C14 The Earth's Resources
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what are the Earth’s resources used for?
food shelter transport warmth
in most cases, how are the resources that humans use produced?
agriculture
what can trees be used for?
timber fuel
what does finite mean?
a resource that cannot be replaced as quickly as it is being used
what are some finite resources?
metals fossil fuels
what does renewable mean?
a resource that can be replaced as quickly as it is used
what does potable water mean?
water that is safe to drink it is low in microbes and sufficiently low levels of dissolved salts
what is pure water?
it contains just water molecules there are no dissolved substances
how is potable water produced?
• choose a source of fresh water • pass water through filter beds • the water is then sterilised to kill microbes
what can be used to sterilised water?
• chlorine • ozone • UV light
what is desalination?
a process which reduces the levels of dissolved minerals to an acceptable level for potable water
how is desalination carried out?
• distilation • reverse osmosis
why is desalination expensive?
both processes (distilation and reverse osmosis) require a lot of energy
what is water used for?
• drinking • personal hygiene • agriculture • flushing toilets • washing clothes
why does waste water have to be treated before going back into the environment?
it contains a large amount of organic molecules as well as harmful microbes
what are the stages of waste water treatment?
• water is screened through a mesh to remove solids • sewage settles in sedimentation tanks which produces an effluent and sludge • sludge is digested by anaerobic bacteria • air is bubbled through the liquid effluent to allow aerobic bacteria to multiply • aerobic bacteria digest organic molecules and harmful microbes • liquid effluent is then safely discharged into rivers or the sea
what is produced in the anaerobic digestion of sludge?
biogas that is burned for electricity
what can digested sewage sludge be used for?
fertilisers for farming
what needs to be removed from water waste from industry?
harmful chemicals
what is the easiest way to produce potable water?
to use ground water from aquifers treated with chlorine
how is potable water produced when water is scarce?
directly from waste water which takes many purification steps
what does salt water need to become potable water?
it needs to be desalinated
why is copper an important metal?
it is used in electrical equipment
why do we have to extract copper from low grade ores?
the high grade copper ores are running out