chemistry: using resources (corrosion (iron corrodes easily - it rusts. …
chemistry: using resources
ceramics, composites & polymers
are non-metal solids with high melting points that aren't made from carbon-based compounds.
some can be made from clay.
when it is fired at high temperatures, it hardens to form a clay ceramic.
its ability to be moulded when wet & then hardened makes clay ideal for making pottery & bricks.
glass is a ceramic - it is generally transparent & can be moulded when hot & can be brittle when thin.
most glass is soda-lime glass which is made by heating a mixture of limestone, sand & sodium carbonate (soda) until it melts - when the mixture cools, it comes out as glass.
borosilicate glass has a higher melting point than soda-lime glass & is made in the same way using a mixture of sand & boron trioxide.
are made of one material embedded in another.
fibres or fragments of a material (reinforcements) are surrounded by a matrix acting as a binder.
the properties of a composite depend on the properties of the materials it is made from.
consists of fibres of glass embedded in a matrix made of polymer (plastic) - it has a low density (like plastic) but is very strong (like glass) & is used for e.g. skis, boats & surfboards.
composites have a polymer matrix, the reinforcement is either made from chains of carbon atoms bonded together (carbon fibres) or from carbon nanotubes.
these composites are very strong & light so are used in aerospace & sports car manufacturing.
is made from aggregate (mixture of sand & gravel) embedded in cement & is very strong, making it ideal for use as a building material.
is a natural composite of cellulose fibres held together by an organic polymer matrix.
is made &
it is made from influence its properties
e.g.the properties of poly(ethene) depend on the catalyst that was used & the reaction conditions (temperature & pressure) that it was made under.
low density (LD) poly(ethene) is made from ethene at a moderate temperature under a high pressure & with a catalyst - it is flexible & used for bags & bottles.
high density (HD) poly(ethene) is made from ethene but at a lower temperature & pressure with a different catalyst - it is more rigid & is used for water tanks & drainpipes.
the monomers that a polymer is made from determine the type of bonds that form between polymer chains - these weak bonds between the different molecule chains determine the properties of a polymer:
contain individual polymer chains entwined together w/ weak forces between the chains - these plastics can be melted & remoulded.
contain monomers that can form cross-links between polymer chains, holding the chains together in a solid structure - they do not soften when heated so are strong, hard & rigid.
properties of materials
what materials are used for depends on their properties
: glass & clay ceramics: porcelain, bricks
insulators of heat & electricity
brittle (not flexible + break easily)
: many applications in clothing & insulators in electrical items.
insulators of heat + electricity
flexible (bent without breaking)
: properties depend on the matrix/binder & the reinforcement used so have many different uses.
: many uses inc. electrical wires, car body-work, cutlery
good conductors of heat + electricity
ductile (can be drawn into wires)
the regular structure of
- often too soft for use in everyday life
- add another element to the metal - disrupts the structure of the metal --> alloys are harder than pure metals
alloys of iron:
- used instead of pure iron
made by adding small amounts of carbon + sometimes other metals to iron.
= copper + tin
bronze harder than copper
= copper + zinc
more malleable than bronze
used where lower friction required; water taps, door fittings
used to make jewellery: pure gold is very soft so metals e.g. zinc, copper, silver used to harden the gold
pure gold 24 carat so 18 carat 75%
are used to make aircraft: aluminium has a low density - important in aircraft manufacture. pure aluminium too soft for making aeroplanes so it's alloyed with small amounts other metals to make it stronger.
where metals react with substances in their environment + are gradually destroyed.
only happens on the surface of a material where it's exposed to the air.
corrodes easily - it
needs to be in contact with both oxygen & water - present in the air.
iron + oxygen + water --> hydrated iron(III) oxide
rust is a soft crumbly solid that flakes off to leave more iron available to rust again so eventually all the iron corrodes away even if it wasn't initially at the surface.
corrodes when exposed to air but isn't completely destroyed (unlike iron) as aluminium oxide that forms when aluminium corrodes doesn't flake away + forms a protective layer that sticks firmly to the aluminium below + stops any further reaction taking place.
put an iron nail in a boiling tube with just water, it won't rust (water boiled to remove oxygen + oil used to stop air getting in.)
put an iron nail in a boiling tube with just air, it won't rust (calcium chloride used to absorb any water from the air)
put iron nail in a boiling tube with air and water, it will rust.
the mass of a rusty nail will increase as the iron atoms in the nail bond to oxygen & water molecules, resulting in a compound that is heavier than iron alone.
the iron with a
to keep out the water & oxygen
painting/coating with plastic - ideal for big + small structures + can be decorative.
