resources that are being used upfaster than they can be made eg. crude oil, limestone, metal ores
renewable resources
resources that can be replaced at the same rate that they are used up eg. biofuels
sustainable development
development which meets the needs of current generations without compromising the needs of future generations
Synthetic (man-made) Alternatives:
Polyester: alternative to cotton and wool, can be used in clothes
Polymers: alternative to rubber, can be used in tyres
MDF (medium-density fibreboard): alternative to wood, can be used in construction
Reasons for Estimating using Order of Magnitude:
Can be uncertainty when estimating
Rate of future consumption is uncertain
Possibility of discoveringnew deposits
New technologies could burnmorefossil fuels
potable water
impure water that is safe to drink, containing low levels of dissolved salts and microbes, a pH between 6.5 and 8.5 and not containing any microorganisms
fresh water
found in lakes, rivers, ice caps, glaciers, underground streams and aquifers; contains low levels of dissolved salts and microbes
ground water
found in underground streams and aquifers; contains low levels of dissolved salts and ordinary levels of microbes
sea water
found in the sea; contains high levels of dissolved salts and microbes
waste water
produced through homes, industry and agriculture; contains high levels of dissolved salts and microbes
pure water
water not containing dissolved salts or microbes
Water Treatment Plant (used for fresh and ground water):
Wire meshfilters out large solids
Gravel or sandfilter bedsremovesmall insoluble solids
Disinfectingsterilises by killing bacteria
Adding fluoride improves dental health
Methods of Sterilisation:
Chlorine gas: dissolves in water to kill microorganisms as it is a powerful oxidising agent - it is toxic and has evaporated by the time it reaches us
Ozone (O3): made by exposing oxygen to sparks; not as soluble as chlorine but is an equally powerful oxidising agent and isn't toxic (Equation: 3O2-spark-2O3)
Ultraviolet (UV) light: causes mutations in the bacteria's DNA so they can't replicate and therefore die out - not as effective as other methods
Desalination Methods (used on sea water):
Distillation: water is boiled in boiling chamber and it evaporates then condenses in the condensing dome - requires a lot of energy
Reverse Osmosis: external pressure is used to force water through a semi-permeable membrane to separate salts - requires energy but not as much as distillation
Both processes are expensive
Waste water treatment:
Sewage sent through pumping station
Screening grit removes large solids
Primary sedimentation splits sewage into sludge containing human waste (solid) and effluent (liquid)
Effluentdigested aerobically, sterilised and released into rivers or as drinking water - rapidly breaks biomass into CO2, O2; requires lots of energy as oxygen is bubbled through sewage at an ambient temperature
Sludgedigested anaerobically at 36°C over 30 days - biomass broken down into CH4 which is used as fuel as it is rich in minerals and has no pathogens as well as CO2, H2O
Why treat waste water?
Contains large amounts of microbes allowing the spread of pathogens such as cholera
Contains high levels of nitrates, phosphates and other minerals that promote excessive algae growth leading to eutrophication as the algaecompete with and kill other water based plants
Bioleaching Copper:
Ore containing 0.1% of CuFeS2
Orecrushed to a fine powder
Water and bacteria are added and left in a tank for 6days
CuFeS2 is oxidised to CuSO4, which is soluble
The solution of CuSO4 is collected and electrolysed
Pure copper is obtained
Mining and Smelting of Copper:
Copperore is mined from earth
Copperore is heated in a furnace with carbon (smelting), which produces impure copper
The copper is purified by electrolysis
Pure copper is produced
Copper Purification: Electrolysis
Pure copper and impure copper electrodes: made from copper from the extraction process
Solution of Cu2+ used
Copperatoms form Cu2+ ions and move from the impurecopper to the pure copperelectrode to become pure coppermetal again
Lots of energy required: expensive
Copper Purification: Displacement
Copperdisplaced from solution using scrapiron as it is cheap and abundant
Coppersulfate + iron = ironsulfate + copper
CuSO4(aq) + Fe(s) = FeSO4(aq) + Cu(s)
Not as efficient as electrolysis
Phytomining:
Plantsgrown on soil containing low grade ores
Plantsabsorbcopper compounds from soil
Plants are burned - the ash contains copper compounds
Copper is extracted from a solution made from the ash by electrolysis
Purecopper is produced
Copper Mining Advantages:
Quicker
Extracts more copper
More economically viable
Disadvantages:
Supply of copper richore is limited
Causes dust and noise pollution
Requires more energy
Destruction of landscapes and habitats
Large amounts of waste rock
Releases more carbon dioxide contributing to global warming
Releases sulfurdioxide causing acidrain
Bioleaching Advantages:
Extractscopper from low grade oils
Conservescopperrich oils
Doesn’t destroylandscape and produces less pollutants
Lower energy costs
Disadvantages:
Slow
Less efficient
Produces toxic waste (not as much as smelting)
Less economicallyviable
Phytomining Advantages:
Extracts copper from low grade ores
Conservescopper richores
Doesn’t destroylandscapes and produces less pollutants
Lower energy costs
Disadvantages:
Produces smaller amount of copper per unit mass
Takes up a lot of space
Growing plants takes tine
Produces carbon dioxide when plantsburn
Land can’t be used to grow food
How should I write a 6 mark question on life cycle assessments?
