using resources Flashcards
what do humans use the earth’s resources for and where are these produced from
- warmth
- shelter
- food
- transport
in many cases, these resources are produced by agriculture (farming)
what do we do with finite resources from the earth, oceans and atmosphere
we process them to provide energy and materials
what do natural resources supplemented by agriculture provide
- food
- timber
- clothing
- fuels
how does chemistry play an important role in the effective utilisation of our resources - give examples
it improves agricultural and industrial processes to provide new products and in sustainable development
e.g.,
- artificial fertilisers allow us to grow more food with the land available
- provides us with water that is safe to drink
- bioleaching that helps us to extract metals more efficiently
define sustainable development
development that meets the needs of current generations without compromising the ability of future generations to meet their own needs
give an example of a natural product supplemented/replaced by agricultural and synthetic products
natural rubber that originally comes from the sap of a tree, but we can make synthetic rubber using crude oil
define finite resource - give examples
resources that cannot be replaced as quickly as they are being used, meaning they’ll eventually run out e.g., fossil fuels, metals
define renewable resource - give an example
resources that can be replaced as quickly as they are being used, meaning they’ll never run out e.g., wood
what does agriculture do for us? give an example to support
agriculture helps us to use the earth’s resources more efficiently.
- cotton produced from a plant; modern agriculture allows us to grow enough cotton to meet the needs of the world.
define potable water
water that is safe to drink
what is the confusion surrounding potable water
it is NOT pure water in the chemical sense, because it contains a small amount of dissolved substances, unlike pure water which doesn’t contain any
property of drinking water for humans
it should have sufficiently low levels of dissolved salts (e.g., sodium chloride) and low levels of microbes (e.g., bacteria)
what do the methods used to produce potable water depend on
- available supplies of water
- local conditions
how do we get water in the UK
rain provides water with low levels of dissolved substances that collects in the ground and in lakes and rivers
define fresh water
water with low levels of dissolved substances
how is most potable water produced
- an appropriate source of fresh water is chosen
- water is passed through filter beds to remove materials like twigs and leaves
- water is sterilised to kill harmful microbes (chlorine used in the UK)
name 3 sterilising agents used for potable water
- chlorine
- ozone
- ultraviolet light
why do we not need to remove substances in fresh water other than filtering
it already contains low levels of dissolved substances which is the property of potable water, so we don’t need to remove these, unlike waste water which contains organic compounds that need to be broken down
what happens if supplies of fresh water are limited
desalination of salty water or sea water may be required
how do you make salty water or sea water potable
by desalinating the water, either by:
- distillation
- processes that use membranes such as reverse osmosis
what does distillation involve
heating water until it evaporates and then condensing it again - works because salt has a much higher boiling point than water
what does reverse osmosis involve
passing water through partially permeable membranes which only allow water molecules to pass through, leaving the dissolved salts
evaluate the use of the desalination methods
ADVANTAGES:
- they reduce the levels of dissolved minerals
DISADVANTAGES:
- very expensive as they require large amounts of energy
(energy used for heating water in distillation)
(energy used for high pressures in reverse osmosis)
what do urban lifestyles and industrial processes produce large amounts of
waste water that requires treatment before being released into the environment
what do sewage and agricultural waste water require the removal of
- organic matter
- harmful microbes
what may industrial waste water require the removal of
- organic matter
- harmful chemicals
examples of waste water
- sewage waste water
- agricultural waste water
- industrial waste water
steps for treating sewage
- it’s screened by passing it through a wire mesh, removing material like twigs and grit
- undergoes sedimentation where sewage sludge and a liquid effluent are produced
- sewage sludge is taken away and digested by anaerobic bacteria which produce biogas (methane) that can be combusted for electricity. the material remaining after anaerobic digestion can be used as fertilisers for farming
- liquid effluent contains large amounts of organic molecules and harmful microbes that need to be reduced before release into environment. air is bubbled through the effluent, allowing aerobic bacteria to multiply and digest the harmful microbes and break down organic molecules in the presence of oxygen
- effluent can then be safely discharged into the environment (e.g., nearby rivers or the sea)
comment on the relative ease of obtaining potable water from waste water
(not done in the UK)
very hard as it requires lots of steps of treatment and purification. only done in places where water is scarce
comment on the relative ease of obtaining potable water from ground water
the easiest method, as it contains the lowest levels of dissolved substances so takes less stages to treat - once treated with chlorine, it is safe to drink.
