Topic 8/9 - Fuels and Earth Science / Separate Chemistry Flashcards
What is crude oil?
Complex mixture of lots of different hydrocarbons
Main source of hydrocarbons and is used as a raw material to create lots of useful substances in the petrochemical industry
Can be seperated into fractions - simpler hydrocarbons
Where is crude oil sourced from
Underground, formed over millions of years from dead plant and animal matter. Its non-renewable (finite) resource.
What are hydrocarbons?
Compounds which just contain hydrogen and carbon.
How are the hydrocarbons found in crude oil arranged?
Chain or rings and are mostly alkenes ( CnH2n+2)
How are the fractions in crude oil separated?
Fractional Distillation
Crude Oil
How does fractional distillation work?
Oil is heated untill most of it has turned into gas. The gases enter a fractioning column ( the liquid bit, bitmuten, is drained off at the bottom)
In the column theres a temperature gradient ( hot at bottom and cooler as you go up)
How does fractional distillation seperate the crude oil hydrocarbons?
The longer hydrocarbons have higher boiling points, they turn back into liquids and drain out of the column early on, when they’re near the bottom.
The short hydrocarbons have lower boiling points, they drain much later on.
What is the order of hydrocarbons in fractional distillation?
Top - cooler - shorter chains
Gases
Petrol
Kerosene ( Parrafin )
Diesel Oil
Fuel oil - about 40
Bitmuten - 70+ hydrocarbon chains
Bottom - hotter - longer chains
these are examples of non-renewable resources like methane (natural gas)
What is bitmuten used for?
To surface roads and roofs
What is fuel oil used for?
Fuel for large ships and power stations
What is diesel oil used for?
Some
What is kerosene used for?
Used as fuel in aircraft
What is petrol used for?
Fuel in cars
What are gases used for?
Domestic heating and cooking
What is a homologous series, how do neighbouring compounds differ within it?
A family of molecules which have the same general formula and share similar chemical properties
The molecular formulas of neighbouring compounds differ by a CH2 unit
What are the 2 main types of homoglous series?
Alkanes and Alkenes
How do intermolecular forces vary in hydrocarbons?
The intermolecular forces of attraction break more easily in small molecules than they do in bigger molecules - forces are stronger in bigger molecules
Big molecules have higher boiling points as a result
Why are shorter hydrocarbons easier to ignite?
they have lower boiling points, and tend to be gases at room temperature.
These gas molecules mix with oxygen in the air to produce a gas mixture which bursts into flames if it comes in contact with a spark
Why are longer hydrocarbons harder to ignite?
They are usually liquids at rooms temperature. They have higher boiling points and are much harder to ignite
What is viscosity a mesure of?
how easily a substance flows
How does viscosity vary through hydrocarbons?
The stronger the force is between hydrocarbon molecules, the harder it is for liquid to flow.
Fractions with longer hydrocarbons = higher viscosity = Thick (treacle)
What happens when you burn hydrocarbons in oxygen?
Combustion reactions - why theyre good fuels as its very exothermic
What is complete combustion and its products?
Hydrocarbons burning in plenty of Oxygen
Only products are Carbon Dioxide and Water
Hydrocarbon + Oxygen -> Carbon Dioxide + Water
What is incomplete combustion?
Hydrocarbons burning in a limited supply of Oxygen
What does incomplete combustion produce as well as carbon dioxide and water?
Carbon monoxide(g) (CO) and carbon in the form of soot
less oxygen is produced than carbon
How can carbon monoxide damage the body?
it can comine with red blood cells and stop blood from doing its proper job of carrying oxygen around the body - Lack of oxygen supply to the brain = fainting, coma, death
How can incomplete combustion damage the environment?
During incomplete combustion, tiny particles of carbon can be released into the atmosphere, when they fall back to the ground they form soot.
Soot makes buildings look dirty, reduces air quality, and can cause or worsen respitory problems
How does burning fossil fuels cause acid rain?
When fossil fuels burn, they release mostly CO2
They also release other harmful gases such as sulfur dioxide and various nitrogen oxides.
Sulfur dioxide comes from impurities in fossil fuels. when it mixes with the clouds, it forms dilute sulfuric acid. Then it falls as acid rain
How does acid rain damage things?
