ
- brass is a alloy of copper and zinc,
- used for taps, musical instruments and door fittings,
- because it is hard but workable: can be hammered into thin sheets and pressed into shapes.
give a property of aluminium alloys
low density
why are copper, aluminium and gold often alloyed with other metals?
to make them harder
why is gold often alloyed with copper?
so that it wears away more slowly
what is corrosion?
the destruction of materials by chemical reactions with substances in the environment
how to measure the proportion of gold in an alloy
divide the carat number by 24: e.g. 24 carat gold is 100% (pure), 18 carat gold is 75% gold.
describe the difference between the properties of low and high carbon steel
low carbon steel: softer and more easily shaped
high carbon steel: strong and brittle.
uses of aluminium alloys
lightweight alloys: aircraft
other aluminium alloys: armour plating on tanks and other military vehicles.
what are stainless steels alloys of?
what are their properties?
stainless steels:
- alloys of steel with chromium and nickel,
- hard, strong, the only steels which are resistant to corrosion.
what are stainless steels often used for
and why?
- often used for reaction vessels,
- because they are hard and strong, so withstand high pressures and temperatures,
- and are resistant to corrosion, so withstand corrosive chemicals.
what do the properties of a polymer depend on?
- the monomers they are made from,
- the conditions of the reaction used to create it.
what is the difference between properties of thermosoftening and thermosetting polymers?
thermosoftening polymers melt when heated
whereas thermosetting polymers do not.
what is the difference between the structures of of thermosoftening and thermosetting polymers?
thermosoftening polymers: tangled up individual polymer chains, weak intermolecular forces between them, easily separated.
thermosetting polymer chains:strong covalent bonds between polymer chains, forming cross-links.
what happens to a thermosoftening polymer when heated?
- when heated, the weak intermolecular forces between polymer chains are broken,
- so the polymer softens, melts.
what happens to a thermosetting polymer when heated?
- the strong covalent bonds which form cross-links between polymer chains mean that the chains cannot be separated,
- thus the polymer does not soften/melt,
- but can char at high enough temperatures.
what is the most common type of glass
and what is it made from?
soda-lime glass
made with a heated mixture of sand, limestone and sodium carbonate
what is borosilicate glass made of?
which of its properties is different from soda-lime glass’?
borosilicate glass:
- made of sand and boron trioxide,
- heats at higher temperatures than soda-lime glass.
describe the arrangement of particles in glass and how it forms
- as the heated raw materials cool down and solidify, the particles become set in place in a random arrangement.
how are clay ceramics made?
by moulding wet clay then heating it in a furnace
what is clay made of?
clay contains compounds of metals and non-metals
describe the bonding in dry clay
(before being wet and fired)
- clay contains compounds of metals and non-metals,
- there is ionic bonding between metal and non-metal ions,
- and some covalent bonding between non-metal atoms,
- the ions and atoms are arranged in giant, layered structures.
describe how bonding changes in wet clay as it is fired
and how this affects its properties
- water molecules between the layers of ions and atoms are driven out,
- so strong bonds form between the layers of the giant structure,
- making the clay brittle,
- because a sharp blow can distort the layers in its structure so that like-charged ions become adjacent and repel from each other, cracking the ceramic object.
what is a composite usually made of?
what is the name of this process?
one material surrounding and binding together the fragments of another (reinforcement), forming a product with improved properties for a particular use.
give 4 examples of composites
glass-ceramic composite
fibreglass
plywood
concrete
give 2 materials that can bind to ceramics to make a composite
glass (glass-ceramic composites)
polymers
why do farmers add fertiliser to soil?
to replace the nitrogen and nutrients lost from the soil when they take crops from it
why do plants need nitrogen?
to make proteins for growth
why can’t plants take in nitrogen gas from the air?
nitrogen gas in the air is insoluble in water
plants can only take in a soluble form of nitrogen
what is ‘fixing’ nitrogen?
turning nitrogen gas in the air into nitrogen compounds that plants can absorb in solution
what is the purpose of the Haber process?
to turn nitrogen gas into ammonia which can be turned into nitrogen that is soluble in water and absorbable by plants
what are the raw materials for the Haber process?
nitrogen from the air
hydrogen, mainly from natural gas
describe the steps of the Haber process
- pass nitrogen and hydrogen over a CATALYST at HIGH TEMP (around 450 degrees C) and HIGH PRESSURE (around 200 atmospheres),
- which produces AMMONIA,
- some ammonia gas formed breaks down again into hydrogen and nitrogen because the reaction is REVERSIBLE,
- remove ammonia by COOLING THE GASSES so that AMMONIA LIQUIFIES and can be separated from unreacted nitrogen gas and hydrogen gas,
- RECYCLE UNREACTED HYDROGEN and NITROGEN GAS, recompress and reheat them, then return them to the reaction vessel so that they can react again to form ammonia.
how is money spent to obtain the raw materials for the Haber process?
- costs money to separate nitrogen from other gases in the air by fractional distillation for use,
- costs money to produce the hydrogen gas by reaction of methane with steam.
symbol equation for haber process
N2(g) +3H2(g) ⇌ 2NH3(g)
how does increasing pressure affect the products of the Haber process? why?
- the reaction is reversible so le chateliers principle applies:
- reaction tries to counter change,
- so point of equilibrium shifts to side with less pressure,
- which here is to the right because there are less molecules of ammonia than there are reactants,
- so more ammonia is produced.
why is 200 atmospheres a compromised pressure for the haber process?
- reduces costs of equipment and energy needed for higher pressures,
- reasonable rate of reaction,
- not maximum possible yield.
why is 450 degrees C a compromised temperature for the haber process?
- a lower temperature would give a higher yield of ammonia,
- but a high temperature like this gives a reasonable rate of reaction due to more successful and energetic collisions of gas molecules,
- and high temperature makes the catalyst more reactive.
how would lower temperature give more ammonia in the Haber process?
- reaction is reversible so le chatelier’s principle applies: reaction tries to counter change,
- forward reaction is exothermic, increases temperature of surroundings,
- so the product of the forward reaction (ammonia) is increased to counter the lowered temperature of the surroundings.
is ammonia acidic or alkaline?
alkaline
ammonia can be used to make nitric acid, which is then used to make what
nitric acid + ammonia -> ammonium nitrate (fertiliser)
what are NPK fertilisers?
NPK fertilisers: formulations containing mixtures of nitrogen, potassium and phosphorus compounds that help plants grow healthily
what can ammonia be used to produce
ammonia salts
and nitric acid
how is phosphorus used in NPK fertilisers obtained?
from dug-up phosphate-containing rock
and treated with acid to make soluble fertiliser salts
which acids is phosphate rock treated with? why?
nitric acid
sulfuric acid
because phosphate rock itself is insoluble, but when treated with these acids produces salts which are soluble therefore can be used as fertilisers
how is potassium for NPK fertilisers obtained?
from potassium sulfate and potassium chloride dug from the ground
does potassium need to be treated before use as fertiliser? why?
no
potassium compounds are already soluble in water so can be used directly as fertiliser (once separated from impurities)
what does phosphate rock produce when treated with nitric acid?
ammonium nitrate
what does phosphate rock produce when treated with sulfuric acid?
a single superphosphate
what does phosphate rock produce when treated with phosphoric acid?
calcium phosphate