however, water from aquifers must be tested carefully for pollution from fertilisers in farms
comment on the relative ease of obtaining potable water from salt water
difficult as it needs to be desalinated which requires a large amount of energy, making it an expensive method
uses of water
- personal hygiene e.g., showers, baths
- flushing toilets
- agriculture
- washing clothes
- drinking
what is happening to copper ores
they’re becoming scarce because they are finite resources, so we have to extract copper from low-grade ores, as there are very few high-grade ores left
how and why do we obtain copper
by mining copper ores - we need it because it is used in electronic equipment due to its ductility
define a metal ore
a rock containing enough metal to make it economical (cost-effective) to extract the metal
what are low-grade ores
rocks containing a very small amount of copper; this means it’s harder to economically extract pure copper from a low-grade ore
methods of extracting copper from low-grade ores
- phytomining
- bioleaching
what do methods of extracting copper from low-grade ores avoid
phytomining and bioleaching avoid traditional mining methods of digging, moving and disposing of large amounts of rock
how does phytomining work
- grow plants on land that contains the desired metal compound
- plant absorbs the metal compound from the low-grade ore
- metal accumulates and concentrates in plant tissue
- plants harvested and burned to produce ash that contains high concentrations of the metal compound
how does bioleaching work
- uses bacteria to extract metal compounds from low-grade ores
- bacteria is mixed with the low-grade ore
- bacteria carry out chemical reactions, producing leachate solutions
- these solutions contain the desired metal compound, which is dissolved in the solution
what happens after bioleaching and phytomining
the metal compounds need to be processed to obtain the pure metal from the compound - we can do this using displacement or electrolysis
evaluate displacement and electrolysis to extract pure metals from their compounds
DISPLACEMENT:
- cheap because uses scrap iron to displace (ADV)
- only works for metals less reactive than iron e.g., copper (DISADV)
ELECTROLYSIS:
- works for metals more reactive than iron (ADV)
- expensive as it uses large amounts of energy (DISADV)
advantages of low-grade ore extraction methods
P&B = Phytomining and bioleaching
- P&B allow us to economically extract metals from low grade ores; important because earth’s resources of metal ores are limited
- don’t involve traditional mining practices like digging, transporting and disposal of large amounts of rock which destroys habitats and requires utilisation of fossil fuels which contribute to climate change
disadvantages of low-grade ore extraction methods
- they take a long time e.g., phytomining takes ages for plants to absorb copper and grow
what does a life cycle assessment (LCA) do
it assesses the environmental impact of products over their life time
state the 4 main stages of LCAs
- extracting and processing raw materials
- manufacturing and packaging
- use and operation during its lifetime
- disposal at the end of its useful life, including transport and distribution at each stage
discuss extracting and processing raw materials (stage 1 of LCAs)
many modern products contain plastics and metals like copper
- plastics made from crude oil undergoes many processes (extraction, transportation, separation, cracking, polymerisation, etc.) to produce plastics.
- all of these processes require large amounts of energy from combustion of fossil fuels; contributes to climate change
- extraction of metals requires large amounts of energy because they must be mined and transported for processing.