- Causes lakes to become acidic and plants/animals die as a result
- Kills trees, damages limestone buildings, and stone statues can also cause metal corrode
How does nitrogen oxide damage things?
Created from a reaction of nitrogen and oxygen in the air, caused by energy released in combustion reactions.
Contribute to acid rain and photochemical smog - air pollution that can cause breathing difficulties
What are the pros of hydrogen gas?
Energy
Very clean fuel
In a hydrogen fuel cell, hydrogen comines with oxygen to produce energy, only waste product is water. Hydrogen is obtained from water - renewable rescourse
What are the cons of hydrogen gas?
Energy
You need a special, expensive engine.
Expensive and often uses energy from another source
Hard to store
What is cracking?
Splitting up long chain hydrocarbons
- turns longer saturated ( alkane ) molecules into smaller unsaturated (alkene)
- Form of thermal decomposition
- the longer molecules produced from fractional distillation are cracked into smaller ones because theres more demand for smaller ones like petrol and diesel
- Also produces alkene molecules, which can be used to make polymers
Thermal decomposition
When one substance breaks down into at least two new ones when you heat it - breaking strong covalent bonds, so you need lots of energy - catalysts are often used
how does cracking work?
Vaporised hydrocarbons are passed over a powdered catalyst at about 400 C - 700 C and 70 atm
Aluminium oxide is the catalyst used. The longer molecules break up or “crack” on the surface of the catalyst used.
How do you test for Oxygen?
Re-lit glowing splint
What are alkanes ?
Saturated hydrocarbons
Formula : CnH2n + 2
H
I
H-C-H
I
H
(Add middle column each time)
Methane
What are the first 4 alkanes?
Methane - CH4
Ethane - C2H6
Propane - C3H8
Butane - C4H10
Why are alkanes saturated and alkenes unsaturated?
Alkanes have a double bond, making them unsaturated as they are able to make more bonds
What are alkenes?
C=C double bond
Unsaturated
Formula - CnH2n
H H
C=C
H. H (add HCH each time)
What are the first 3 alkenes?
Ethene, Propene, Butane
What happens to hydrocarbons in combustion reactions?
they are oxidised
What is the test for alkanes / alkenes?
Bromide water
alkene will turn orange bromide water clear, as its double bond reacts with the bromine
Alkane has no spare bonds.
What are addition polymers made from?
Unsaturated monomers, these can open up their double bonds and join together to form polymer chains.
What are polymers
Substances of high average relative molecular mass made by joining up lots of small repeating units called monomers. The monomers make addition polymers that have a double covalent bond
What is a functional group?
A group of atoms that determine how a molecule reacts (the same in molecules of same homologous series)
What is the functional group of alkEnes?
C=C
What are the products of complete combustion with alka/enes
Carbon Dioxide and Water
Ethene into a polymer equations
Ethene -> Poly(ethene)
Pressure and Catalyst
C2H4 -> (C2H4)n
What are nanoparticles
Really tiny particles, 1-100 nanometres across
they have different properties from the bulk chemical its made from - fullerenes are different from lumps of carbon
How many atoms do nanoparticles roughly have?
a few hundred atoms, so bigger than atoms and simple molecules but smaller than pretty much everything else
What is an example of nanoparticles?
Fullerenes - they contain nanotubes
the covalent bonds make it carbon nanotubes very strong
Why do nanoparticles have a high surface area to volume ratio?
As particles decease in size, the size of their surface area increases in relation to their volume
so SA:V ratio increases
How does a nanoparticles high SA:V ratio affect them?
High SA:V ratio compared to bigger particles
-> Gives them different properties, because a much greater proportion of their atoms are avaliable to interact with substances they come into contact with.
What is nanoscience
Usng nanoparticles
What new uses of Nanoparticles being developed?
Catalysts
Cosmetics
Nanomedicine
Lubricant coatings
Electic chips
Sports equipment
Surgical masks and wound dressings
How are Nanoparticles being used as catalysts?
Huge SA:V ratio, so they can make good catalsysts
SA increase = FreQ Collisions increase = increase RofR
How are Nanoparticles being used for new cosmetics?
New cosmetics e.g. sunscreens, have been made using nanoparticles.
The small particles provide better protection but dont leave white marks on skin
How are Nanoparticles being used as Nanomedicine?
