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Using resources (doesn't include practicals will do a paper 2 coggle…
Using resources (doesn't include practicals will do a paper 2 coggle on that later)
Ceramics, composites and polymers
Ceramics
Non-metal solids with high melting points that aren't made from carbon-based compounds
Some can be made from clay - when fired at high temps becomes hard and is ideal for pottery and bricks as it is soft and can be moulded, but then can be hardened
Another example is glass - made by heating mixture of limestone, sand and sodium carbonate until it melts - when cools becomes glass
Borosilicate glass has a higher melting point than soda-lime glass - made in the same way with sand and boron trioxide
Composites
Generally made of two different materials - one material embedded in another
Reinforcement - fibres or fragments of material surrounded by a matrix acting as a binder
Properties of the composite depend on the materials it is made from:
Fibreglass
- fibres of glass embedded in a matrix of polymer (plastic) - low surface density but is very strong. Uses include skis boats and surfboards
Carbon fibre
- also has polymer matrix but reinforcement made up of long chains of carbon atoms bonded together (carbon fibre) or from carbon nanotubes - strong and light so used in aerospace and sports car manufacturing
Concrete
- made from aggregate (sand and gravel)embedded in cement - strong so used in building
Wood
- natural composite made from cellulose fibres held together by an organic polymer matrix
Polymers
Properties of polymer influenced by how its made and what it's made from
For example the properties of poly(ethene) depend on the catalyst that was used and the reaction conditions eg. temp and pressure it was made under
Low density poly(ethene)
is made from ethene at a moderate temperature under a high pressure and with a catalyst - flexible and used for plastic bags and bottles
High density poly(ethene)
- made from ethene at a low temperature and pressure with a different catalyst to LDPE - more rigid and used for water tanks and drainpipes
Thermosoftening polymers
Contain individual polymer chains entwined together with weak forces between the chains - can be melted and remoulded
Thermosetting polymers
Contain monomers that form cross-links between the polymer chains, holding the chains together in a solid structure - don't soften when heated - strong, hard and rigid
Properties of materials
Ceramics
- glass and clay such as porcelain and brick - insulators of heat and electricity, brittle and stiff
Polymers
- insulators of heat and electricity, flexible, easily moulded - many applications including in clothing and insulators in electrical items
Composites
- properties depend on the reinforcement and the binder/matrix used to make them, and have many different uses
Metals
- malleable, good conductors of heat and electricity, ductile (drawn into wires), shiny and stiff - applications include wires, car body work and cutlery
Pure metals are too soft
Alloys
used more often as disrupts structure of metals - making them harder
For example alloys of steel are often used instead of pure iron - made by adding small amounts of carbon and sometimes other metals
Types of steel
Low carbon steel
(0.1-0.3%) - easily shaped - used in car bodies
High carbon steel
(0.22-2.5%) - very strong, inflexible, brittle - bridges
Stainless steel
(chromium added, and sometimes nickel) - corrosion-resistant, hard - cutlery
Everyday life alloys
Bronze
- copper + tin - harder than copper - used to make medals, decorative ornaments and statues
Brass
- copper + zinc - more malleable than bronze and is used in situations where low friction required - such as water taps and door fittings
Gold alloys
- used to make jewellery - pure gold very soft, metals such as zinc, copper and silver used to harden the gold - 24 carat is pure eg. 18 carat is 75% gold
Aluminium alloys
- used to make aircraft - low density is important property in aircraft manufacturing - pure aluminium too soft so alloyed with small amounts of other metals so it is stronger
Corrosion
Corrosion is where metals react with substances in their environment and are gradually destroyed
For iron to corrode it needs to be in contact with both oxygen and water
Rust is hydrated iron(III) oxide
Corrosion only happens on the surface of a material where it's exposed to air
For iron the rust flakes leave the surface, so the iron is continually eroded
Aluminium also corrodes, but isn't completely destroyed as the aluminium oxide that forms when aluminium corrodes forms a protective layer that sticks to the aluminium and stops any further reaction taking place
Ways to prevent rusting
Coat the iron with a barrier to keep out the water and oxygen
Painting/coating with plastic
- ideal for both big and small structures
Electroplating
- uses electrolysis to reduce metal ions onto an iron electrode - metals coated on which don't corrode
Oiling/greasing
- this has to be used when moving parts are involved, eg. bike chains