electroplating - uses electrolysis to reduce metal ions onto an iron electrode, can be used to coat the iron with a layer of a different metal that won't be corroded away.
oiling/greasing - used when moving parts are involved like on bike chains.
method - placing a more reactive metal e.g.zinc or magnesium with the iron so water & oxygen react with the sacrificial metal instead of with the iron.
object can be
by spraying it with a coating of zinc. the zinc layer is firstly protective but if scratched, the zinc around the site of the scratch works as a sacrificial metal.
finite + renewable resources
resources form without human input + include anything that comes from the earth, sea or air e.g. cotton for clothing or oil for fuel.
some natural products can be
products or improved upon by man-made processes e.g. rubber is a natural product extracted from the sap of a tree but man-made polymers can replace rubber in uses such as tyres.
provides conditions where natural resources can be enhanced for our needs e.g. the development of fertilisers allow us to produce a
resources reform at a similar rate to, or faster than, they are used.
is renewable as trees can be planted following a harvest + only take a few years to regrow
(non-renewable) resources aren't formed quickly enough to be considered replaceable
nuclear fuels e.g. uranium & plutonium
minerals & metals found in ores in the earth
after being extracted, many finite resources undergo
to provide fuels & materials necessary for modern life e.g. fractional distillation produces usable products e.g. petrol from crude oil & metal ores are reduced to produce a pure metal.
risks to extracting finite resources
many modern materials are made from raw, finite resources e.g. plastics, metals + building materials.
the social, economic & environmental effects of extracting them have to be balanced.
e.g. mining metal ores is good as useful products can be made + it provides local people with jobs + brings money into the area but mining ores is bad for the environment as it uses lots of energy, scars the landscape, produces lots of waste + destroys habitats.
reuse & recycling
development is an approach to development that takes account of the needs of present society while not damaging the lives of future generations.
not all resources are renewable so it's unsustainable to continue using them.
using resources + extracting them can be unsustainable due to the amount of energy used + waste produced.
processing the resources into useful materials e.g. glass + bricks can be unsustainable as the processes use energy made from finite resources.
reducing the use of finite resources is for people to use less - reduce the use of that resource + anything needed to produce it.
the use finite resources can't be stopped altogether but chemists can develop + adapt processes that use lower amounts of finite resources + reduce damage to the environment e.g. catalysts developed that reduce the amount of energy required for certain industrial processes.
copper is a finite resource so its sustainability can be improved by extracting it from
ores (can be used for other metals too)
- bacteria convert copper compounds in the ore into soluble copper compounds, separating out the copper from the ore in the process. The leachate (solution produced by the process) contains copper ions, which can be extracted e.g. by electrolysis or displacement with a more reactive metal e.g. scrap iron.
- growing plants in soil that contains copper. the plants can't use or get rid of the copper so it gradually builds up in the leaves. the plants can be harvested, dried + burned in a furnace. the ash contains soluble copper compounds from which copper can be extracted by electrolysis or displacement using scrap iron.
mining + extracting metals uses lots of energy, most of which comes from burning fossil fuels. recycling
uses less energy + conserves the finite amount of each metal in the earth + reduces the amount of waste sent to landfill.
metals are recycled by melting them then casting them into the shape of the new product.
depending on what the metal will be used for, the amount of separation required for recyclable metals can change e.g. waste steel & iron can be kept together as they can both be added to iron in a blast furnace (used to extract iron its ore at a high temp. using carbon) to reduce the amount of iron required.
recycling helps sustainability by reducing the amount of energy needed to make new glass products + the amount of waste created when used glass is thrown away.
glass bottles can often be reused without reshaping.
other forms of glass can't be reused so they are recycled instead - the glass is separated by colour & chemical composition before being recycled.
the glass is crushed then melted to be reshaped for use in glass products e.g. bottles, jars. it may be used for a different purpose e.g. insulating glass wool for wall insulation in homes.
life cycle assessments (LCA)
looks at every stage of a product's life to assess the impact it would have on the environment.
getting the raw materials:
extracting raw materials needed can damage the local environment e.g. mining metals. extraction can result in pollution due to the amount of energy needed.
raw materials often need to be processed to extract the desired material - needs large amounts of energy e.g. extracting metals from ores or fractional distillation of crude oil.
manufacture + packaging
^^ use a lot of energy resources + can cause a lot of pollution e.g. harmful fumes e.g. carbon monoxide or hydrogen chloride.
waste products + how to dispose of them needs to be thought about - the chemical reactions used to make compounds from their raw materials can produce waste products - some waste can be turned into other useful chemicals, reducing the amount that ends up polluting the environment.
