RESOURCESSSS Flashcards
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
why does the sewage settle in large sedimentation tanks
this produces a liquid effluent and a semi solid sludge which sinks
why is the bacteria used in waste water treatment useful
in the absence of oxygen, these bacteria can produce biogas which can be burned for electricity
what can digested sludge be used for
fertilisers and farming
why is air bubbled through the liquid effluent
The liquid effluent contains large amounts of organic molecules and harmful microorganisms, so bubbling air through it allows aerobic bacteria to multiply
why are the aerobic bacteria useful
in the presence of oxygen, the aerobic bacteria digest the organic molecules and harmful microorganisms
what is the easiest way to produce potable water
using ground water from aquifiers, this is safe to drink once it has been treated with chlorine
- however, they can be polluted with fertilisers from farms
where are most metals found
in the Earths crust, already reacted with other elements
uses of copper
- used in electronic equipment such as phones
what does a metal ore contain
it contains enough metal to make it economical to extract the metal
what foes economical mean
cost effective
problems with extracting copper from its ore
they are becoming scarce(running out)
what are low grade ores
ores that contain a small amount if the metal, meaning they are harder to extract economically
how does phytomining work
- Plants are grown on the land containing the metal compound we want
- The plants absorb the metal compound and they concentrate it in their tissue
- The plants are then harvested and burned
- The ash contains a relatively high concentration of the metal compound
how does bioleaching work
- Bacteria are mixed with the low grade ore
- The bacteria carry out chemical reactions and they produce a solution called a leachate
- The leachate contains the metal compound we want
4.
How to extract a metal from its COMPOUND (not ore)
- if it is a low reactivity metal, we can use a displacement reaction
- using electrolysis
why are bioleaching and phytotyming useful
- they allow us to economically extract metals from low grade ores, which is important as the Earth’s resources of metal ores are limited
- ## these methods dont involve digging, transporting, and disposal of large amount of rock like traditional mining
carry out a life cycle assessment on a plastic bag vs paper bag
EXTRACTION/ RAW MATERIALS - produced using chemicals from crude oil(non renewable)
- produced from wood from trees(renewable)
- both need to be chemically processed, which requires a large amount of energy and releases waste products
- plastic bags are strong, can be reused
- paper bags weak and can rip easily
- both plastic and paper bags have to be transported
-paper bags heavier than plastic, takes more energy to transport - plastic is non biodegradable, so major form of litter, fill up landfills
- paper breaks down quickly when whet
what are some issues with life cycle assesments
- we cannot be certain of how damaging some waste products are to the environment
- this means in some cases we have to make estimates or value judgements which may not always be accurate
- LCAS can be biased eg to support claims by advertisers
what are the stages of LCAs
- Raw materials and extraction
- Manufacture
- Transportation
- Use
- Disposal
examples of materials that humans produce
plastic
glass
metal
clay ceramics
how are raw materials often obtained
by quarrying and mining
- takes a lot of energy to turn these raw materials into useful products
disadvantages of quarrying
produces large amounts of dust
destroys habitats
disadvantages of mining
can release harmful chemicals into the environment
why is recycling and reusing important
they help save limited resources and energy
- will reduce the amount of waste that we produce, will have a less harmful effect on the environment
how can glass bottles be reused
they can be crushed and melted to make different glass products
how can metals be recycled
be melting and recasting or reforming into different products
problems with recycling metals
- they usually need to he separated before being recycled, but this depends on the properties of the final product
how to reduce the amount of iron that we need to extract from iron ore
- some scrap steel can he added to iron from a blast furnace
- this reduces the amount of iron that we need to extract from iron ore
what is corrosion
the destruction of materials by chemical reactions with substances in the environment
examples of corrosion
rusting
what materials does rusting occur on
iron and alloys of iron
how to investigate the conditions required for rusting
- Fill three test tubes and put an iron nail in each, one filled with with distilled water, one filled with boiled distilled water and covered in oil, and the last filled with ANHYDROUS calcium chloride powder with a rubber bung on the test tube
- leave these for several days and look for changes
why is the water covered in oil in the corrosion experiment
to prevent any air in the test tube from dissolving in the water
what does anhydrous calcium chloride do
removes any water from the air in the test tube