- electrolysis and purification of the ore also requires lots of energy and can produce lots of toxic waste products - same with fractional distillation
extracting often also damages local environment, e.g., obtaining wood needed for paper or mining for metals
discuss manufacturing and packaging (stage 2 of LCAs)
- requires large amounts of energy
- may release harmful waste products like pollutants e.g., carbon monoxide or hydrogen chloride
discuss use and operation during its lifetime (stage 3 of LCAs)
for example:
- a battery-powered device will need a large amount of batteries over the course of their life as they have to be replaced often
- producing batteries releases large amounts of waste; environmental concern
- must take into account how long it is used for and how many times it can be re-used
- products that use up lots of energy to produce but can be used for a long time mean less waste and less raw materials needed in the long run
discuss disposal at the end of its useful life (stage 4 of LCAs)
- many products contain harmful chemicals which have to be disposed of; can require a lot of energy
- transportation of used products for disposal to landfill or recycling requires lots of energy
- taking waste to landfill takes up space, pollutes land and water, produces atmospheric pollutants
- non-biodegradable products can take up to a thousand years to degrade
- we can dispose of products using incineration (waste is burnt at very high temperatures); cuts down on waste going to landfill and can be used to generate electricity, but can cause air pollution
describe an LCA for shopping bags made from plastic and paper
STAGE 1:
- paper bags made from wood from trees, plastic bags made from crude oil
- trees are renewable, crude oil is non-renewable and finite
STAGE 2:
- both need to be chemically processed which requires large amounts of energy
- also releases waste products like co2 and harmful chemicals
STAGE 3:
- plastic bags are strong and durable; can be re-used and tend to last a long time
- paper bags tear easily especially when exposed to water; cannot be easily re-used and are usually one-use only
STAGE 4:
- both transported to recyling or landfills
- paper bags more expensive to transport because they have a greater density than plastic bags so are heavier
- plastic is non-biodegradable so cannot be broken down by microorganisms; paper is biodegradable, especially when wet
- plastic bags therefore remain in the environment for a long time, affecting the health of animals and affecting ecosystems, as well as taking space in landfill
why is an LCA not a purely objective (one answer) process
- use of water, resources, energy sources and production of some wastes can be fairly easily quantified
- allocating numerical values to pollutant effects on the environment is less straightforward and requires value judgements, making it subjective to an extent
what are selective/abbreviated LCAs
value judgements or estimates on the effect of pollutants from a product on the environment to evaluate the product. these can sometimes be misused to reach pre-determined conclusions, for example, in support of claims for advertising purposes. this makes them somewhat inaccurate and open to bias
how should LCAs be done
- as a comparison of the impact on the environment of the stages in the life of a product
- should only be quantified where data is readily available for energy sources, water, resources and wastes
what does reducing the use, reuse and recycling of materials by end users do
it reduces (the use of):
- limited resources
- energy sources
- waste
- environmental impacts
what are the main materials humans use in modern life
- metals
- glass
- building materials
- clay ceramics
- most plastics
what is wrong with the main materials we use
- they’re scarce as they come from finite raw materials; puts a strain on the limited resources we have
- obtaining raw materials from the earth by quarrying and mining causes environmental impacts
- lots of energy used to turn raw materials into useful products; comes from combustion of fossil fuels which contributes to global warming
how can we reduce our need for raw materials
by reusing and recycling products
- some products e.g., glass bottles, can be reused so can be crushed and melted to make different glass products
- other products cannot be reused so are recycled for a different use e.g, plastic bottles can be reused as carpets
how do we recycle metals
- melting the metal
- recasting/reforming the metal into different products
what does the amount of separation required for recycling depend on - give an example
- the material
- the properties required of the final product
for example, some scrap steel can be added to iron from a blast furnace to reduce the amount of iron that needs to be extracted from iron ore
environmental impacts of quarrying
- produces large amounts of dust
- destroys habitats
environmental impacts of mining
can release harmful chemicals into environment
what is the issue with recycling metals
they usually need to be separated before being recycled
define corrosion
the destruction of materials by chemical reactions with substances in the environment
example of corrosion and its condition
rusting; both air and water are necessary for iron to rust
it is only rusting when it is talking about the corrosion of iron and alloys of iron like steel; for any other metal, it is simply called corrosion
describe an experiment to show that both air and water are necessary for rusting
three test tubes:
first test tube (water and air) - iron nail in distilled water. test tube is open to the air
second test tube (water) - iron nail in distilled. boiled water. water covered with oil. test tube is open to the air.
- boiling the water removes any dissolved air
- oil prevents any air in the test tube from dissolving in the water
third test tube (air) - iron nail in anhydrous calcium chloride powder. rubber bung on test tube.
- anhydrous calcium chloride powder removes any water from the air in the test tube
- rubber bung prevents any moist air from entering
leave these for several days.