The idea for nanomedicine is that tiny fullerenes are absorbed more easily by the body than most particles. This means they could deliver drugs right into the cells where its needed.
How are Nanoparticles being used as lubricant coatings?
New lubricants using fullerenes e.g. artificial joints and gears
How are Nanoparticles being used in electricals?
Nanoparticles conduct electricity, so they can be used in tiny electric circuits for computer chips
How are Nanoparticles being used for sports equipment?
Nanoplastics are added to plastics in sports equipment. e.g. tennies rackets, golf clubs and golf balls.
They make plastic much stronger and more durable, without adding much mass
How are Nanoparticles being used in medical equipment?
Silver nanoparticles are added to the polymer fibres to make surgical masks and wound bandages. This gives the fibres antibacterial properties
How are the the effects of nanoparticles on health not fully understood?
- the way they effect the body isnt undestood - important new products are fully tested
- Some are worried we are using nanoparticles before the effects on human bodys are fully discovered
- e.g. they may not be able o break down properly, causing a build up in cells.
What is the word equation for cracking?
Long-chain hydrocarbon molecule (alkAne) -> Shorter Alkane + Alkene
What was phase 1 of the atmosphere?
1) The Earth’s surface was originally molten for millions of years - almost no atmosphere
2) Then it cooled and formed a thin crust, but volcanoes kept erupting, releasing gases from inside the Earth - The “Degassing” released mainly Carbon Dioxide, but also steam methane and ammonia
3) When everything settled down, the earth’s atmosphere was mostly CO2 and water vapour. There was very little oxygen
4) The water vapour later condensed to form oceans
What is phase 2 of the atmosphere forming?
Next 2 Billion years
1) Lots of the CO2 dissolved into the oceans
2) Nitrogen Gas entered the atmosphere
-> The Amount of N2 in the atmosphere increased as its unreactive so was being formed but not broken down
3)** Green plants evolved all over the earth, as they photosynthesised, they removed CO2, and produced O2**
-> Due to the plants, the amount of O2 in the air gradually built up and much of the CO2 got locked up in sedimentary rocks and fossil fuels
How did nitrogen enter the atmosphere in phase 2?
Formed by ammonia reacting with oxygen and was released by dentrifying bacteria
What is phase 3 of the atmosphere forming?
1) The build up of O2 in the atmosphere killed off early organisms that couldnt tolerate it
2) Allowed the evolution of more complex organisms that made use of the oxygen
-> The Oxygen also created the ozone layer (O3) which blocked harmful rays from the sun and enabled even more complex organisms to evolve
There is virtually no CO2
What is the balance of chemicals in our atmosphere?
Approximately 78% nitrogen
Approximately 21% nitrogen
Small amounts of other gases (each making up less than 1% of the atmosphere), Mainly CO2 and other noble gases and water vapour
Lifestyle
How has the increase of the human population/activity affected the composition of air? - Lifestyle
More people = More energy is needed for lighting, heating, cooking, transport and so on
Lifestyle - More countries are becoming industrialised and well-off - means the average energy demand per person is also increasing ( since people have more electrical gadgets, cars or travel on planes ect.)
This increased energy consumption comes mainly from the burning of fossil fuels, which releases more CO2
Land
How has the increase of the human population/activity affected the composition of air? - Land
More people = more land is needed to build houses and grow food - Often made by deforestation.
-> Plants are the main things taking CO2 out of the atmosphere (via photosynthesis) - so fewer plants means less Carbon Dioxide being taken out of the atmosphere
What is another reason for the rise in CO2?
Volcanoes erupting
What does the greenhouse effect do?
Keep the Earth warm
-> The sun gives out Electromagnetic radiation
-> Some EM radiation, at most wavelengths, passes through the atmosphere
->The EM radiation with short wavelengths is absorbed by the Earth, warming our planet
How does the Greenhouse Effect work?
1) The Earth radiates some of the heat radiation it absorbs as longer wavelength, IR radiation
2) Some of this IR radiation is absorbed by greenhouse gases
3) Some of the IR radiation is re-emitted back towards earth by greenhouse gases/ or into space
The absorbtion or re-emmision of IR radiation by greenhouse gases is what keeps the Earth warm
What are greenhouse gases?
what are some examples?