what dos a rubber bung do
prevents any moist air from entering
what will the results of the corrosion experiment be
- in the first test tube, the iron is covered in rust
- in the other test tubes, there is no rust
- this tells us rusting requires both air and oxygen
how to stop corrosion
- grease or paint the material
- coat the material with metal (electroplating)
- galvanising (coating metal with zinc)
why does galvanising prevent corrosion
- the layer of zinc acts as a barrier against air and water. this prevents the iron from corroding
- if the zinc gets scratched, it still prevents corrosion since zinc is more reactive than iron, but the zinc corrodes rather than the iron
what is sacrificial protection
using a more reactive metal layer on top of a less reactive one
what is an alloy
a mixture which contains a metal blended with other elements
how are alloys made
by melting our metal, mixing in other elements, and then allowing the alloy to cool
why are alloys harder than pure metals
- since the atoms in a metal form layers, if we hammer the pure metal, its layers will slide over each other
- the atoms in an alloy are different sizes and this disrupts the layers and stops them from sliding
features of bronze
- it is an alloy of copper and tin
- used for statues as it is extremely hard and tends not to corrode
features of brass
- is an alloy of copper and zinc
- harder than pure copper, but can be formed into different shapes
- can be used for musical instruments or door handles
how is gold made harder
by being alloyed with silver copper and zinc
what is 24 carat
100% pure gold
what is 18 carat
75% pure gold
features of steel
- steels are alloys of iron, containing specific amounts of carbon
features of high carbon steel
- extremely hard
- brittle
- tends to break if we hit it with a hammer
- used to make cutting tools such as chisels
features of low carbon steel
- softer than HCS
- more easily shaped
- used to make car bodies
why can steel rust
because its an alloy of IRON
how to prevent the rusting of steel
use stainless steels, which contain chromium and nickel, which are resistant to corrosion
features of aluminium alloys
- they are low density
- used in aeroplane bodies
what is the most used type of glass
soda lime glass
uses of soda lime glass and how to make it
- used in windows and bottles
- to make soda lime glass, mix sand, sodium carbonate and limestone
- heat this into a furnace until it melts
- when it cools, it solidifies into any shape we want
features of borosilicate glass
- higher melting point than soda lime
- this makes the glass more useful for objects which require heating such as kitchenware and labware
how is borosilicate glass made
- melting sand and boron trioxide
how are clay ceramics made
- by shaping wet clay then heating them in a furnace
what is clay
a mineral we find in the ground
what are composites
a combination of two or more materials to improve properties
how are composites made
from two materials, a matrix and a binder surrounding and binding together fibres or fragments of the other material, which is called reinforcement
examples of composite materials
- carbon fibre composite (carbon as the reinforcement material and plastic resin as the matrix) - strong an light so used in cars or aircraft parts
- reinforced concrete - strong and used to make buildigs
how is a polymer formed
by joining together a large number of monomers
what do the properties of polymers depend on
- the monomer
- the conditions used to make the polymer
features of low density polyethene
- soft
properties of high density polyethene
- harder
how could we change the properties of a polymer
- change temperature
- change pressure
- change reaction catalyst
properties of thermosoftening polymers
- they melt when heated
- we can reshape them while they are soft
- they go back to a solid when we cool them down
what happens if we heat then cool a thermosoftening polymer (structure wise)
- Thermosoftening polymers are held together by intermolecular forces
- If we heat the polymer, the intermolecular forces break, now the polymer strands can separate from each other and the polymer melts
2. If we cool the melted polymer, we reform the intermolecular forces, and the polymer goes back to solid
properties of thermoSETTING polymers
- they do not melt when heated
- polymers are connected to each other by strong crosslinks
why dont thermosetting polymers heat when melted
- the string crosslinks are not broken by heat
uses of ammonia
nitrogen based fertilisers
how is ammonia produced
using the Haber process, purified nitrogen and hydrogen are passed over an iron catalyst at around 450 degrees celsius and 200 atmospheres pressure, and this causes some of the hydrogen and nitrogen to react to form ammonia
- as its a reversible reaction, some of the ammonia breaks back down into nitrogen and hydrogen
equation for the Haber process
N2+3H2 —> 2NH3
how can nitrogen be extracted
from the air
how is hydrogen produced for the Haber process
by reacting methane with steam
how to increase the yield of ammonia
- cool the ammonia to turn it into a liquid which is removed
- recycle the unreacted nitrogen and hydrogen back over the catalyst
in the Haber process, which reaction is EXOTHERMIC?