RESULTS:
test tube 1 - iron nail is covered in rust
test tube 2 and 3 - no rust
this tells us that rusting requires both air and water
why is corrosion a problem
because it damages materials
methods for preventing corrosion
- barrier protection
- sacrificial protection
explain how barrier protection works
- a coating is applied that acts as a barrier, e.g., greasing, painting or electroplating
- this protects the material underneath
- aluminium commonly used as it has an oxide coating that protects the metal from further corrosion
explain how sacrificial protection works
- a more reactive metal is used to coat the original metal
- because the coating is more reactive, it will be oxidised instead of the metal we are protecting
- one way to do this is by galvanisation
explain how galvanisation works for iron
- metal is coated with zinc
- this acts as a barrier method to protect the iron underneath from being exposed to air and water
- even if part of the iron is exposed (e.g., some zinc scratches off), there’s still a sacrificial protection because zinc is more reactive than iron
- this means zinc will be oxidised and corrodes instead
what are most of the metals in every day use - describe their properties
alloys - mixtures of a metal and other element(s)
- useful because they are much harder than pure metals
- made by melting down pure metals and mixing in other elements
- distorts regular layers so can’t easily slide over eachother
properties of bronze
- an alloy of copper and tin
- used for statuses because it is hard and tends not to corrode
properties of brass
- an alloy of copper and zinc
- used for musical instruments because it can be formed into different shapes, despite being harder than pure copper
properties of gold
- used as jewellery
- usually an alloy with silver, copper and zinc as pure gold is too soft
proportion of gold in an alloy is measured in carats:
24 carats; 100% pure gold
18 carats; 75% pure gold
etc
properties of steel
- alloys of iron that contain specific amounts of carbon and other metals
- high carbon steel is strong but brittle; used to make cutting tools like chisels
- low carbon steel is softer and more easily shaped; used to make care bodies
what is the problem with normal steel and how is this resolved
- alloy of iron so liable to rust
- to prevent this, we use stainless steel (steels containing chromium and nickel)
- stainless steel is hard and resistant to corrosion
- this makes it useful for cutlery
properties of aluminium alloys
- low in density
- sued in aeroplane bodies
what type of glass is most of the glass we use
soda-lime glass
how is soda-lime glass made
- heating a mixture of sand, sodium carbonate and limestone in a furnace until it melts
- then shaped and cooled
- solidifies into desired shape when it cools
define a ceramic
a non-metallic solid with a high melting point
properties of ceramics
- not made from any carbon-based compounds
- good insulators of heat and electricity
- tend to be stiff and brittle
problem with soda-lime glass
relatively low melting point; this limits its uses
how is borosilicate glass made and how this compares to soda-lime
- melting a mixture of sand and boron trioxide
- melts at higher temperatures than soda-lime glass
uses of the different glasses
soda-lime uses:
- bottles
- drinking glasses
- windows
borosilicate uses:
- for objects that need heating due to higher melting point
e.g.,
- kitchenware
- labware
what can ceramics be made of
- clay (pottery, bricks, etc.)
- glass (soda-lime, borosilicate, etc.)
how are clay ceramics made
- clay is a mineral found in the ground
- wet clay is shaped
- heated in a furnace to harden
what is the difference between glass ceramics and clay ceramics
when producing them, clay is a mineral found in the ground, so you can mine clay naturally, but you can’t just mine glass
how are composites made
by combining two different materials, one embedded in the other
- the reinforcement; fibres or fragments of one material
- the matrix/binder; the other material that surrounds and binds the reinforcement
carbon fibre composite properties
- made up of carbon as the reinforcement and plastic resin as the matrix
- strong and light, making it useful for cars or aircraft parts
reinforced concrete composite properties
- made up of steel bars as the reinforcement and concrete as the matrix
- extremely strong, making it useful for constructing buildings
how can we change the properties of a composite
by changing the matrix and the reinforcement
what do the properties of polymers depend on
- what monomers they are made from
- the conditions under which they are made
how is low density poly(ethene) produced from ethene
polymerise ethene with a high pressure and the presence of oxygen
- moderate temperature
how is high density poly(ethene) produced from ethene
polymerise ethene with a low pressure and a catalyst
- lower temp than LD
how can you change the properties of a polymer
by changing:
- the temperature
- pressure
- catalyst
describe the structure of thermosetting polymers
- strong cross-links between different polymer chains
- these cross-links require large amounts of energy to overcome
- hence they do not melt when heated
describe the structure of thermosoftening polymers
- no cross-links between different polymer chains
