Materials - Unit 2 Topic 7 Flashcards
What is the definition of natural materials?
Materials derived directly from natural materials.
What is the definition of synthetic materials?
Materials made when raw materials are put through a manufacturing process to make a synthetic material.
Gold, limestone, polythene, linen, rubber, copper, wood, Kevlar, aluminium, granite, polyester, Pyrex.
Which of these are natural and which are synthetic?
Natural - Gold, limestone, linen, wood, copper, aluminium, granite.
Synthetic - Polythene, rubber, Kevlar, polyester, Pyrex.
What manufactured materials can you obtain from rock?
Aluminium from bauxite
Glass from sand, limestone + sodium carbonate
Ceramics from sand + clay
Lime from limestone
What manufactured materials can you obtain from crude oil?
Fuels, plastics + detergents
What manufactured materials can you obtain from air?
Nitrogen + oxygen
What manufactured materials can you obtain from sea water?
Salt, iodine, hydrogen + sodium hydroxide.
What manufactured materials can you obtain from plants?
Fuels from biomass, cotton + medicines.
What is nanotechnology?
Relatively new science that is the study of atoms and molecules.
What does nanometre mean?
10-9m
What size of particles does nanotechnology refer to?
1 - 10nm in size
What is the difference between nanoparticles and larger particles?
Larger surface area to volume ratio.
What are gold nanoparticles used for?
Catalysts to convert CO to CO2
Give 3 properties of silver nanoparticles?
Antibacterial, antiviral and antifungal.
Used to sterilise hospital equipment.
Give 2 uses for nanotubes.
Mini electronic devices and smaller, faster computers.
How are nanoparticles used as coatings?
Thin layers of scratch resistant polymer can be used to protect lenses of glasses, contacts and cameras. Layers of polymer can also be used to make fabric stain resistant.
What are the conflicting reports about nanomaterials?
Some reports say they are harmless but others claim they may damage human cells.
Why would the ‘Take Back’ policy ensure nanomaterials would not affect the environment?
The policy would ensure that no nanmaterials would end up in waste and therefore that they would not affect the environment.
What is the health concern with carbon nanotubes?
The nanotubes can behave like asbestos when inhaled.
Why do engineers say that carbon nanotubes are safe?
Engineers claim that the nanotubes cannot be inhaled as they would be bound up in electrical products.
What are the two most common ways of extracting a metal from its ore?
Chemical reduction using carbon or carbon monoxide.
Electrolysis
Why do metals higher than carbon in the reactivity series have to be extracted using electrolysis?
Metals high in the reactivity series are very reactive and need a powerful method to extract them.
Metals below carbon in the reactivity series can be extracted by reduction using carbon. How does it work?
Carbon can take the oxygen away from the metals which are less reactive than the carbon itself is.
Method of extraction for: Potassium Sodium Calcium Magnesium Aluminium
Electrolysis Electrolysis Electrolysis Electrolysis Electrolysis
Method of extraction for: Zinc Iron Lead Copper Silver Gold
Heat with carbon/carbon monoxide Heat with carbon/carbon monoxide Heat with carbon/carbon monoxide Roasting in air Occur naturally Occur naturally
What is electrolysis?
When an electrical current passes through a liquid that causes a chemical reaction. The reaction is a breakdown of the substance into simpler substances.
What is an electrolyte?
An ionic compound that has been melted or dissolved in water.
What is a cathode?
The electrode attached to the negative pole.
What is an anode?
The electrode attached to the positive pole.
What is a cation?
Positive ion
What is an anion?
Negative ion
What is an electrode?
Metal strips or graphite rods placed into the liquid and connected to a supply of electricity.
What happens to the anions at the anode?
They lose electrons and become neutral atoms.
What happens to the cations at the cathode?
They gain electrons and become neutral atoms.
Why are the electrodes made of graphite?
It is a good conductor of electricity and unreactive.
Label diagram of electrolysis of a molten electrolyte.
Page 6
Why does the electrolysis of lead bromide need to be carried out in a fume cupboard?
It produces a harmful gas which must be contained.
What product is formed at the cathode during the electrolysis of lead bromide?
