C10: Resources Flashcards
(29 cards)
Define ‘Finite’
Means they cannot be replaced as quickly as fast as they are being used eg. fossil fuels.
Define ‘renewable’
We can replace them as quickly as we use them, so they will never run out.
Define ‘sustainable’
We are meeting the needs of today, without preventing future generations from meeting theirs.
What does drinking water have to be? (2)
- Have low levels of dissolved salts, such as sodium chloride.
- Cannot have high levels of microbes such as bacteria
What is potable water?
Water that is safe to drink, but it does contain a small amount of dissolved substances
What is pure water?
Water with no dissolved substances
Describe the steps needed to produce potable water: (from fresh water)
- Chose a freshwater source eg. a river
- Pass the water through filter beds to remove solids eg. leaves and suspended particles
- Sterilse the water to kill microbes. Use chlorine, ozone or ultra-violet light.
What does desalination do?
Reduces the amount of dissolved minerals in the water
Describe ways of desalinating the water: (2)
- Distillation
- Reverse osmosis
What is the problem with desalination techniques?
- Both processes require lots of energy, which make them very expensive.
Why must waste water be treated before it is released back into the environment?
- Contains a large amount of organic molecules eg. urine and faeces
- Also contains harmful microorganisms such as bacteria
Describe how waste water is treated:
- Sewage is screened by passing through a mesh, this removes solids.
- The sewage settles in large sedimentation tanks. This produces a liquid effluent and a semi-solid sludge which sinks.
- The sludge is taken away and digested by anaerobic bacteria. This produces biogas which can be burned for electricity. Then the sludge can be used as a fertilizer for farming.
- The liquid effluent is still full of harmful organic molecules and microorganisms, which need to be reduced. Air is bubbled through the effluent. Aerobic bacteria multiply, and they digest the harmful stuff.
- The liquid effluent can be safely discharged.
What special stage is used to treat water from industry?
Harmful chemicals need to be removed first. After this it is treated normally.
Evaluate which water sources are easiest to make safe to drink.
- Aquifers: can usually be drank after being sterilized. However, must be carefully checked as it could be contaminated eg. from farms.
- Sewage: takes many purification steps, so only done where water is scarce.
- Salt water: needs to be desalinated. Requires lots of energy and is expensive.
Give one use of copper
In electrical equipment such as phones.
Why are alternative methods of extracting copper needed?
Copper ore is becoming scarce, which means we need to extract copper from low-grade ores.
What is a low grade copper ore?
Copper ore which only contains a small amount of copper.
Describe phytomining
- Plants are grown on land containing the metal compound that we want.
- The plants absorb the metal compound as concentrate it in their tissue
- The plants are then harvested and burned, which produces ash with a relatively high concentration of the metal compound.
Describe bioleeching
- Bacteria are mixed with the low grade ore
- They carry out chemical reactions to produce a solution called a leachate, which contains the metal compound we want.
Describe the extraction process (after bioleeching/phytomining)
We can use a displacement reaction (eg. with iron), or extract it using electrolysis.
What is the positives of bioleeching and phytomining?
- Allows us to economically extract copper from low grade ores, which is important as the Earth’s resources are limited.
- They don’t involve digging, transporting or disposing of large amounts of rock like traditional mining.
What does a life cycle assessment do?
Attempts to put a number on the environmental impact of a product.
What are the four main stages of a lifecycle assessment?
- The environmental impact of extracting and processing raw materials eg. plastics and metals
- Manufacturing, packaging and transporting
- Environmental impact of the product during it’s lifetime.
- Disposal at the end of it’s useful life.
Life cycle assessment for a paper bag / plastic bag:
Paper: Wood from trees. Renewable. Destructive to habitats such as forests. Requires lots of water. Not strong, used only once. Are heavier so take more energy to transport. Biodegradable
Plastic: Crude oil. Nonrenewable. Extracting it can be harmful, eg. if there is an oil leak. Strong and can be reused. Lighter so take less energy to transport. Plastic is non-biodegradable, so a major form of litter.
Both need to be chemically processed which creates a large amount of waste products and uses a large amount of energy.
