C6 Flashcards
what is a metal ore?
a rock which contains enough metal to make it economical to extract the metal
how can a metal be extracted from it’s ore?
by reduction (using carbon) or by electrolysis (splitting with electricity)
what do some ores may have to be before metal is extracted?
concentrated- getting rid of unwanted rocky material
what are two other ways to extract metals from their ores?
-biological methods
-displacement reactions
when an ore is reduced what happens?
oxygen in removed from it
how does the position of the metal in the reactivity series effect reduction?
it determines whether it can be reduced with carbon
metals higher than carbon in the reactivity series…
can be extracted using electrolysis
metals below carbon in the reactivity series
can be extracted by reduction using carbon
what is the reactivity series order?
potassium
sodium
calcium
magnesium
aluminium
carbon
zinc
iron
tin
lead
hydrogen
copper
silver
gold
platinum
what is reduction?
removal of oxygen from a compound
what is displacement?
a reaction where a more reactive metal removes a less reactive metal from it’s compound
what state does a metal have to be in before it is extracted using electrolysis?
it has to be molten
what is the main difference in electrolysis and reduction with carbon?
electrolysis is expensive as it uses electricity
what is smelting?
an ore being heated in a furnace
what are two pure unreactive metals?
silver and gold
why is it better to extract copper using electrolysis?
smelting produces copper which is impure- it won’t conduct electricity.
copper is often used in electrical wiring- which makes it not useful.
electrolysis is used to purify it even if it is expensive.
what are low grade ores?
ores that only contain a small amount of metal in them
what are two biological methods of extraction?
bioleaching
phytoextraction
what is bioleaching?
use of bacteria to separate metals from their ores. the bacteria get energy from the bonds between the atoms in the ore which separate the metal from the ore.
what is phytoextraction?
growing plants in soil that contains metal compounds. the plants cant use or get rid of the metals so they gradually build up in the leaves. the plants are then harvested, dried and burned in a furnace
the only problem with this is that plants take a while to grow
what is a life cycle assessment?
an assessment that looks at each stage of the life of a product- it shows the potential environmental impact at each stage
what is in a life cycle assessment?
-use of sustainable raw materials
-use of energy at all stages
-use of water at all stages
-production and disposal
what could you consider when choosing raw materials?
-metals have to be mined and extracted from their ores- needs lots of energy which causes pollution
-raw materials for chemical manufacture often come from crude oil:
- finite resource
- getting crude oil and refining requires a lot of energy and causes pollution
what should you consider when assessing manufacture of a product?
-use of energy
-pollution (harmful gases)
-waste products and how to dispose of them
-use of water in chemical manufacture and water pollution
what can some waste be turned into?
other useful chemicals which reduces the amount that ends up polluting the environment
what can you consider when assessing product use?
-if gives off toxic fumes
-fertilisers can leak into water sources and cause damage to eco systems
-burning fuels releases greenhouse gases
what should you consider when assessing disposal of a product?
-landfill waste can pollute water and land and products in landfill may be burnt which causes air pollution
what does burning fossil fuels cause?
acid range and climate change
why is recycling a good option?
-recycled materials use little energy needed to extract and refine the material
-it saves money
-recycling cuts down on waste sent to landfill- decreases pollution
why might recycling be complex?
-you need energy to reprocess the materials into new forms
-items will often need sorting into different catagories
-you need to compare how much energy is used for recycling vs disposing
what is crude oil formed from?
buried remains of plants and animals
what is a hydrocarbon?
a compound that contains carbon and hydrogen only
what is viscosity?
how thick a substance is
what is flamability?
ability to ignite something
what is crude oil mostly used for?
used as a raw material to create lots of petrochemicals- petrol or natural gas
what is crude oil a mixture of?
lots of different length hydrocarbons
how are the different compounds in crude oil separated?
by fractional distillation
what is the process of fractional distillation using crude oil?