Gases in the atmosphere that can absorb and reflect heat radiation.
These are only present in small amounts
Carbon dioxide, water vapour and Methane
What happens if the concentration of greenhouse gases increases?
You get an enhanced greenhouse effect
-> This is where more heat radiation from the Earth is absorbed and re-emitted back into space - this causes the heating of the atmosphere
How does the increase of greenhouse gases (methane) cause climate change?
Concentration of Methane Risen (still only tiny amounts in atmosphere) but its an issue as it is super effective greenhouse gas
Why has the concentration of methane risen?
Its produced in the digestive process of certain livestock (e.g. Cattle, goats and camels).
So the more livestock we farm, the more methane produced
What is global warming?
There is a scientific consensus that extra greenhouse gases from human activity have caused the average temperature of the Earth to increase, due to the enhanced greenhouse effect
Global warming is a type of climate change that causes other climate change
What climate change could global warming cause?
Changing rainfall patterns
Severe flooding - ice caps melting
How accurate are mesurements of current global temperature and CO2 levels?
pretty accurately as theyre taken from all over the world
How accurate is historical data of global temperature and CO2 levels?
Less accurate than current data
-> Less data was taken over fewer locations and methods used to collect data was less accurate
-> If you go far back enough, no records are present.
What ways are used to estimate past data of global temperature and CO2 levels?
Analyse fossils, tree rings or gas bubbles trapped in ice sheets to estimate past levels of atmospheric carbon dioxide
-> These are much less precise than current sampling, and also less representitive of global data
What is needed to do to reduce climate change?
Cut down on the amount of greenhouse gases we are releasing into the atmosphere
How can we reduce carbon dioxide emissions?
try to limit our use of fossil fuels
Personal level: Walking or cycling instead of driving, or turning your central heating down
Larger level/scale: The Uk has formed plans to encourage the public and industry to become more energy efficient, to create financial incentives to reduce CO2, to use more renewable energy and to increase research into new energy sources
What is the flame test
The flame test - to identify metal ions
-> Compounds of some metals produce a characteristic color when heated in a flame, you can test for various metal ions by putting your substance in a flame and seeing what color the flame goes
In a Flame test, what color do Lithium ions turn?
Li⁺ gives a crimson red flame
In a Flame test, what color do Sodium ions turn?
Na⁺ gives a yellow flame
In a Flame test, what color do Potassium ions turn?
K⁺ gives a lilac flame
In a Flame test, what color do Calcium ions turn?
Ca2⁺ gives an orange-red flame
In a Flame test, what color do Copper ions turn?
Cu2⁺ gives a green flame
How do you carry out a flame test?
1) Clean a nicrome wire loop by dipping it into hydrochloric acid then rinsing it in distilled water
2) Then dip the wire loop into a sample of the metal compound and put the loop in the clear blue part of a bunsen flame (hottest)
3) Record what color the flame goes
What is the colored precipitate test with NaOH
Precipitate with NaOH - Test for metal ions
-> Many metal hydroxides are insoluble and precipitate out of solution - some of these have a characteristic color
For this test, you add a few drops of sodium hydroxide solution to a solution of your mystery compound, if a hydroxide precipitate forms, you can use its color to tell which metal ion is present
In the Metal hydroxide (NaOH precipitate) test, what color does aluminium turn INITIALLY?
White
Al³⁺(aq) + 3OH⁻(aq) -> Al(OH)₃(s)
In the Metal hydroxide (NaOH precipitate) test, what color does aluminium turn after it is redissolved in excess NaOH?
Colorless
Al(OH)₃(s) + OH⁻ -> Al(OH)₄⁻
This differs it from Calcium, which stays white
In the Metal hydroxide (NaOH precipitate) test, what color does Calcium turn?
Ca²⁺
White
Ca²⁺(aq) + 2OH⁻(aq) -> Ca(OH)₂(s)
In the Metal hydroxide (NaOH precipitate) test, what color does Copper turn?
Cu²⁺
Blue
Cu²⁺(aq) + 2OH⁻(aq) -> Cu(OH)₂(s)
In the Metal hydroxide (NaOH precipitate) test, what color does Iron(II) turn?
Fe²⁺
Green
Fe²⁺(aq) + 2OH⁻(aq) -> Fe(OH)₂(s)
In the Metal hydroxide (NaOH precipitate) test, what color does Iron(III) turn?