Sacrificial method
Placing a more reactive metal with the iron, so that metal reacts with the water and oxygen instead of the iron eg. zinc
Galvanising
Uses both methods - the zinc layer is firstly protective, but if it is scratches the zinc around the scratch acts as a sacrificial metal
Finite and renewable resources
Risks of extracting finite resources
Have to balance social, economic and environmental effects of extracting finite resources
Eg. mining metal ores is good as useful products can be made and also provides jobs so brings money into the area, but is bad for the environment as it uses lots of energy, scars the landscape, produces lots of waste and destroys habitats
Some natural resources can be replaced by man-made ones - eg. rubber has been replaced by man-made polymers eg. in tyres
Reuse and recycling
Chemistry is improving sustainability
Approach to development which takes account of needs of present society but doesn't damage lives of future generations
Extracting resources can be unsustainable due to waste produced and energy needed, and processing the materials can be unsustainable as energy used comes from finite resources
People can use less which reduces use of resource and anything needed to produce it
Chemists can develop and adapt processes that use lower amounts of finite resources and reduce damage to the environment eg. developed catalysts that reduce energy required for certain industrial processes
Copper rich ores
Copper is a finite resource and new ways being developed to extract it
Bioleaching
Bacteria are used to convert copper compounds in the ore into soluble copper compounds, separating out the copper from the ore in the process
The leachate (solution produced in the process) contains copper ions which can be extracted eg. by electrolysis or displacement with a more reactive metal eg. scrap iron
Phytomining
Involves growing plants in soil that contains copper
The plants cannot use or get rid of the copper so it builds up in their leaves
Plants can be harvested, dried or burned in a furnace
Ash contains soluble copper compounds which can be extracted by electrolysis or displacement using scrap iron
Recycling metals
Mining and extraction takes lots of energy, most coming from burning of fossil fuels
Recycling metals uses much less energy, conserves amount of metals in the earth and cuts down on waste sent to landfill
Usually recycled by melting them and casting them into the shape of a new product
Depending on what the metal will be used for after recycling, the amount of separation required can change - waste steel and iron can be kept together as they can both be added to iron in a blast furnace to reduce the amount of iron ore required
Recycling glass
Helps sustainability by reducing the amount of energy needed to make new glass products, and also the amount of waste created when glass is thrown away
Glass bottles can often be reused without reshaping
Other forms of glass can't be reused so they're recycled - usually separated by colour and chemical composition
Glass is crushed and melted to be reshaped for uses such as jars or bottles - might be used for different purpose such as insulating glass wool for wall insulation in homes
Life cycle assessments
Looks at every stage of a products life to assess the impact it would have on the environment
Getting the raw materials (1)
Extracting raw materials produces pollution which damages the local environment, and energy needed produces pollution as well
Raw materials often need to be processed to extract the desired materials which often needs more energy - eg. fractional distillation of crude oil
Manufacturing and Packaging (2)
Manufacturing products and packaging can use lots of energy and also causes lots of pollution eg. harmful fumes like CO
Also need to think about any waste products and how to dispose of them - chemical reactions can product waste products - some waste can be turned into useful products which reduces amount which pollutes environment
Using product (3)
Use of product can damage environment eg. burning fuels releases greenhouse gases, fertilisers can flow into streams and rivers and damage ecosystems
How long a product is used for is also a factor - products that use a lot of energy to produce but are used for long time mean less waste in long run
Product disposal (4)
Products often disposed of in landfill sites - takes up space and polluted land and water
Energy needed to transport waste to landfill - pollutants released
Products might be burned which causes air pollution
Plastic vs Paper Bags
Raw materials
Plastic - crude oil
Paper - Timber
Manufacturing and packaging
Plastic - compounds needed to make plastic are extracted from crude oil by fractional distillation, followed by cracking ten polymerisation. Waste is reduced as other fractions have other uses but needs lots of energy
paper - pulped timber is processed using lots of energy and lots of waste is made
Using product
