RESOURCESSSS
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what do humans use the earths resources for
warmth, shelter, food, transport
how are most of earths resources made
agriculture
what are trees used for
timber and fuel
how is synthetic rubber produced
using crude oil
where does natural rubber come from
the sap of a tree
what does it mean when a resource is finite
they cant be replaced as quickly as theyre being used, theyll eventually run out
examples of finite resources
• metal • fossil fuels
examples of renewable resources
wood
what does renewable mean
we can replace these resources as quickly as we use them, so theyll never run out
what does it mean when human activities are SUSTAINABLE
• we can meet our needs without preventing future generations to meet theirs
examples of how chemistry plays an important role in how we use resources
• Artificial fertilisers allow us to grow more food with the land available • provides us with water safe to drink • processes such as phytomining and bioleching help us extract metals more efficiently
what does water have to contain to make it safe enough for humans to drink
• low levels of dissolved salts such as sodium chloride • low levels of microbes such as bacteria
what is potable water
water that is safe to drink
what is the difference between pure water and potable water
pure water contains no dissolved substances at all and has a ph of 7, whilst potable water contains dissolved substances, but in quite small amounts
where does most potable water come from in the UK and why
rainwater, it contains low levels of dissolved substances - rain collects in the ground in aquifers and in lakes, rivers and reservoirs and all of these are good sources of fresh water
how to produce potable water
• First choose a good source of fresh water, eg a river • Pass the water through filter beds to remove all leaves and suspended particles • Sterilise the water with chlorine, UV light or ozone to kill microbes
how is potable water produced in countries where the water is either to salty to drink
desalination
what does desalination do
it reduces the levels of dissolved minerals down to an acceptable level for potable water
how to carry out desalination
using distillation - pass the water through membranes, reverse osmosis
disadvantages of desalination
require very large amounts of energy which makes them expensive
examples of what humans use water for
• hygiene like baths and showers • flushing toilets • washing clothes • agriculture
what does waste water contain
• a very large amount of organic molecules (eg from urine and faeces) • harmful microorganisms such as bacteria
How is waste water treated step by step
• The sewage us screened by passing through a mesh, this removes solids and pieces of grit • the sewage settles in large sedimentation tanks • The sludge is taken away and digested by anaerobic bacteria 4.air is bubbled through the liquid effluent • After this stage, the liquid effluent can be safely discharged into nearby rivers or seas
why is the sewage passed through a mesh
removes solids and grit from the water