Fe³⁺
Brown
Fe³⁺(aq) + 3OH⁻(aq) -> Fe(OH)₃(s)
What is the test for ammonium ions?
(NH₄⁺)
Add some sodium hydroxide (NaOH) solution to the unknown solution and gently heat it
-> If ammonia gas is given off, ammonium ions are present
You can test for ammonia gas by holding a damp red litmus paper over it, If ammonia is present, it turns blue
What can ammonia gas be indentified by? Why is this unsuitable?
Very distinctive strong smell, but its not a good idea to go sniffing mystery gasses e.g. at high concentrations ammonia is an irritant and toxic
What are the tests for cations?
Flame test
NaOH precipitate
NaOH - Ammonia
What is the test for halide ions?
Silver nitrate solution - test for Cl⁻, Br⁻, I⁻
- Add some dilute nitric acid (HNO₃), followed by a few drops of silver nitrate solution (AgNO₃)
Nitric acid to get of carbonate ions - produce white precip
During the test for halide ions, what does chloride do?
Chloride gives a white precipitate of silver chloride
Ag⁺(aq) + Cl⁻ (aq) -> AgCl (s)
During the test for halide ions, what does bromide do?
Bromide gives a cream precipitate of silver bromide
Ag⁺(aq) + Br⁻ (aq) -> AgBr (s)
During the test for halide ions, what does iodide do?
Iodide gives a Yellow precipitate of silver iodide
Ag⁺(aq) + I⁻ (aq) -> AgI (s)
What is the test for carbonates?
To test for carbonate ions ( CO₃²⁻), add some dilute acid
- If there are carbonate ions present, the mixture will fizz - this is because the carbonate will react with the acid to produce carbon dioxide gas:
Carbonate ions + acid -> Carbon dioxide + water
CO₃²⁻ + H₂ -> CO2 + H2O
You can check to see if a gas if CO2 by bubbling it through limewater. If it is CO2, the limewater turns milky
What is the test for sulfate ions?
To test for sulfate ions in solution, first add some dilute hydrochloric acid - this stops any precipitation reactions not involving sulfate ions from taking place
Then add some barium chloride solution - if there are sulfate ions in the solution, a white precipitate will form
Barium ions + Sulfate ions -> Barium sulfate
Ba²⁺ (aq) + SO₄²⁻ (aq) -> BaSO₄ (s)
What is flame photometry?
It is an instrumental method that allows you to identify ions in a dilute solution
-> each ion produces a unique line spectrum with different lines present in different places
->The intesnity of the mesured wavelength indicates the concentration of the ion in that solution.
how do you work out concentration in flame photometry?
using a calibration curve
If the graph is plotted as Emmision intensity/Conc, follow the y to the x (concentration)
How does flame photometry work for mixtures?
A solution may give a spectrum which is a combination of 2 spectrums, so this can be compared to the individual ion spectrums
This makes it more useful than flame tests
What are the advantages of instrumental analysis (like flame photometry)?
Very sensitive - can detect the tiniest amount of substances
Very fast and tests can be automated
Very accurate - they dont involve human error, like manual analysis does
Homologous Series
a group of chemicals that have similar chemical structures
What is the general formula for alkAnes?
CₙH₂ₙ₊₂
A for additional Hydrogen
What are the names for the first 4 alkanes?
Methane CH₄
Ethane C₂H₆
Propane C₃H₈
Butane C₄H₁₀
What are the prefixes for alkanes/alkenes
Meth
Eth
Prop
But
Pent
What is an isomer?
Molecules with the same molecular formula but different arrangement of atoms
Unsaturated
Why are alkanes saturated?
They have formed bonds with as many other atoms as they can
How many bonds can carbon make (fully)
4
How many bonds can hydrogen make (fully)
1
What makes alkenes different from alkanes?
Alkenes have a double C=C bond
What is the alkenes functional group?
C=C
Functional group is defined as a particular group of atoms which are responsible for how a molecule reacts
What is the general formula for Alkenes?
CₙH₂ₙ
Why are alkenes unsaturated?
they can make more bonds - the C=C double bond can open up, allowing two carbon atoms to bond with other atoms
What are the first 3 alkenes?