Silver bead of lead
What product is formed at the anode during the electrolysis of lead bromide?
Brown bromine fumes
Why can’t lead bromine conduct electricity when solid?
Ions can’t move.
What product is formed at the cathode during the electrolysis of lithium chloride?
Silver grey liquid lithium.
What product is formed at the anode during the electrolysis of lithium chloride?
Yellow-green chlorine gas
In the electrolysis of molten lead bromide, name a piece of apparatus that can be connected in the circuit to show that an electric current is flowing through the electrolyte.
Light bulb
What is the name of aluminium’s ore?
Bauxite
What is added to pure aluminium oxide before it is electrolysed?
Molten Cryolite
At what temperature is the electrolysis of aluminium carried out?
900c
State 2 purposes of cryolite.
Lowers the melting temperature of bauxite
Increases conductivity
How is molten aluminium removed from the cell in the electrolysis of aluminium?
Tapped off
Why is the electrolysis of aluminium from its ore more expensive than the extraction of iron from its ore?
Electricity is expensive
Why does the anode have to be replaced during the electrolytic extraction of aluminium?
Oxygen at anode reacts with carbon electrode at high temperature which produces CO2 gas and wears it away.
Label diagram of the electrolysis of aluminium from its ore.
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Where should an aluminium extraction plant be sited?
Near cheap source of electricity such as hydroelectric power station, good transportation links, good water supply, waste disposal facilities, skilled workforce nearby + not close to any areas of natural beauty or conservation areas.
What percentage of aluminium cans are recycled?
What percentage of energy does recycling aluminium use compared to electrolysis of bauxite?
Is it cheap or expensive?
26%
5%
Most cost effective material to recycle.
What are 3 negative effects of mining on the local environment?
Noise pollution , dust pollution + destroying natural habitats.
State 3 uses for aluminium?
Drink cans, aircraft bodies + door frames.
Label diagram of the blast furnace.
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Name an ore from which iron can be extracted.
Haematite
What are the stages of extracting iron from the blast furnace?
Hot oxygen blown into base of furnace + coke burns to heat it to 1500c forming CO2 which reacts with more coke to from CO. CO reduces FeO to Fe. Limestone added which thermally decomposes to CaO which combines with sandy impurities (silicon dioxide) to form slag (calcium silicate) which floats on top. Hot waste gases heat air pumped into bottom of furnace. Carbon (pig iron) is turned into steel by lowering carbon content and adding other metals.
What are the waste gases formed when extracting iron from the blast furnace?
Nitrogen, CO + CO2.
What is slag used for?
Making roads, landfill + foundations for buildings.
In what ways does the manufacture of iron help the economy?
Provides jobs, cheap + produces exports.
What environmental problems arise with iron manufacture?
Polluting air, noise pollution, destroying natural habitats + unsightly slag heaps.
What raw materials are used in the extraction of iron ore?
Limestone, coke, hot air + iron ore.
What is the main purpose of adding limestone to the blast furnace when extracting iron?
Removing acidic impurities.
What are the disadvantages of recycling?
Sorting recycled materials is labour intensive and expensive.
What are the advantages of recycling?
Less mining, less energy use, less pollution, less natural habitat destruction, fewer eyesores + saves resources.
What are the disadvantages of incinerating/landfill?
Toxic gases released, wastes land, ash residue toxic + needs specialised landfill needed, incineration prevents landfill + more transport of waste to incineration sites than to landfill.
What are the advantages of incinerating/landfill?
Heat energy harnessed to generate electricity.
What are the disadvantages of production of new materials?
More mining, more raw materials used, more energy used, more pollution, more destruction of habitats + more eyesores created.
What are the advantages of production of raw materials?
Workforce skilled in industrial processing.
Where is bauxite imported from?
NW Africa, Central America, Jamaica + Australia.
What properties of aluminium make it useful to the electrical industry?
Good conductor + low density.
What percentage of carbon is found in cast iron produced by the blast furnace?
What change occurs to amount of carbon when converted to steel + why?
4%
Reduced to 1% as removing carbon makes it less brittle.
