Using Earth's Resources Flashcards
define sustainability
a resource or product being used to meet the needs of the current generation without compromising the ability to meet the needs of future generations to use that resource or product
why can’t we drink natural water found in lakes and rivers etc?
contain harmful microorganisms and salts dissolved from rocks that the water as flowed over and through (these salts need to be at low levels to be safe for humans to drink)
what is water quality that is safe to drink called?
potable water
describe the process of production of potable water in temperate regions
- filter to remove solids
- precipitation reaction to remove harmful dissolved substances (flocculation)
- kill harmful microorganisms (adding Cl2 or O3 or using UV light)
- adjust water pH to neutral if necessary
what are 2 processes of production of potable water in arid regions
- desalination of salt water
- reverse osmosis
what does the desalination of salt water mean?
large scale distillation process (boil seawater) requiring a lot of energy, but is a fast process
how does reverse osmosis produce potable water?
concentration (seawater) through the SPM to an area of very low salt concentration (fresh water). fresh water would then require further processing to enable it to become potable water. low energy but slower process.
What sources can potable water be obtained from? (after treating)
fresh water, sea water, waste water
what is waste water?
water which is produced by domestic and industry and contains harmful bacteria from household sewage and chemicals from industry
what is sewage?
domestic and industrial waste; water contain effluent and sludge
what is effluent?
liquid fraction of sewage
what is sludge?
organic solid fraction of sewage
industrial waste water must have further treatment compared to sewage and agricultural waste water; suggest why
it contains harmful chemicals
what are the stages of waste water treatment??
- screening
- primary sedimentation tanks
- aeration
- final settling tanks
- sludge treatment
- burners
what does screening do in waste water treatment?
removes large solids and grit by filtration
what do primary sedimentation tanks do in waste water treatment?
organic waste (sludge) sinks to the bottom and remaining liquid (effluent) is removed from the top
what does aeration do in waste water treatment?
good bacteria sink to bottom in sludge and treated water is returned to the environment
what does sludge treatment do in waste water treatment?
anaerobic digestion of sludge by bacteria to produce methane and ammonia (used in fertilisers)
what do burners do in waste water treatment?
methane burned for heat and electricity generation
why are metals such useful materials?
good conductors and high MP
what are metals used for?
- cells / batteries
- construction
- cars/ships/planes
- electrical circuits/wires
what is a high grade ore?
a diminishing resource as they are so highly sought because of their relatively high metal content
what is a low grade ore?
contain very small concentrations of metal and would require massive excavations to produce the same amount of metal and would be achieved from a high-grade ore (environmental damage and huge amounts of waste rock)
describe the process of phytomining
- plants and other biomass are grown on top of land under which low-grade ores are situated
- over time the plants absorb metals in the form of minerals from the underlying ores and concentrate the metal within the plant material
- the plants are harvested, burnt, and the ash dissolved to make solutions
- electrolysis or displacement with scrap iron of the solution can then be used to produce the metal
- this method is a slow process as it relies upon the plants growing and concentrating the metal from the low-grade ore
describe the process of bioleaching
- a solution containing a certain type of bacteria is mixed with the low grade ore
- the bacteria react with the low-grade ore and produce a solution containing the metal from low-grade ore - this is a leachate
- the leachate can be used for electrolysis to produce the metal or the metal can be displaced from the leachate using scrap iron
what is corrosion?
the destruction of metals by chemical reaction with chemicals coming from the environment
why is prevention of corrosion key to sustainability of metal resources?
- corroded metals are much weaker than uncorroded metals and will lose many of their properties that make the metal useful in the first place
- this means corroded metals will need replacing which will affect the sustainability of that metal resource
what are 3 methods to prevent corrosion of metals?
barrier method, sacrificial protection, galvanisation
how does the barrier method work?
the coating acts as a barrier between the pure metal and the chemicals in the environment that would otherwise come into contact with the metal and corrode it
what are some examples of the barrier method?
- paint the metal
- cover the metal with oil or grease
- coat the metal with a film of plastic
why don’t aluminium and magnesium corrode?
- they are reactive so the surface reacts with oxygen from the atmosphere
- this produces a metal oxide surface layer to protect the pure metal beneath
how does sacrificial protection work?
- the metal to protect has small pieces of a more reactive metal (sacrificial anodes) joined on its surface
- the more reactive metal will corrode instead of the metal which needs protection
- the sacrificial anodes need replacing as they get used up due to reacting with the corroding chemicals
what are some examples of sacrificial protection?
- zinc or magnesium are attached to the steel hulls of ships and oil rigs to stop the steel structures corroding in the seawater
- magnesium is attached to steel railway lines to stop them corroding
how does galvanising work?
- combines the barrier and sacrificial’s methods of protection
- electrolysis is used to coat the less reactive metal with a more reactive one
- this means that even if the more reactive metal is scratched (barrier) the corrosive chemicals will react with the more reactive metal left instead of the less reactive
what is rusting?
the corrosion of steel or iron
what is the word equation for rusting
iron + water + oxygen ⇒ hydrated iron oxide
what are some features of glass that make it a useful material?
hard, transparent, unreactive, waterproof
what is soda lime glass made from?
silicon dioxide (sand), calcium carbonate, and sodium carbonate
what is borosilicate glass made from?
sodium dioxide (sand) and boron trioxide
what is soda lime glass used for?
windows and bottles - everyday glass
what is borosilicate glass used for?
laboratory and cooking glassware