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What do humans use the Earth’s resources for?
Warmth, shelter, food and transport
What are examples of finite resources?
Crude oil for polymers and fuels
Limestone for cement
Metal ores to extract metals
What is an alternative synthetic product to wool?
Acrylic fibres e.g. polypropene
What is an alternative synthetic product to cotton?
Polyester
What is an alternative synthetic product to silk?
Nylon
What is an alternative synthetic product to wood?
PVC, composites e.g. MDF
What are the requirements for drinking water in the UK?
Low levels of dissolved salts and microbes
What is potable water?
Water that’s safe to drink
Why is potable water not pure in the chemical sense?
It contains dissolved substances
What do the methods used to produce potable water depend on?
Available supplies of water
Local conditions
How is most potable water produced?
Choose an appropriate source of fresh water
Passing the water through filter beds
Sterilising
What are 3 sterilising agents used for potable water?
Chlorine, ozone or ultraviolet light
When would desalination be required?
If supplies of fresh water would be limited and desalination of salty/sea water would be necessary
How can desalination be completed?
By distillation or by membrane-using processes such as reverse osmosis
Why is desalination not desirable?
Uses lots of energy
What needs to be removed from sewage and agricultural waste water so that it can be released into the environment?
Organic matter and harmful microbes
What needs to be removed from industrial waste water so that it can be released into the environment?
Organic matter and harmful chemicals
What happens during sewage treatment?
screening and grit removal
sedimentation to produce sewage sludge and effluent
anaerobic digestion of sewage sludge
aerobic biological treatment of effluent
What are some traditional methods for mining metal ores?
Digging, moving and disposing of large amounts of rock
What happens during phytomining?
Plants absorb metal compounds
Plants are harvested and burnt
Ash contains metal compounds
What happens during bioleaching?
Bacteria feed on low-grade metal ores
The leachate is obtained from waste copper ore and contains the metal compounds
What is a low grade ore?
An ore that contains a small percentage of the metal or its compound
How can copper be obtained from solutions of copper compounds?
By displacement using scrap iron or by electrolysis
What does an LCA (life cycle assessment) carry out?
An assessment into the environmental impact of products at these stages:
extracting and processing raw materials
manufacturing and packaging
use and operation during its lifetime
disposal at the end of its useful life, including transport and distribution at each stage
Why can selective or abbreviated LCAs be misused?
Misused to reach pre-determined conclusions e.g. in support of claims for advertising purposes
What does the reduction in use, reuse and recycling of materials by end users reduce?
Use of limited resources
Use of energy sources
Waste
Environmental impacts
What are some example of items produced from limited raw materials?
Metals
Glass
Building materials
Clay ceramics
Most plastics
What does quarrying and mining cause?
Environmental impacts as a result of obtaining raw materials
How can glass bottles be reused?
Crushed and melted to make different glass products
How can metal be recycled?
By melting, recasting or reforming into different products
What does the amount of separation required for recycling depend on?
The material and the properties required of the final product
What is corrosion? Give an example.
The destruction of materials by chemical reactions with substances in the environment. E.g. rust
What is necessary for iron to rust?
Air and water
How can corrosion be prevented?
By applying a coating that acts as a barrier:
greasing
painting
electroplating
What prevents aluminium from corroding?
An oxide coating
What is sacrificial protection?
Where some coating are reactive and contain a more reactive metal to provide sacrificial protection e.g. zinc galvanises iron
What is bronze an alloy of?
Copper and tin
What is brass an alloy of?
Copper and zinc
What is gold used in jewellery an alloy of?
Silver, copper and zinc
How many carats is 100% gold?
24
What are steels?
Alloys of iron that contain specific amounts of carbon and other metals
What are the properties of high carbon steel?
Strong but brittle
What are the properties of low carbon steel?
Softer and more easily shaped
What do stainless steels contain?
Chromium and nickel
How is soda-lime glass made?
By heating sand, sodium carbonate and limestone
What is borosilicate glass made from? What are its properties?
Made from sand and boron trioxide, Melts at higher temperatures than soda-lime
How are clay ceramics, pottery and bricks made?
By shaping wet clay and heating it in a furnace
What do the properties of polymers depend on?
The monomers they’re made from and the conditions under which they’re made
What happens to thermosoftening polymers when they’re heated? Why?
They melt because they’re intermolecular forces are weak
What happens to thermosetting polymers when they’re heated? Why?
They don’t melt because of their cross-linking
What are most composites made up of?
A matrix or binder surrounding and binding together fibres of the other material, the reinforcement
What are some examples of composites?
Plywood
Concrete
Fibreglass
What is the Haber process used for?
Used to manufacture ammonia which can be used to produce nitrogen-based fertilisers
What are the raw materials for the Haber process?
Nitrogen from the air and hydrogen from natural gas
What happens during the Haber process?
Purified gases are passed over an iron catalyst at a high temperature (450°C) and a high pressure (200 atm)
Reaction is reversible of ammonia is formed and broken down
On cooling, the ammonia liquefies and is removed
What is the equation for the Haber process?
nitrogen + hydrogen → ← ammonia
Why is a higher pressure not used during the Haber process?
It would produce higher yields but it would be too expensive to run
Why is a higher temperature not used during the Haber process?
Lower temperatures would increase the yield but it would be produced too slowly
What are NPK fertilisers made up of?
Nitrogen, phosphorus and potassium
What are NPK fertilisers?
Formulations of various salts containing appropriate percentages of the elements
What can ammonia be used to manufacture?
Ammonium salts and nitric acid
What is phosphate rock treated with to produce soluble salts that can be used as fertilisers?
Nitric or sulphuric acid
What salt is produced when phosphate rock is treated with nitric acid?
Phosphoric acid and calcium nitrate
What salt is produced when phosphate rock is treated with sulphuric acid?
Single superphosphate, a mixture of calcium phosphate and calcium sulfate
What salt is produced when phosphate rock is treated with phosphoric acid?
Triple superphosphate (calcium phosphate)
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