-crude oil is heated until most of it has turned into a gas
-the gas enters the fractionating column
-the hydrocarbons at the bottom have a high boiling point and they turn back into liquids and drain out the collumn at the bottom
-the shorter hydrocarbons at the top of the column have lower boiling points and they turn into a liquid and drain out at the top of the column where it is cooler.
where is it hot and where is it cold in a fractionating column?
cold at the top
hot at the bottom
short hydrocarbon top
long hydrocarbons bottom
what is the order of the hydrocarbons in a fractionating column from top to bottom?
-LPG (liquefied petroleum gas)
-petrol
-naptha
-kerosene
-diesel
-oil
what is petrol used for?
cars
what is naptha used for?
used in chemical production
what is kerosene used for?
airplane jet fuel
what is diesel used for?
diesel engines
what is bitumen used for?
ships and lubricating oil
what are the bonds between hydrocarbon molecules called?
strong covalent bonds
what are the bonds between different hydrocarbon molecules in crude oil called?
intermolecular forces
what happens when crude oil is heated?
the molecules gain kinetic energy and they might gain enough energy to overcome the intermolecular forces
why don’t covalent bonds break between hydrocarbons?
the bonds are much stronger than intermolecular forces
why do intermolecular forces break more easily in small molecules?
the forces are stronger between big molecules
what does crude oil provide energy for?
generating electricity
heating homes
transport
provides raw materials needed for chemicals (plastics)
what is cracking?
splitting up long chain hydrocarbons
what does cracking do?
turns long chains of alkane (hydrocarbon) molecules into smaller alkane (hydrocarbon) molecules
what does cracking need?
-catalyst to speed up the reaction (alluminium oxide)
-large amounts of heat to break the strong covalent bonds between alkanes (hydrocarbons) (400 degrees to 700 degrees)
-large amounts of pressue (70atm)
what does cracking produce lots of?
alkane molecules which can be used to make polymers (plastics)
what did volcanoes release into the atmosphere?
carbon dioxide, steam, methane, ammonia
what is different about an alkane and alkene?
alkenes have a double bond
alkanes have a single bond
what are large molecules of alkanes broken down into?
alkanes and alkenes
what are the advantages of phytoextraction?
-requires less energy than smelting
-produces less air pollution
-reduces the amount of waste rock
what are the disadvantages of phytoextraction?
-can produce toxic chemicals
-much slower process
-electrolysis requires large amounts of energy
what are the advantages of bioleaching?
-simple process
-cheap process
-can use it on low grade ores
-environmentally friendly and fewer waste gases produced
what are the disadvantages of bioleaching?
-slow process
-toxic chemicals are produced
-has low efficiency
what did the world’s atmosphere start off with?
carbon dioxide
water vapour
hydrogen
sulfur dioxide
how was nitrogen put in our atmosphere?
formed by ammonia reacting with oxygen
released by dentrifying bacteria
how was oxygen put in our atmosphere?
through photosynthesis in plants
how much nitrogen is in our atmosphere currently?
78%
how much oxygen is in our atmosphere currently?
21%
how does human activity effect the atmosphere?
-human population increasing- more respiration- more carbon dioxide released
-greater demand for electricity in lighting, cooking, heating, transport
-energy consumption from burning fossil fuels releases carbon dioxide
-deforestation
what is the effect of greenhouse gases?
-causes the average temperature of the earth to increase
-can cause flooding due to polar ice caps melting
-severe weather changes
-extinction
what can we do to prevent fossil fuel emissions?
-limit our use of fossil fuels
-walking or cycling instead of driving
-turning your central heating down
-encourage the public industry to become more energy efficient
what are two alternative fuels to fossil fuels?
ethanol
biodesel
what is biofuel produced from?
vegetable oils (rapeseed and soybean oil)
what can you mix with biofuel?
ordinary diesel fuel which can be used to run a diesel engine
what are the advantages of biofuel?
-carbon neutral
-engines don’t need to be converted
-produces less sulfur dioxide and other pollutants than regular diesel or petrol
what are the disadvantages of biofuel?
-we can’t make enough to replace diesel
-expensive to make
-increases food prices
what is acid rain caused by?
sulfur dioxide and oxides of nitrogen
when they mix with clouds they form dilute sulfuric acid and nitric acid which falls as acid rain
what are the main causes of acid rain?
power stations
internal combustion engines
what are the effects of acid rain?