using the product
^^ can damage the environment e.g. burning fuels releases greenhouse gases + other harmful substances. fertilisers can leach into streams + rivers causing damage to the ecosystems.
how long a product is used for or how many uses - products that need a lot of energy to produce but are used for ages mean less waste in the long-term.
products are often disposed of in landfill sites - takes up space + pollutes the land + water e.g. if paint washes off a product + gets into rivers.
energy is used to transport waste to landfill which causes pollutants to be released into the atmosphere.
products might be incinerated -- air pollution.
the use of energy, some natural resources + the amount of certain types of waste produced by a product over its lifetime can be easily quantified but the
of some pollutants is
harder to give a numerical value
to e.g. it is difficult to apply a value to the negative visual effects of plastic bags in the environment compared to paper ones.
so producing an LCA is a
method as it takes into account the values of the person carrying out the assessment so LCAs can be
(only show some of the impacts of a product on the environment) can be biased as they can be written to deliberately support the claims of a company in order to give them
plastic vs paper bags
even though plastic bags aren't biodegradable, they take less energy to make + have a longer lifespan so may be less harmful to the environment.
plastic bag LCA:
raw materials: crude oil
manufacturing + packaging: compounds needed to make the plastic are extracted from crude oil by fractional distillation, followed by cracking then polymerisation. waste is reduced as other the fractions of crude oil have other uses.
using product: reusable + can be used for others things as well as shopping e.g. bin liners.
product disposal: recyclable but not biodegradable + will take up space in landfill + pollute land.
paper bag LCA:
raw materials: timber
manufacturing + packaging: pulped timber is processed using lots of energy + lots of waste is made.
using: usually only used once
disposal: biodegradable, non-toxic + can be recycled.
water that has been treated or is naturally safe for humans to drink - essential for life.
not chemically pure as pure water only contains H2O molecules whereas potable water can contain other dissolved substances.
levels of dissolved salts aren't too high
the pH is between 6.5 and 8.5
there aren't any microbes (e.g. bacteria) in it.
rain water is a type of fresh water (doesn't have much dissolved in it). when it rains, water collects as surface water (lakes, rivers, reservoirs) or as groundwater (in rocks - aquifers - that trap water underground)
UK: source of fresh water depends on location. surface water tends to dry up first so in warm areas e.g. south-east most of domestic water supply comes from groundwater.
fresh water only has low levels of dissolved substances in it but still needs to be treated to make it safe before it can be used.
: a wire mesh screens out large objects + then gravel + sand beds filter out any other solid bits.
: water sterilised to kill any harmful bacteria or microbes - bubble chlorine gas through it or use ozone or ultraviolet light.
chemicals can be added to the water supply e.g. fluoride (good for teeth) but is controversial as people aren't given a choice over whether they consume them or not.
in dry countries there isn't enough surface or groundwater so
is used instead - treated by
used to desalinate sea water:
of water using a pH meter - needs to be neutralised if too high/low with a titration but use a pH meter to tell when solution neutral rather than an indicator as it won't contaminate the water.
water for the
presence of sodium chloride
(the main salt in seawater) - do a flame test on a small sample to test for sodium ions --> yellow. chloride ions - add a few drops of dilute nitric acid to sample then a few drops of silver nitrate solution --> white precipitate.
the water, pour the salty water into a distillation apparatus, heat the flask from below, the water will boil + produce steam, leaving any dissolved salts in the flask. the steam will condense back to liquid water in the condenser + can be collected as it runs out.
retest for sodium chloride
in the distilled water to check that it has been removed +
retest the pH
with a pH meter to check it's neutral (7).
seawater can be treated by processes that use
- salty water passed through a membrane that only allows water molecules to pass through - ions + larger molecules are trapped by the membrane so are separated from the water.
distillation + reverse osmosis require loads of
+ not practical for producing large quantities of fresh water.
waste water treatment
water used for having a bath, using the toilet, washing-up etc -- flush down drain --> sewers --> sewage treatment plants
agricultural systems produce a lot of waste water including nutrient run-off from fields & slurry from animal farms.
sewage from domestic or agricultural sources has to be treated to remove any organic matter & harmful microbes before put back into fresh water sources like rivers or lakes otherwise it would make them very polluted + would pose health risks.
industrial processes e.g. the Haber Process produce a lot of waste water that has to be collected + treated.
industrial waste water contains harmful chemicals (as well as organic matter) so it has to undergo additional stages of treatment before it is safe to release it into the environment.
to remove large bits of material (twigs, plastic bags) and any grit.
