Global Challenges Flashcards
What is oxidation and reduction in terms of oxygen?
oxidation = gaining oxygen
reduction = losing oxygen
What is the easiest way to separate a metal from its oxide?
react it with carbon to form the metal and carbon dioxide
What can we not use carbon reduction with all metals?
you can only use it with metals that are less reactive than carbon
What other process separates metals from their oxides other than carbon reduction?
electrolysis`
Why do we find pure gold in the ground, but not pure iron?
gold is too unreactive to react with oxygen in the air, but iron is reactive enough and forms iron oxide
What is corrosion?
the process by which metals are slowly broken down by reacting with substances from their environment
What is the equation for rusting?
iron + oxygen + water —> hydrated iron (lll) oxide
what are the conditions required for rusting to take place?
water, iron and oxygen
What type of reaction is rusting?
redox
how can we investigate the conditions required for iron to rust?
set up 3 test tubes with a bung and an iron nail in each.
The first test tube should have water and no oxygen (water should be boiled to remove oxygen and a layer of oil on top to prevent air dissolving into water)
The second test tube should have just the nail and calcium chloride (to remove any water vapour from the air)
the last test tube should have enough water to keep the nail half wat submerged
Why doesn’t aluminium break down as it corrodes like iron does?
The aluminium oxide forms a protective layer, preventing further oxidation
What are the 2 types of methods we can use to protect iron from rusting?
barrier methods and sacrificial methods
What do barrier methods do?
prevent oxygen and water from touching the iron
What do sacrificial methods do?
a more reactive metal is added to the iron, so that metal reacts instead of the iron
what are 3 main barrier methods?
paint
oil or grease
electroplating
What is electroplating?
using electrolysis to cover the iron with a thin layer of another metal
What is an example of protection that uses both barrier and sacrificial methods?
galvanising
What is galvanising?
coating an object in a thin layer of zinc
What is the Haber process?
the industrial production of ammonia from nitrogen and hydrogen
What is the ammonia used for in the Haber process?
to create nitrogen based fertilisers
How does the Haber process work?
1) input the nitrogen and hydrogen into the reacting vessel
2) Some of the nitrogen and hydrogen react to form ammonia
3) The mixture passes into the condenser and the ammonia cools down to liquid ammonia (it has a low boiling point) whilst the hydrogen and nitrogen stay gaseous
4) the liquid ammonia is collected and the nitrogen and hydrogen are recycled
What are the conditions inside the reacting vessel?
450 C
200 atm
iron catalyst
Why does the Haber process take place at 450 C and 200 atm?
as the reaction exothermic, a lower temp. favours the forward reaction and higher % yield, but to achieve a higher rate of reaction, more temp is needed. 450 C is selected as a compromise. A higher temperature is too expensive as well
Higher pressure will increase rate of reaction and push equilibrium to the right, increasing % yield. High pressure is very expensive and can be dangerous, so 200 atm is a compromise
Is the Haber process an exothermic or endothermic reaction?
exothermic
Which metal acts as a catalyst for the Haber process?
iron
Where do we get the nitrogen required for the Haber process from?
take it from the air
Where do we get the hydrogen required for the Haber process from?
make it from hydrocarbons
What is a fertiliser?
a substance that is applied to soil, in order to supply plants with nutrients.
What is a formulation?
a mixture that has been designed as a useful product. e.g. paint, fertiliser etc.
What does NPK stand for in NPK fertilisers?
nitrogen (N), phosphorous (P), potassium (K)
What are the 3 main elements that plant need from soils?
nitrogen, phosphorous and potassium
What is used to provide nitrogen in the fertilisers?
ammonia made from the Haber process
What is the contact process?
the industrial process which produces sulphuric acid
What are the 3 main steps in the contact process?
1) sulphur is combusted with oxygen to form sulphur dioxide
2) Sulphur is further oxidised using vanadium (V) oxide catalyst to form sulphur trioxide
3) the sulphur trioxide is reacted with water to sulphuric acid
What are the 3 main steps in the contact process using equations?