-causes lakes to become acidic
-kills plants and animals
-kills trees
-damages limestone buildings and stone statues
-causes metal to corrode
where does sulfur come from?
sulfur impurities in fossil fuels
how are nitrogen oxides created?
from a reaction between nitrogen and oxygen in the air
ignore
ignore
what is photochemical smog?
a type of air pollution
what is the dangerous aspect of carbon monoxide?
it can stop your blood carrying oxygen around your body- causes fainting, comas and death
how is carbon monoxide formed?
when carbon compounds are burnt without enough oxygen- incomplete combustion
how is particulate carbon formed?
when small pieces of solids (mainly carbon) , particulates during incomplete combustion are released into the atmopshere.
what is soot?
carbon particulates which have fallen back to the ground and deposited as black dust
what are the negative aspects of carbon particulates?
they reduce air quality, and can cause or worsen respiratory problems
where do we get our water from?
lakes
rivers
reservoirs
aquifers (rocks that trap water underground)
what are the three main fossil fuels and where do they come from?
water vapour- combustion
carbon dioxide- fossil fuels
methane- decomposing rubbish and animal waste
explain the greenhouse effect:
-sun emits short wavelength radiation (UV light) which warms the earth
-the earth loses heat my emitting long wave radiation back to space
-the greenhouse gases in the earth’s atmosphere absorb some of the long wavelength radiation
-the greenhouse gases re-radiate this thermal radiation in all directions to earth. this warms the atmosphere
how can we reduce the amount of carbon dioxide in the air?
use less fossil fuels and electricity
how can we reduce the amount of carbon monoxide, particulate carbon and nitrogen oxides in the air?
using catalytic converters, burning less fossil fuels, driving less
what is potable water?
water that is filtered and safe to drink- has no impurities in it
what are the steps to getting potable water?
- coagulation
- sedimentation
3.filtration - chloronation
what is coagulation?
adding alluminium sulfate into water which causes clay, dirt and organic matter to clump together to form floc. due to gravity the floc settles at the bottom of the water tank. this makes it easier to remove the waste by filtration and sedimentation.
what is sedimentation?
large tanks allow floc to settle at the bottom of the tanks as sludge. then dripping water into tanks allows extra oxygen to mix with the water which provides oxygen for microbal respiration.
why is water dripped in a tank in sedimentation?
it allows extra oxygen to mix with the water which provides oxygen for microbal respiration
what is filtration?
the water moves through a layer of charcoal and coal before being filtered again using sand. Sand acts as a microfilter which traps air which increases oxygen for microbal respiration- this helps decomposition.
what is chloronation?
disinfecting water by adding chlorine gas- prevents disease
fluroine is also added with strengths teeth and prevents tooth decay
why is chloronation so beneficial?
it is easy, inexpensive and reliable
why are some people against fluranation?
-people think it might cause cancer and tooth flekking
what is cryolite?
a compound added into alluminium oxide to lower it’s melting/boiling point
what are the electrodes in alluminium oxide electrolysis made of?
graphite
why do the electrodes need to be replaced in alluminium oxide electrolysis?
because the oxygen molecules produced at the anode will react with the graphite electrodes which will form carbon dioxide gas
what do you put in and get out in alluminium oxide electrolysis?
in- alluminium oxide moxed with cryolite
out- molten pure alluminium
why is electrolysis so expensive?
- melting compounds like alluminium oxide requires a large amount of energy which costs money
- a lot of energy is required for the electric current
what is made at the cathode in alluminium oxide electrolysis?
alluminium
Al 3+ + 3e - ——- Al
reduction
what is made at the anode in alluminium oxide electrolysis?
2o2- 4e- ——- o2
oxidation
what are alkanes?
hydrocarbons with single bonds only
C2H2n+2
the elements and their carbon amounts:
1- methane
2- ethane
3-propane
4-butane
why are shorter hydrocarbons more useful?
-it improves the supply of fuel- helps match demand
-(alkenes- shorter hydrocarbons) can be used to make polymers and other chemical products
