Using Resources

  • Created by: India.02
  • Created on: 11-06-19 19:21

Ceramics

- They are non-metal solids with high melting points and they aren't made from carbon-based compounds

- Some can be made from clay - a soft material when dug out of the ground, so it can be moulded into different shapes - when it's fired at high temperatures, it hardens to form a clay ceramic - its ability to be moulded when wet and then hardened makes clay ideal for making pottery and bricks

- Another ceramic is glass - it is generally transparent - it can be moulded when hot and brittle when thin

- Most glass is soda-lime glass, which is made by heating a mixture of limestone, sand and sodium carbonate until it melts - when the mixture cools it comes out as glass

- Borosilicate glass has a higher melting point - made using sand and boron trioxide

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Composites

- Made of one material embedded in another - fibres or fragments of a material (reinforcement) are surrounded by a matrix acting as a binder

- Fibreglass - fibres of glass embedded in a matrix made of polymer - low density but very strong - skis, surfboards and boats

- Carbon fibre composites - polymer matrix - reinforcement is either long chains of bonded carbon atoms or carbon nanotubes - strong and light - aerospace and sports car manufacturing

- Concrete - made from aggregate - any material made from fragments, usually sand and gravel - embedded in cement - very strong - building material

- Wood - natural composite of cellulose fibres held together by an organic polymer matrix

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Properties of Polymers

- Properties of polyethene depend on the catalyst used and the reaction conditions

- Low density polyethene - made from ethene at a moderate temperature under a high pressure and with a catalyst - flexible - used for bags and bottles

- High density polyethene - made from ethene but at a lower temperature and pressure with a different catalyst  - more rigid - used for water tanks and drainage pipes

- The monomers that a polymer is made from determine the type of bonds that form between the polymer chains - this determines properties

- Thermosetting polymers - monomers that can form cross-links between the polymer chains, holding the chains together in a solid structure - do not soften when heated - strong, hard and rigid

- Thermosoftening polymers - individual polymer chains entwined together with weak forces between the chains - they can be melted and reshaped

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Different Materials for Different Jobs

- Ceramics - include glass and clay ceramics such as porcelain and bricks - insulators of heat and electricity - brittle and stiff

- Polymers - insulators of heat and electricity - flexible and easily moulded - many applications, including cothing and insulators in electrical items

- Composites - properties depend on the binder and the reinforcement - many different uses

- Metals - generally malleable - good conductors of heat and electricity - ductile (can be drawn into wires), shiny and stiff - many uses, including electrical wires, car bodywork and cutlery

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Alloys

- Regular structure of pure metals makes them soft - salloys are made by adding another element to the metal, which disrputs the structure of the metal, therefore making alloys harder

- Alloys of iron are called steels - often used instead of pure iron - small amounts of carbon and other metals are added to the iron

- Low carbon steel - easily shaped - used for car bodies - High carbon steel - vary hard and inflexible - used for blades (cutting tools) and bridges - Stainless steel - corrosion resistant - used in cutlery and containers for corrosive substances

- Bronze = Copper + Tin - harder than copper - medals, ornaments and statues

- Brass = Copper + Zinc - more malleable - water taps and door fittings (less friction needed)

- Gold alloys - zinc, copper and silver harden pure gold - harder - jewellery

- Aluminium alloys - harder with a low density - aeroplanes

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Corrosion of Iron and Steel

- Corrosion - where metals react with substances in their environment and are gradually destroyed - iron corrodes and rusts easily - it needs to be in contact with both oxygen and water, which present in air, in order to rust

- Corrosion only happens on the usrface of a material, where it is exposed to air

- RUst is a soft crumbly solid that soon flakes off to leave more iron available to rust again - eventually, all the iron in an object corrodes away even if it wasn't at the surface

- Aluminium corrodes when exposed to air - it isn't completely destroyed by corrosion - aluminium oxide that is formed doesn't flake away - it forms a protective layer that sticks to the aluminium and stops any further reactions taking place

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Rusting of Iron

- To show that water alone isn't enough, you can put an iron nail in a boiling tube with just water and the nail won't rust - the water must be boiled to remove oxygen and a layer of oil is needed to prevent air getting in

- To show that oxygen alone isn't enough, you can put an iron nail in a boiling tube with just air and the nail won't rust - calcium chloride can be used to remove any water from the air

- If you put an 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 have bonde to oxygen and water, resulting in a compound that is heavier than the iron

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Preventing Rusting

- Painting/Coating with plastic - ideal for big and small structures - can also 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 - has to be used when moving parts are involved - bike chains

- Sacrificial method - a more reactive metal (zinc or magnesium against iron) is placed with the iron - water and oxygen react with the sacrificial metal instead of the iron

- Galvanisation - spray the metal with a layer of zinc - zinc layer is protective, but if it is scratched, the zinc around the site of the scratch acts as a sacrificial metal

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Improving Sustainability

- Sustainable development is an approach to development that considers the needs of present society while not damaging the lives of future generations

- As well as using non-renewable resources, extracting resources can be unsustainable due to the amount of energy used and waste produced - manufacturing the resources into useful materials is also unsustainable because the energy used often comes from finite resources

- Reducing how much people use of a finite resource means that the resource is liekly to last longer - reducing usage also reduces need to produce them

- Chemists can develop and adapt processes that use lower amounts of finite resources and reduce damage to the environment