Plastic - can be reused, and used for other things such as shopping eg. bin liners
Paper - usually only used once
Product disposal
Plastic - recyclable but not biodegradable and will take up space in landfill and pollute land
Paper - biodegradable, non-toxic and can be recycled
Problems with life cycle assessments
Use of energy, some natural resources and certain types of waste easily quantified, but effect can be hard to give numerical value to
Not objective method as it takes into account values of the person carrying out assessment - can be biased
Selective LCAs only show some of the impacts of a product on the environment as they can be written to deliberately support the claims of a company - positive advertising
Potable water
Water that's been treated or is naturally safe to drink - essential for life
Not necessarily pure water - pure water only contains H2O molecules while potable water contains other dissolved substances
Important that the levels of dissolved salts aren't too high, and that the pH is between 6.5 and 8.5, and no bacteria are found in the water
How potable water is produced
Depends on where you are
Rainwater is type of fresh water - when it rains water can either collect as surface water or as ground water (in aquifers)
In UK source of water depends on location - surface water tends to dry up first, so in warm areas most of domestic water comes from groundwater stores
Even though it only has low levels of dissolved substances water from fresh sources needs to be treated
Filtration first
- a wire mesh screens out large twigs then gravel and sand beds filter out any other solid bits
Then sterilisation - water is sterilised to kill any harmful bacteria or microbes - done by bubbling chlorine gas through it or by using ozone or ultraviolet light
In some very dry countries not enough ground or surface water, then sea water must be treated by desalination
Distillation can be used to desalinate sea water
Sea water can also be treated by processes that use membranes - by reverse osmosis - salty water passed through a membrane that only allows water molecules to pass through so ions and larger molecules are trapped and separated from the water
Both distillation and reverse osmosis need lots of energy, so are expensive and not practical for producing large quantities of water
Haber Process
Ammonia from hydrogen and nitrogen
Nitrogen is easily obtained from air - air is 78% nitrogen
Hydrogen mainly comes from reacting methane with steam to form hydrogen and carbon dioxide
Reactant gases are passed over an iron catalyst at 450 degrees and pressure of 200 atmospheres
As reaction is reversible some ammonia produced converts back into hydrogen and nitrogen, and it eventually reaches a dynamic equilibrium
Ammonia produced is formed as a gas, but cools in the condenser and liquefies before being removed - unused hydrogen and nitrogen are recycled
Ammonia produced can be used to make ammonium nitrate - a very nitrogen rich fertiliser
NPK fertilisers
Provide plants with essential elements for growth
Used to use manure to fertilise fields
Fertilisers are better as more widely available, easier to use and have just enough of each nutrient so more crops can be grown
Main essential nutrients are nitrogen, phosphorus and potassium - if plants don't get enough of these elements their growth and life processes are affected
These elements may be missing from the soil if they've been used up by the previous crop
Fertilisers replace these missing nutrients or provide more of them - helps to increase crop yield as crops grow bigger and faster - increasing productivity
Contain each element in the right percentage
Ammonia used to produce nitrogen containing compounds
Ammonia can be reacted with oxygen and water in a series of reactions to make nitric acid
Can also react ammonia with acids including nitric acid to get ammonium salts
Ammonia and nitric acid react to produce ammonium nitrate - especially good to use in fertiliser as it has nitrogen from 2 sources
NH3 + HNO3 --> NH4NO3
Carried out in two ways
Industry -
reaction carried out in giant vats at high concentrations resulting in very exothermic reaction.
Heat released used to evaporate water from the mixture to make very concentrated ammonium nitrate product.
In the lab -
reaction carried out on smaller scale using titration and crystallisation.
Reactants at much lower concentration so less heat is produced and safer carry out
After titration mixture needs to be crystallised to give pure ammonium nitrate crystals - not used in industry as it is very slow
Phosphate and potassium
Potassium chloride and potassium sulphate can be mined and used as a source of potassium
Phosphate rock is also mined, but as phosphate salts in rock are insoluble, plants cannot use them as nutrients
Reacting phosphate rock with other acids produces soluble phosphates
Nitric acid - phosphoric acid and calcium nitrate
Sulphuric acid - calcium sulphate and calcium phosphate (single superphosphate)
Phosphoric acid - calcium phosphate (triple superphosphate)