Ethene C₂H₄
Propene C₃H₆
Butene C₄H₈
How does longer alkenes have isomers?
The double bond can go at the end of the chain or the middle
What are alkenes?
Homologous series of hydrocarbons with one functional group C=C
Alkanes are just considered a Homologous series of hydrocarbons
What is the test for alkenes?
Bromine water, when mixed with an alkene, the alkene will de-colorise bromine water, turning it from orange to colorless.
This is due to an addition reaction that takes place where bromine is added across the alkene double bond
Alkanes wont react as they are saturated
Why doesnt alkenes have methene?
CH2 wouldnt work due to not full bonds
What happens during alkane/alkene combustion reactions?
They are burnt in oxygen
What happens during alkane/alkene COMPLETE combustion reactions?
Alkane/ene + oxygen -> Carbon Dioxide + Water
What are polymers?
Substances of high average relative molecular mass made by joining up lots of small repeating units called monomers
What is addition polymerisation?
When lots of unsaturated monomer molecules ( Alkenes) open up their double bonds and join together to form polymer chains
What is the name and formula for polymers?
E.g. Ethene
Poly(Substance)
Poly(ethene)
(Substance)n
(C2H4)n
What are some examples of addition polymers?
Poly(tetrafluoroethene) (PTFE), Poly(chloroethane) (PVC),
Poly(ethene)
Poly(propene)
What are Poly(ethene)’s propeties and uses?
Properties:
Flexible, electrical insulator, cheap
Uses:
Plastic bags, bottles, wire insulation
What are Poly(propene)’s propeties and uses?
Properties:
Flexible, strong, tough, mouldable
Uses:
Crates, furniture, ropes
What are Poly(chloroethene)’s (PVC) propeties and uses?
Properties:
Tough, cheap
Uses:
Window frames, water pipes
What are Poly(tetrafluoroethene)’s (PTFE) propeties and uses?
Properties:
Unreactive, tough, non-stick
Uses:
Non-stick pans, waterproof clothing
What are polyesters made by
Condensation polymerisation
when dicarboxylic acid monomers and diol monomers react together
What does condensation polymerisation usually involve?
2 Monomers (reactants) making 2 products, one of which being a small molecule e.g. H2O or HCl
The monomers react together and bonds form between then, making polymer chains. Each monomer has at least 2 functional groups, one on each end of the molecule.
Each functional group can react with the functional group of another monomer, creating long chains of alernating monomers. For each new bond that forms, a small molecule is lost
What link/bond is formed when the carboxylic acid group reacts with the alcohol group?
An ester link
-> In Polyesters, formed out of condensation polymerisation, each time an ester bond is formed, a molecule of water is lost
What are some examples of useful non-synthetic polymers?
Synthetic = Man-made
DNA
Amino Acid
Carbohydrates
Starch/cellulose
Polymers
DNA
DNA is complex molecule that contains genetic information
It contains two strands and each strand is made up of nucleotide monomers that bond together in a polymerisation reaction
DNA is made from 4 different monomers called nucleotides
Polymers
Amino acids
Amino acid monomers form polymers known as protiens via condensation polymerisation.
Protiens have many important uses in the human body e.g. enzymes
Polymers
Carbohydrates/Starch
Carbohydrates are molecules containing carbon, oxygen and hydrogen, used by living things to produce energy
Starch and cellulose are large, complex carbohydrates, which are made up of many smaller units of carbohydrates, known as sugars, joined in a large chain
What are synthetic polymers made from?
substance
Crude oil
What are plastics?
A type of polymer made from crude oil
Why is the price of crude oil products increasing?
It is a finite resource, the more it is used up, the more expensive it will become
How many tonnes of plastic are produced by the UK each year?
Over 2 Million tonnes
What are the 2 main ways to dispose polymers?
Landfill sites
Combustion
What are the negatives of disposing polymers in landfill?
1) Alot of plastics get dumped in landfill sites. This is usually when different polymers are too dificult or expensive to seperate and recycle
2) Lots of valuable land is quickly getting used up for use and landfill sites
3) Most polymers are non-biodegradeable - they wont decompose and so will sit in landfill for forever
What are the negatives of disposing polymers by combustion?