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Copper-Rich Ores

- Copper is a finite resource - the supply of copper-rich ores is limited

- Improve sustainability by extracting copper from low-grade ores

- 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 by the process) contains copper ions, which can be extracted by electrolysis or displacement with a more reactive metal

- Phytomining - growing plants in soil that contains copper - plants can use or get rid of copper so it gradually builds up on the leaves - the plants can then be harvested, dried and burned in a furnce - the ash contains soluble copper compounds from which copper can be extracted by electrolysis or displacement

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Recycling

- Mining and extracting requires a lot of energy, most of which comes from burning fossil fuels

- Recycling metals uses less energy, conserves the finite amount of each resource and cuts down the amount of waste getting into landfill

- Metals are recycled by melting them and recasting them into the new shape of the product

- Glass bottles can often be reused without reshaping

- Other forms of glass can't be reused so they are recycled instead - it is separated by colour and chemical composition before being recycled

- It is crushed and melted to be reshaped for use in glass products - it can slo be used for insulating glass wool which is used to insulate homes

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Sewage Treatment

- Sewage is screened - this involves removing any large bits of material as well as any grit

- It is left to stand in a settlement tank and undergoes sedimentation - heavier suspended solids sink to the bottom to produce sludge while the lighter effluent floats on the top

- The effluent in the settlement tank is removed and treated by biological aerobic digestion - when air is pumped through the water to encourage aerobic bacteria to break down any organic matter, including other microbes in the water

- Sludge from the bottom of the tank is removed and transferred into large tanks - it gets broken down by bacteria in anaerobic digestion - this breaks down the organics matter in the sludge - releases methane gas in the process - this can be used as an energy source and the remaining digested watse can be used as a fertiliser

- For waste water containing toxic substances, additional stages of treatment may involve adding chemicals, UV radiation or using membranes

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Haber Process

- The process is used to make ammonia from hydrogen and nitrogen - the reaction is well suited for an industrial scale as the reactants aren't too difficult or expensive to obtain

- Nitrogen is obtained easily from the air (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 a temperature of 450 degrees celcius and at a pressure of 200 atmospheres

- Since the reaction is reversible, some of the ammonia produced converts back into hydrogen and methane again - it eventually reaches dynamic equilibrium

- Ammonia is formed as a gas, but as it cools in the condenser it liquifies and is removed - the unused hydrogen and nitrogen are recycled

- Ammonia produced can then be used to make ammonium nitrate - a nitrogen-rich fertiliser

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Haber Process Compromises

- The forward reaction in the Haber process is exothermic - an increasing temperature will move the equilibrium away from ammonia and towards the nitrogen and hydrogen - this means yield of ammonia would be greater at lower temperatures

- Lower temperatures mean a slower rate of reaction - 450 degrees celcius is a compromise between maximum yield and speed of reaction

- Higher pressures move the position of equilibrium towards the products since there are four molecules of gas for every two molecules of reactants - increasing pressure maximises percentage yield and increases rate of reaction

- Pressure is set a high as possible without making the process too expensive of dangerous to build or maintain

- The iron catalyst speeds up the reaction but doesn't affect yield

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Haber Process Compromises

- The forward reaction in the Haber process is exothermic - an increasing temperature will move the equilibrium away from ammonia and towards the nitrogen and hydrogen - this means yield of ammonia would be greater at lower temperatures

- Lower temperatures mean a slower rate of reaction - 450 degrees celcius is a compromise between maximum yield and speed of reaction

- Higher pressures move the position of equilibrium towards the products since there are four molecules of gas for every two molecules of reactants - increasing pressure maximises percentage yield and increases rate of reaction

- Pressure is set a high as possible without making the process too expensive of dangerous to build or maintain

- The iron catalyst speeds up the reaction but doesn't affect yield

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NPK Fertilisers

- Formulated fertilisrs are better as they are more widely available, easier to use, don't smell and have just enough of each nutrient so more crops can be grown

- Three main elements in fertilisers are nitrogen, phosphorus and potassium - the growth and life processes of a plant are affected when these elements are lacking

- Fertilisers replace these missing elements or provide more of them, which helps to increase crop yield

- NPK fertilisers are formulations containing salts of the three elements, in the right percentages

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Ammonium Nitrate

- Ammonium nitrate can be made by reacting ammonia with nitric acid - nitric acid can be made by reacting ammoina with oxygen and water

- In Industry - reaction is carried out in giatn 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

- In The Lab - reaction carried out by titration and crystallisation - reactants are at a much lower concentration than in industry, so less heat is produced by the reaction and its safer for a person to carry it out - the mixture needs to be crystallised after titration to give pure ammonium nitrate crystals - crystallisation isn't used in industry becuase it is slow

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Phosphate and Potassium

- Potassium chloride and potassium suplhate can be mined and used as a source of potassium

- Phosphate rock is also mined - because phosphate salts in the rock are insoluble, plants can directly absorb them and use them as nutrients

- Reacting phosphate rock with a number of different types of acids produces soluble phosphates

- Reaction with nitric acid acid produces phosphoric acid and calcium nitrate

- Reaction with sulfuric acid produces calcium sulfate and calcium phosphate - known as single superphosphate

- Reaction with phosphoric acid only produces calcium phosphate - known as triple superphosphate

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