the forward reaction, meaning a relatively cool temperature will shift the equilibrium to the right hand side
why can the rate of reaction and equilibrium never be constant in the haver process
- equilibrium will shift to the right if temperature is too low for example
- a cooler tenperature will make the reaction slow
- so there is a trade off between the rate of reaction and equilibrium
why do we use a temperature of 450 degrees in the Haber process
- its a compromise temperature as we get a relatively fast rate and a relatively high yield of ammonia
- high temperatures require more energy and this costs more
why can we not go higher than 200 atmosphere pressure with the Haber process
- very high pressures are expensive and dangerous
why are fertilisers critical for modern farming
they replace the elements which have been taken up by plants
what do NPK fertilisers contain why are these useful
- nitrogen
- phosphorus
- potassium
- compounds containing these elements improve agricultural productivity and they help plants grow larger and more rapidly
what are NPK fertilisers
formulations of various salts containing appropriate percentages of the elements
what is the main compound of nitrogen in NPK fertilisers and how is it made
ammonium nitrate(NH4NO3)
- made by using ammonia made through the Haber process, we can use this ammonia to produce nitric acid
- we then react the nitric acid with more ammonia to make ammonium nitrate
how is the potassium in NPK fertilisers produced
- comes from the salts potassium chloride and potassium sulfate
- both these compounds are mined from the ground and can be used directly without any further processing
how is the phosphorus in NPK fertilisers produced (nitric acid)
- treating phosphate rock with nitric acid produces phosphoric acid and calcium nitrate
- phosphoric acid contains phosphorus, but we cannot add this directly to plants, so we neutralise it with ammonia
- this produces ammonium phosphate which can be used in NPK fertilisers
how is the phosphate in NPK fertilisers produced (sulfuric acid)
- if we treat phosphate rock with sulfuric acid, we make a mixture of calcium phosphate and calcium sulfate
- this mixture is called a single superphosphate and this can be used in NPK fertilisers
what happens if we treat phosphate rock with phosphoric acid
we make a triple superphosphate and these can be found in NPK fertlisers
compare the industrial production of fertilisers with the laboratory preparations
- for example, ammonium nitrate is made by mixing ammonia with nitric acid and this is a neutralisation reaction
- in the school lab, we would use dilute solutions of ammonia and nitric acid to make them safe to work with
- in industry, the ammonia is used as gas and the nitric acid is concentrated. this is much more dangerous as the reaction is very exothermic, meaning the heat had to be safely removed and used for later stages
- in the school lab, we produce crystals by using a water bath and bunsen burner which requires a lot of heat energy
- in the industry, some of the energy for evaporation is provided by the exothermic reaction from earlier
- in the school lab, we can only produce a small amount of ammonium nitrate in one go, this is called a batch process
- in industry, the chemical is produced by a continuous process, meaning that thousands of kilograms can be produced easily
what does a life cycle assessment attempt to do
put a number in the environmental impact of a product
what does boiling the distilled water do
removes any dissolved air
how does aluminium protect itself from corrosion
the surface of aluminium naturally reacts with oxygen in the air to form a. thin layer of aluminium oxide which protects the metal beneath from further corrosion
disadvantages of soda lime glass
low boiling point limits its uses
examples of clay ceramics
pottery
bricks
how are clay ceramics made
- when it’s wet, clay can be shaped
- it’s then heated in a furnace to harden