- weak intermolecular forces between polymer chains which require very little energy to overcome
- hence they melt when heated
what happens if we cool a melted thermosoftening polymer
we reform the intermolecular forces, so the polymer returns to its solid form
what is the aim of the haber process
to manufacture ammonia which can be used to produce nitrogen-based fertilisers
what are the raw materials for the haber process and where are they extracted from
- nitrogen; from the air
- hydrogen; from natural gas / methane
how is the haber process executed
- purified gases passed over an iron catalyst at 450º and 200atm of pressure
- some hydrogen and nitrogen reacts to form ammonia
- reaction is reversible so some of the ammonia produced breaks down into nitrogen and hydrogen (this is undesired)
how do you separate the ammonia from the hydrogen and nitrogen in the haber process
we cool the mixture which liquefies the ammonia. this makes it easy to remove
what is done with any unreacted hydrogen and nitrogen in the haber process - why is this good
they’re recycled back into the reaction vessel over the iron catalyst - this reduces waste, saves resources and reduces cost
how is the haber process a compromise reaction
PRESSURE:
- increased pressure causes position of equilibrium to shift towards the side with smaller number of molecules
- this is the right hand side (ammonia), meaning yield of ammonia increases
- pressure also increases rate of reaction because there are more reactant particles for a given volume, meaning the frequency of successful collisions increases
- if pressure is too high, it’s expensive, dangerous and can damage equipment, so 200 atmospheres is a compromise pressure
TEMPERATURE:
- high temp is favourable in an endothermic direction, which increases the yield of reactants
- if the temperature is too low, the particles will not have enough kinetic energy meaning there will be fewer successful collisions, decreasing the rate of reaction. also expensive
- a compromise temperature of 450 is used to obtain a relatively fast rate of reaction and a relatively high yield of ammonia
CATALYST:
- iron catalyst increases the rate of reaction by lowering activation energy
- this means more collisions are classed as successful per second, thus increasing the rate of reaction
- DOES NOT affect yield of ammonia or position of equilibrium
what type of reaction is the haber process
- exothermic in the forward direction
- reversible
what would happen if we didnt use a catalyst in the haber process
we would have to increase the temperature even more to get a higher rate of reaction, which would severely affect yield of ammonia
why are fertilisers needed for modern farming
because they contain nutrients and organic compounds necessary for plant growth
what are NPK fertilisers
a group of fertilisers containing compounds of nitrogen, phosphorus and potassium used to improve agricultural productivity, helping plants to grow larger and more rapidly
how are NPK fertilisers produced
they’re produced industrially using a variety of raw materials in several integrated processes to produce the desired fertiliser
what are NPK fertilisers formulations of
various salts
how are NPK fertilisers formulations
they contain the required elements in the proportions and percentages needed by different plants
define a formulation
a mixture of several different substances in carefully measured quantities to ensure the product has the required properties
what can ammonia be used to manufacture
- ammonium salts
- nitric acid
how is nitrogen produced in NPK fertilisers
- main compound of nitrogen in NPK fertilisers is ammonium nitrate
- we use ammonia obtained from haber process to produce nitric acid
- react the nitric acid with more ammonia to make ammonium nitrate in a neutralisation reaction
how is potassium produced in NPK fertilisers
- main compound of potassium in NPK fertilisers is potassium chloride or potassium sulfate
- both are mined directly from the ground without having to undergo any further processing
what is the problem with phosphate rock
it cannot be used directly as a fertiliser because it is insoluble
how is phosphorus produced in NPK fertilisers
- we mine phosphate rock from the ground
- chemically process it for use in fertilisers
- we treat the phosphate rock with nitric acid, sulfuric acid or phosphoric acid
what happens when you treat phosphate rock with nitric acid
- produces phosphoric acid and calcium nitrate
- pH is too low so must neutralise it with ammonia to produce ammonium phosphate that can be used in NPK fertilisers
what happens when you treat phosphate rock with sulfuric acid
- produces a mixture of calcium phosphate and calcium sulfate
- collectively known as single superphosphate which can be used in NPK fertilisers
what happens when you treat phosphate rock with phosphoric acid
- produces calcium phosphate
- known as triple superphosphate
- can be used in NPK fertilisers
comparison of producing fertilisers industrially and in a lab
INDUSTRIAL:
- continuous method (ADV)
- makes much greater quantities (ADV)
- much faster (ADV)
- requires huge quantities of machinery (DISADV)
- more dangerous chemicals (DISADV)
LAB:
- batch method (DISADV)
- makes lower quantities (DISADV)
- much slower (DISADV)
- we use chemicals safer to work with (ADV)