1) Burning plastics produces energy - used to generate electricity
2) In not carefully controlled, toxic gases can be released from the combustion of plastics
3) Carbon Dioxide is also produced - Global warming
What is an example of toxic gases being released during polymer combustion (for disposal)
Polymers that contain chlorine ( such as PVC), produce HCl when burned
What are the advantages of recycling polymers
Reducing use of crude oil
- Reduces the amount of non-biodegradeable waste filling up landfill sites
- Reduces emmisons of greenhouse and toxic gases which can be released from burning polymers
- Uses up less water/energy than when making new plastics
- Reduces usage of crude oil
- Saves money and creates jobs
What are the disadvantages of recycling polymers
Reducing use of crude oil
1) Polymers must be seperated by type before they can be melted and reformed into a new product - difficult/expensive
2) If polymers are mixed together, the quality of the final recycles polymer product could be reduced
3) Polymers can only be recycled a finite number of times - overtime strength of polymer can decrease
4) Melting down polymers can release dangerous gases into the atmosphere - harmful to animals / plants
What is fermentation?
the process of using yeast to convert a type of carbohydrate called sugars into alcohol
What is the equation for fermentation?
Glucose -> Ethanol + Carbon Dioxide
C₆H₁₂O₆ -> 2C₂H₅OH + 2CO₂
-> features the enzymes in yeast (naturally occuring catalyst)
where does the carbohydrate come from for fermentation?
Any source, but sugar cane and sugar beet plants are often used
How do you make a solution of ethanol by fermentation?
1) Mix yeast and a solution of carbohydrate ( e.g. glucose) in a clean container. Seal and leave in a warm place
2) Keep mixture between 30°C and 40°C and in aerobic conditions
3) When the concentration of alcohol reaches about 10%-20% the fermentation reaction stops because the yeast gets killed off by the alcohol
4) The yeast will fall to the bottom of the container - you can collect the ethanol solution from the top
Why is the mixture kept between 30°C and 40°C for fermentation?
Fermentation happens fastest between these temperatures. At lower temperatures, the reaction slows down.
If its too hot the enzyme in the yeast denatures and the reaction would stop.
Why is the mixture kept in anaerobic conditions during fermentation?
Oxygen converts the ethanol to ethanoic acid ( the stuff in vinegar) - unwanted
How can fermented solution be processed to produce a more concentrated alcohol?
The fermented solution can be distilled to produce more concentrated alcohol
different types of alcoholic drinks contain different concentrations of alcohol
To convert a dilute concentration of ethanol (produced by fermentation), with a conc of over 20%, fractional distillation is used
Where are common alcohols distilled from?
Brandy is distilled from wine
whiskey is distilled from fermented grain
Vodka is distilled from fermented grain or potatoes
How is fractional distillation used to concentrate ethanol
Fractional distillation seperates mixtures by heating them.
Ethanol has a lower boiling point than water. This means that when the fermentation mixture is heated, ethanol evaporates and the vapour rises up the fractioning column, while the water stays as a liquid
A liebig condenser is used to condense the ethanol vapour by cooling it. The concentrated ethanol can then be collected in a seperate flask
What functional group do alcohols have?
-OH
What is the general formula for alcohols?
CₙH₂ₙ₊₁OH
When reacting with oxygen, what do alcohols do?
Combustion
Alcohol + Oxygen -> Carbon Dioxide + Water
How does the alcohol naming system work?
Use their alkane name but repla ce the end with “ol”
Methane -> Methanol
What happens if you heat a mixture of an alcohol and an acid catalyst?
An alkene and water are formed.
-> This is called a dehydration reaction, because a molecule of water is lost from the alcohol for each alkene molecule formed
What are alcohols oxidised to form (using an oxidising agent)?
Carboxylic acids
They are oxidised - they gain oxygen
What properties do solutions of carboxylic acids share with other acids?
- They react like acids e.g. they react with carbonates to produce CO2, a salt and water
- In solution, they partially ionise and release H+ ions, which makes the solution weakly acidic
What is the basic naming system for Carboxylic acids?
Alkanes but replace the final “e” with “oic acid”
e.g. Ethanoic acid
Which of the homologous series doesnt have a meth prefix?
Alkenes, it starts with Ethene due to Methene not having complete covalent bonds
What is the homologous series Carboxylic acids general formula?