1) S₈ + 8O₂ → 8SO₂
2) 2SO₂ + O₂ ⇄ 2SO₃
3) SO₃ + H₂O → H₂SO₄
What are the optimal conditions for the contact process?
450 C
2 atm
vanadium (V) oxide catalyst
Which factor increases the rate of reaction but decreases the percentage yield in the contact process?
temperature
What is the purpose of a life cycle assessment (LCA)?
To assess the environmental impact of products
What are the stages of a LCA?
extracting and processing the raw materials
manufacturing and packaging the product
using the product
disposing of the product
What are 3 limitations of LCAs?
Companies can manipulate their LCAs to look more favourable
It is difficult to gather all of the required data about each step
It is difficult to compare different harms e.g. lung disease vs global warming
What are some of the characteristics of ceramics?
hard, brittle, heat-resistant, corrosion-resistant
How are ceramics made?
by shaping and then firing a nonmetallic material, such as clay, at a high temperature.
what are the 2 main groups of ceramics?
clay ceramics and glass.
What are 3 clay ceramics and what is a characteristic they share?
brick, china, porcelain
high compressive strength
What is the most common glass we use?
soda-lime glass
How is soda-lime glass made?
melting a mixture of sand (silicon oxide), sodium carbonate and limestone, then allowing the molten liquid to cool and solidify
How is borosilicate glass made?
by heating sand (silicon oxide) with boron trioxide.
what is a difference in soda-lime glass and borosilicate glass?
borosilicate glass has a much higher melting point
What are composites?
A composite material consists of two or more materials with different properties, that have been combined to produce a material with more desirable properties.
What are the 2 components most composite materials are made from?
the reinforcement (long solid fibres or fragments)
the matrix (binds the reinforcements together, often starts soft then hardens)
What are polymers?
large molecules of high relative molecular mass and are made by linking together large numbers of smaller molecules called monomers.
Generally, what properties do polymers have?
flexible, easily shaped, and good insulators of heat and electricity.
What does LDPE stand for?
low-density poly(ethene)
Which type of poly(ethene) is most flexible, but weakest?
LDPE
What does HDPE stand for?
high-density poly(ethene)
Which type of polymers melt easily when heated?
Thermosoftening polymers
What are the 2 types of polymers?
Thermosoftening polymers
thermosetting polymers
What are general characteristics of metals?
malleable, ductile, good conductors of heat and electricity, and have high melting and boiling points
What is the key difference between metals and alloys?
Alloys are not malleable and much stronger
how does fractional distillation work?
Crude oil is a mixture of hydrocarbons with different boiling points.
The first step is to heat the crude oil to a very high temperature so that all of the compounds are evaporated from liquid to gas.
The hot gaseous hydrocarbons then rise up the fractionating column (because hot gas rises).
As they rise, they cool down, because the top of the column is cooler than the bottom.
The hydrocarbons will condense when they become cooler than their boiling point, and the liquid hydrocarbons then collect in trays and drain out.
The longer chain hydrocarbons condense at the bottom of the fractionating column because they have high boiling points.
Meanwhile the shorter chain hydrocarbons condense at the top of the column because they have much lower boiling points.
What 3 hydrocarbons are used as fuels?
Diesel
Petrol
Kerosene
What is a petrochemical?
a substance made from crude oil via chemical reactions.
what is feedstock?
a raw material used to provide reactants for an industrial reaction.
What are alkanes?
a homologous series of molecules that are hydrocarbons and that only have single bonds
What is the general formula for alkanes?
CnH2n+2
What does a homologous series mean?
group of organic compounds that have similar chemical properties, due to them having the same general formula.
What does saturated and unsaturated mean in terms of molecular bonds?
saturated means that only single bonds are present, but unsaturated means that other bonds are also present (e.g. double bonds)
What is the general formula for alkenes?
CnH2n
What is a fuel cell?
a type of electrochemical cell that converts energy between chemical and electrical
In hydrogen fuel cells, which electrode has what charge?
anode - negative
cathode - positive
What are the electrodes made of in fuel cells?
porous carbon with catalyst
How do hydrogen fuel cells work?