the sewage is left to stand in a
- the heavier suspended solids sink to the bottom to produce
while the lighter
floats on the top.
in the settlement tank is removed + treated by
biological aerobic digestion
- air is pumped through the water to encourage aerobic bacteria to break down any organic matter - including other microbes in the water.
from the bottom of the settlement tank is removed + transferred into large tanks where it's broken down by bacteria through
which breaks down the organic matter in the sludge, releasing
which can be used as an energy source + the remaining digested waste can be used as a
for waste water containing toxic substances, additional stages of treatment may involve adding chemicals (e.g. to precipitate metals), UV radiation or using membranes.
sewage treatment requires more processes than treating fresh water but uses less energy than the desalination of salt water so could be used as an alternative in areas where there isn't much fresh water e.g. Singapore treats waste water + recycles it back into drinking supplies but people don't like the idea of drinking water that used to be sewage.
the Haber Process
nitrogen + hydrogen ⇌ ammonia (+ heat)
N2 (g) + 3H2 (g) ⇌ 2NH3 (g)
suited for an industrial scale as the reactants aren't too difficult or expensive to obtain.
nitrogen: obtained from the air (as it's 78% N2)
hydrogen: from reacting methane (from natural gas) with steam to form hydrogen + carbon dioxide
reactant gases passed over an iron catalyst.
a high temperature (450ºc) & high pressure (200 atmospheres) are used.
the iron catalyst makes the reaction go faster but doesn't affect the yield.
the reaction is reversible so some of the ammonia produced converts back into hydrogen & nitrogen again. eventually reaches a dynamic equilibrium.
the ammonia is formed as a gas but as it cools in the condenser it liquefies + is removed. the unused hydrogen & nitrogen are recycled so nothing is wasted.
the ammonia produced can be used to make ammonium nitrate - a nitrogen-rich fertiliser.
conditions such as temp. & pressure affect the rate of reaction + affect the position of equilibrium so there can be trade-off between increasing the rate + maximising the yield.
the forward reaction in the Haber process is exothermic so increasing the temperature will move the equilibrium the wrong way (towards the N2 & H2) so the yield of ammonia would be greater at lower temperatures but lower temp.s mean a slower rate of reaction (& so equilibrium is reached more slowly).
450ºc is a compromise between maximum yield & speed of reaction.
higher pressures move the position of equilibrium towards the products since there are less molecules of gas there so increasing the pressure maximises the percentage yield & increases the rate of reaction.
the pressure is set as high as possible without making the process too expensive or dangerous to build + maintain -- 200 atm.
farmers used to use manure to fertilise fields but formulated fertilisers are better as:
they're more widely available
easier to use
don't smell (odourless)
have the right amount of each nutrient
so more crops can be grown.
NPK fertilisers are
containing salts of nitrogen, phosphorus & potassium in the right percentages.
nitrogen, phosphorus, potassium -- if plants don't get enough of these elements, their growth + life processes are affected -- these elements may be missing from the soil if they've been used up by a previous crop.
fertilisers replace these missing elements or provide more of them, helping to increase the crop yield as the crops can grow faster + bigger e.g. fertilisers add more nitrogen to plant proteins, making them grow faster - increasing productivity.
ammonia can be reacted with oxygen & water in a series of reactions to make nitric acid.
ammonia can be reacted with acids (including nitric acid) to get ammonium salts.
ammonia & nitric acid react together to produce ammonium nitrate - good compound to use in a fertiliser as it has nitrogen from two sources.
ammonia + nitric acid --> ammonium nitrate
NH3 (aq) + HNO3 (aq) --> NH4NO3 (aq)
the reaction is carried out on a much smaller scale by titration + crystallisation.
the reactants are at a much lower concentration so less heat is produced + it's safer for a person to carry it out.
after the titration the mixture needs to be crystallised to give pure ammonium nitrate crystals.
crystallisation isn't used in industry as it's very slow.
the reaction is carried out in giant vats at high concentrations resulting in a very exothermic reaction.
the heat released is used to evaporate water from the mixture to make a very concentrated ammonium nitrate product.
potassium chloride & potassium sulphate can be mined & used as a source of potassium.
phosphate rock is also mined but as the phosphate salts in the rock are insoluble, plants can't use them as nutrients so the phosphate rock is reacted with a number of different types of acids to produce soluble phosphates.
with nitric acid --> phosphoric acid & calcium nitrate
with sulfuric acid --> calcium sulfate + calcium phosphate (this mixture is single superphosphate).
with phosphoric acid --> calcium phosphate -- triple superphosphate.