Cₙ₋₁H₂ₙ₋₁COOH
What is the homologous series Carboxylic acids functional group?
COOH
How are alcohols useful as fuel?
when they’re burned, they release energy
What do some countries that have little or no oil deposits but plenty of land and sunshine do?
grow sugar cane, which they ferment to form alcohol. The ethanol can then be helped to fuel cars
Practical: Testing which alcohol is best to heat up a specific volume of water
1) Put some alcohol into a spirit burner and mesure the mass of the burner and fuel using a mass balance
2) Mesure 100cm3 into a copper calorimeter, insulate it by using a draught excluder, then cover it with an insulating lid after placing a thermometer inside - minimise heat energy loss
3) Take the initial temperature of the water then put the burner under the calorimeter and light the wick.
4) Stir the water throughout using the thermometer. When the heat from the burner has made the water temp rise by 20C, blow out the spirit burner
5) Immediately reweigh the burner and fuel
repeat the experiment using other alcohols
What precautions should be done when handling alcohols?
Theyre hazardous to humans - methanol is toxic and propanol is an irritant
-> Gloves and safety glasses
Alcohol is highly flammible so direct contact with the flame should be avoided.
-> Just light the wick
The heat they expel makes apparatus hot, so let it cool down before touching it
What are the controls in the alcohol energy test?
Using the same copper calorimeter each time
Vol/mass of water
Height of the container above the wick
Length of wick/height of flame
Number of moles of alcohol
In the burning alcohols practical, what do the results indicate?
Less alcohol burned = better fuel
-> longer chain of carbon = more efficient
What are strong, rigid polymers used for?
E.g. High-density poly(ethene)
used to make water pipes
What are light, strechy polymers used for?
E.g. Low-density poly(ethene)
Plastic bags and squeezy bottles
What is poly(styrene) foam used for?
packaging to protect breakable things, and as a thermal insulator
What are heat-resistant polymers used for?
E.g. Melamine resin and poly(propene) are used to make plasic kettles
How are ceramics made?
Made by baking substances, such as clay, to produce a brittle, stiff material
e.g. Glass, porcelain and bone china
What is clay?
A mineral formed from weather and decomposed rock. Its soft when its dug up out of the ground, which makes it easy to mold into different shapes required for pottery or bricks
It can be hardended by firing at very high temperatures. This makes it ideal as a building material - clay bricks can withstand the weight of lots more bricks ontop of them
What is glass generally like?
Transparent and strong, and can be moulded when hot and can be brittle when thin
How is the majority of glass made?
The majority of glass made is soda-lime glass which is made by heating limestone, sand and sodium carbonate (Soda) untill they melt. When the mixture cools it comes out as glass
What are some common composites and how are composites made?
Fibreglass and concrete
- Made of one material ( the reinforcement) embedded in another (the matrix/binder)
Their properties depend of what theyre made from
What are some examples of composites and their properties?
What does this make them ideal for?
Carbon fibre composites have been made using carbon atoms bonded together to make carbon fibres or carbon nanotubes held together in a polymer resin matrix.
These polymers are expensive to make but very strong and light making them ideal for use in aerospace and sports car manufacturing
How dense and malleable are metal normally?
High density and malleable
What is tensile strength?
how easily it breaks
How are polymers suited to different jobs?
Polymers are very adaptable
- Often flexible - bent without breaking
- Easily moulded into different shapes
- Cheaper and less dense than most metals/cermics
–> Often used designing products that need less mass
- Thermal and electrical insulators
- They degrade/break down over time
–> Dont always last as long as other materials
How are ceramics suited to different jobs?
- Like polymers, they’re good insulators of heat and electricity
- Brittle and stiff — but also strong and hard wearing
- They dont degrade or corrode like other materials
–> They last longer, why we use glass in windows instead of clear plastic
How are metals suited to specific jobs?
- Good condutors of heat/electricity - Advantages/disadvantages
- Malleable - molded into different shapes
- Some corrode easily, but products made from corrosion-resistant metals can last for a long time
- Less brittle, so less likely to shatter
How are composites suited to specific jobs?
- Different properties depending on the matrix/binder and the reinforcement.
- The combination of component materials can be altered, so composites can be designed to have specific properties for specific purpose
- But these are more expensive than other materials