1) Hydrogen comes into the anode compartment and gets oxidised by the anode to become H+ ions
2) the electrons pass around the wire to the cathode, whilst the hydrogen ions pass through the electrolyte to the cathode
3) the hydrogen ions, electrons and oxygen (from the cathode compartment, react together to form water.
4) the water leaves the fuel cell through the outlet
What is the reaction happening at the anode?
H2 —-> 2H+ + 2e-
What is the reaction happening at the cathode?
O2 + 4H + 4e- —–> 2H2O
What is the overall reaction in a fuel cell?
O2 + 2H2 —-> 2H2O
What generates electricity?
the oxidised hydrogen atoms, create a potential difference across the electrodes, driving the electrons through the wire to the cathode
What are 3 pros of hydrogen fuel cells?
only require hydrogen and oxygen (abundant)
dont produce waste
relatively simple
last longer than batteries
less polluting to dispose of
What 4 properties change as a hydrocarbon gets longer?
longer hydrocarbons:
have higher boiling points
are less volatile
are more viscous
are less flammable
What products does complete combustion form?
carbon dioxide + water
What products does incomplete combustion form?
carbon monoxide + (soot) + water
During a combustion reaction, are carbon and hydrogen oxidised or reduced?
oxidised
What functional group do alcohols have?
OH
What is the general formula for alcohols?
Cn H2n+1 OH
What are the 3 main properties of alcohols?
flammable
soluble
can be oxidised to make carboxylic acids
What are some uses of alcohols?
fuels
solvent (they can dissolve things water can’t)
What is the pH of alcohols?
7
What is the functional group of carboxylic acids?
COOH
What does propanoic acid ionise into?
propanoate negative ion and hydrogen positive ion
What are the products when ethanoic acid is ionised?
CH3COO- + H+
ethanoate ion + hydrogen ion
What is ethanoic acid + potassium carbonate?
potassium ethanoate + water + carbon dioxide
How are carboxylic acids made?
by oxidising an alcohol
What does it mean if carboxylic acids are weak acids?
weak acids do not fully ionise in water. This means that weak acids don’t release all their
hydrogen ions.
What is the general formula of carboxylic acids?
Cn H2n+1 COOH
What is addition polymerisation?
adding multiple monomers together to form a long chain polymer
What conditions are needed for addition polymerisation?
high pressure and catalyst
What type of molecules are used in addition polymerisation?
alkenes
What is an ester link?
carbon bonded to 2 oxygens, with one being a double bond. These are created during condensation polymerisation
What are 2 things that reactants must have to undergo condensation polymerisation?
each monomer must have 2 functional groups
there should be 2 different functional groups overall.
Usually a dicarboxylic acid + a diol
What is a dimer?
two monomers combined
Which type of polymers are biodegradeable?
condensation polymers
Why are condensation polymers biodegradable?
Ester links can be broken down by microorganisms
What are 3 naturally occurring polymers?
polypeptide, DNA, Carbohydrates
What are polypeptides made up of and what do they make when folded up?
amino acids, proteins
What is DNA made up of?
nucleotides
What are carbohydrates made up of?
Sugars
What functional groups do amino acids contain?
amino group
carboxylic acid group
an ‘R’ group
what is an amide or peptide bond?
carbon to nitrogen when amino acids join
What are the three elements that make up carbohydrates?
Carbon
Hydrogen
Oxygen
What is cracking?
breaking of longer chain hydrocarbons into shorter chains
What are the 2 types of cracking?
steam and catalytic
How does catalytic cracking work?
the longer chain hydrocarbons are heated and vapourised
the vapour is then passed over hot powdered aluminium oxide (catalyst)
this causes the hydrocarbon to break into smaller hydrocarbons
How does steam cracking work?
The longer chain hydrocarbons are heated and vapourised
the vapour is mixed with steam and heated to very high temperatures
this causes the long chain hydrocarbon to split into smaller ones
What two types of products does cracking create?
shorter alkane and alkene
What type of reaction is cracking?
Thermal decomposition reaction
How do you distinguish between alkanes and alkenes?
if you add alkene to bromine water, it will change colour from orange to colourless
What are the approx. percentages of gases in our atmosphere?