Extracting and processingraw materials - how much is the local environment being damaged through habitat destruction, use of energy and release of pollutants?
Manufacturing and packaging the product - energy use? release of pollutants? quantity of waste products and ease of their disposal?
Using and reusing the product - how much damage does it do over its lifetime? how long can it be used for?
Disposing of the product - how much space does it take up? how many pollutants are released? how much energy is used?
Final judgement
Limitations of Life Cycle Assessments:
Not easy to quantifyeffects of pollutants as we aren't sure what the total effect will be, so we have to make a value judgement (however we can quantify the use of water, resources, energy and production of waste)
Value judgements are subjective which makes it harder to make a finaljudgement
Some companies use selective/abbreviated LCAs to make their products appear more environmentally friendly in advertising - therefore it is important that they are peer reviewed
Plastic Bags:
Raw materials: Crude oil (not sustainable)
Obtaining raw materials: Lots of energy needed to extract oil
Transporting raw materials: Fuels produce pollution eg. carbon dioxide; possible damage from spillages
Manufacture: Lots of energy needed to separatefractions, cracking and polymerisation
Transporting for use: Fuels produce pollution eg. carbon dioxide
Disposal: Landfill (doesn't rot), incinerator (gives off carbon dioxide), recycling (energy and fuel needed for transport and melting)
Paper Bags:
Raw materials: Trees (can be replanted but deforestation releases carbon dioxide)
Obtaining raw materials: Habitats destroyed when treescut down
Transporting raw materials: Fuels produce pollutants eg. carbon dioxide
Manufacture: Uses lots of water and chemicals eg. bleaches that can harm the environment
Disposal: Landfill (rots giving off methane), incinerator (gives off carbon dioxide), recycling (uses energy and fuel for transport and melting)
hardness
how easily a material can resist being scratched or indented
brittleness
how easily a material breaks when a force is applied
stiffness
how well a material can resist bending
Ceramics:
Materials which are typically hard, brittle, heat-resistant and corrosion-resistant
Made by shaping and firing a non-metallic material at a high temperature
2 main groups: clay ceramics and glass
Clay ceramics eg. china, brick, porcelain are made by shaping wet clay when soft then heating in a high furnace so it hardens - have a high compressive strength
Glass is made by heating a mixture of sand, sodium carbonate and limestone then allowing the molten liquid to solidify - transparent, strong, good thermal insulator
Formulations/Composites:
Made of multiple materials with different properties that have been combined to produce a material with more desirable properties
Usually made from 2 components: the reinforcement (usually long solid fibres or fragments) and the matrix (binds the reinforcementtogether; starts soft then hardens)
Polymers:
Large molecules of high relative molecular mass
Made by linking together large numbers of smaller monomers
Properties dependent on properties of monomers and conditions of reaction
Properties: flexible, easily shaped, good insulators of heat and electricity
Low density vs High density poly(ethene):
Both made from ethene monomers
Low density:
Made in moderate temperatures (100 - 300 °C) with a high pressure (150 MPa) and an oxygen catalyst
More flexible, more transparent, weaker
Used in carrier bags
Polymers are disorganised so intermolecular forces are weaker
High density:
Made in low temperatures (50 °C) with a low pressure (0.1 MPa) and an aluminium oxide catalyst
More rigid but stronger
Used in drainpipes
Polymers are organised so intermolecular forces are stronger
Thermosoftening polymers:
Made from lots of polymer chains
Held together by weak intermolecular forces (no covalent bonds)
Break easily when heated and melt the polymer
Can be remoulded into a different shape
Will harden again when cooled
Thermosetting polymers:
Made from lots of polymer chains
Held together by strong covalent bonds in the form of crosslinksbetweenpolymer chains
Require lots of energy to break so don't soften when heated: have to be burned to break and cannot be remoulded
Hard, strong and rigid
Metals vs Alloys:
Metals: malleable, ductile (not brittle), good conductors of heat and electricity, high melting and boiling points
Alloys: stronger and less malleable
corrosion
the process by which metals are slowly broken down by reacting with substances in their environment eg. rusting