The Earth's resources - C14
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What is a finite resource
They are resources which are being used up quicker than they can be replaced
Examples of finite resources
Coal, crude oil and natural gas
What is an infinite resource
They are resources which are being replaced at the same rate as they are being used
Examples of infinite resources
crops used to make biofuels
what are the uses for water
solvent and a coolant
What is potable water
Water that is fit to drink
How is water made fit to drink
It is made fit by passing it through filter beds to remove solids and adding chlorine, ozone or by passing ultra-violet light through it to remove microbes
how can water be purified
Distillation or desalination
What is desalination
It is reverse osmosis which uses membranes to separate dissolved salts from salty water
What is the disadvantage of desalination
Lots of energy is required to achieve a high pressure
What is the disadvantage of distillation
It requires lots of energy
What happens to waste water
It is treated at a sewage works before being released into the environment
What are the steps to treating waste water
• Screening • Primary treatment • Secondary treatment • Final treatment
What is the screening step
It is the removal of large solids and grit
What is the primary treatment step
The solids in the water are collected as sludge and the liquid goes to the next tank
What is the secondary treatment step
Useful bacteria feed on organic matter and harmful microorganisms in aerobic conditions
What is the final treatment step
The useful bacteria form a sediment at the bottom of the tank and either sent back into the secondary treatment tank or into where the sludge is kept The water is now safe to discharge back into the environment but if the environment is sensitive the water can be run through a bed of sand
What happens to the sludge
It is separated and broken down by anaerobic digestion and dried It can be used as a fertiliser or a renewable source
How is copper extracted
Smelting or adding it to sulfuric acid and then using it as an electrolyte or being displaced by scrap iron whilst in solution
What is smelting
When the metal is made impure using air and high temperatures and is then used as the positive electrode is electrolysis
What methods are used on low grade copper ores
bioleaching or phytomining
What is phytomining
It is when plants absorb the metal ore and then are burnt and the metal is extracted from compounds in the ash
What is bioleaching
It is when bacteria feed on the ores and produce a solution of metal ions which can be displaced by something and then used in electrolysis to make the pure metal
What are LCA’s
They are assessments carried out to assess the environmental impacts of products or services