78% nitrogen
20% oxygen
1% argon
0.04% carbon dioxide
What was the earth’s atmosphere like in the first billion years?
very dry
intense volcanic activity
lots of co2 (most), water vapour and nitrogen
some methane and ammonia
What happened to cause carbon dioxide to decrease in atmosphere?
water vapour condensed into water and co2 dissolved into the water
What happened to atmosphere after CO2 dissolved into water?
algae and plants arrived and their photosynthesis decreased amounts of carbon in the air and increased oxygen levels
roughly how old is the Earth?
around 4.6 billion years old
What happened in the water when carbon dioxide dissolved into it?
carbonates were precipitated, creating sediments
What are 3 greenhouse gases?
water vapour
carbon dioxide
methane
what is the greenhouse effect?
solar radiation hits the earth in short wave radiation
some it reflected, some is absorbed and re-emitted
some energy makes it back to space but most is absorbed by greenhouse gases in atmosphere
these molecules re-emit the energy and the process of absorption and emission happens over and over again.
this keeps energy trapped near earth, keeping temps warmer and more stable
what are the 2 main reasons for CO2 increase in atmosphere?
deforestation and burning of fossil fuels
What are the 2 main reasons methane levels are increasing?
farm animals produce methane during digestion
huge amounts of waste may release methane as it decomposes
What are some of the consequences of climate change?
rare weather events (flood, droughts etc.) will become more common and severe
sea level rise
species may not be able to survive in different environment
What are the products of the complete combustion of a hydrocarbon?
water + carbon dioxide
What are the products of the incomplete combustion of hydrocarbons?
carbon monoxide + soot + water
What problems can soot cause?
respiratory problems
global dimming due to smog - more light reflected back into space
What is a problem with carbon monoxide?
Carbon monoxide can bind to red blood cells instead of oxygen and doesn’t unbind meaning less oxygen is able to travel to cells around the body. This can cause fainting, coma, death.
Why is carbon monoxide particularly hard to detect?
it is colourless and odourless
How is sulphur dioxide created?
some hydrocarbons have impurities in them like sulphur, which is oxidised to form sulphur dioxide when hydrocarbons are combusted.
How are nitrogen oxides created?
when nitrogen reacts with oxygen in the air.
But this doesn’t usually happen as it requires very high temperatures.
Where do most nitrogen oxides form and why?
inside internal combustion engines as nitrogen and oxygen need high temperatures to react.
What are the 2 problems with sulphur dioxide and nitrogen oxides?
1) they can cause respiratory problems
2) they can dissolve in clouds to form dilute sulphuric or nitric acid which then galls as acid rain, damaging infrastructure and plants.
What are 3 types of waste water?
domestic
agricultural
industrial
What is domestic waste?
household waste like water from shower, sinks and toilets.
What is agricultural waste?
nutrient run-off from fields and animal waste
What is industrial waste?
waste from factories that make and use chemicals and water
What are the 3 main steps in sewage treatment?
1) screening - removing large objects like plastic and sticks
2) let sewage sit in settlement tank and let sedimentation take place (sludge forms at bottom and effluent forms at top
3) Biological breakdown by microorganisms
What is sludge and effluent?
sludge is heavier solid bits that have sunk to the bottom
effluent is the light part above the sludge
What is the key difference between the effluent and sludge tanks?
sludge is anaerobic
effluent is aerobic
Why is the sludge broken down in anaerobic conditions?
product of breakdown is methane which can be burnt and fertiliser
What happens once both sludge and effluent have been broken down?
sludge products are methane which is burnt and fertiliser which is used/sold
effluent product is clean, safe water which is reused
How are possible toxic substances removed from the waste water?
by adding chemicals or using UV radiation
How is the effluent tank given aerobic conditions and the sludge tank anaerobic conditions?
effluent tank has air pumped into it
sludge tank is sealed
What are 2 ways fuel cells can cause pollution?
1) fossil fuels may be used in manufacturing process
2) catalyst is poisonous so when disposing may pollute environment
