Topic 8- fuels Flashcards
What are hydrocarbons
A compound that contains carbon and hydrogen only
Describe a crude oil- 5 points
A complex mixture of hydrocarbons
Containing molecules in which carbon atoms are in chains or rings
An important source of useful substances (fuels and feed stock for the petrochemical industry)
A finite resource
Non renewable
How do we separate crude oil
We separate crude oils into simpler more useful mixtures by the process of fractional distillation
List the fractions in fractional distillation, in order from top to bottom (lowest bp to highest bp)
Gases Petrol Kerosene Diesel oil Fuel oil Bitumen
Recall the names and uses of the fractions from top to bottom (lowest bp to highest bp)
Gases- domestic heating and cooking
Petrol- Fuel in cars
Kerosene- Fuel for aircraft
Diesel oil- fuel for some cars and trains
Fuel oil- fuel for large ships and in some power stations
Bitumen-used to surface roads and roofs
What is fractional distillation
A tall fractionating column is fitted above the mixture, with several condensers coming off at different heights. The column is hot at the bottom and cool at the top. Substances with high boiling points condense at the bottom and substances with lower boiling points condense on the way to the top.
List how hydrocarbons in different fractions differ from each other
The number of carbon and hydrogen atoms their molecules contain
boiling points
ease of ignition
viscosity
and are all mostly members of the alkAne homologous series.
Explain a homologous series as a series of compound which…
Have the same general formula
Differ by CH2 in molecular formula from neighboring compounds
Show a gradual variation in physical properties, as exemplified by their boiling points
Have similar chemical properties
Describe the complete combustion of hydrocarbon fuels as a reaction in which…
Carbon dioxide and water are produced
Energy is given out
What is incomplete combustion
incomplete combustion occurs when the supply of air or oxygen is poor. Water is still produced, but carbon monoxide and carbon are produced instead of carbon dioxide.
Explain why the incomplete combustion of hydrocarbons can produce carbon and carbon monoxide
Part of the carbon is not completely oxidised which therefore produces soot or carbon monoxide.
How does carbon monoxide behave as a toxic gas
When breathed in it displaces the oxygen in the blood, the bond between carbon monoxide and haemoglobin is so much stronger than the bond with oxygen. Oxygen is then unable to access vital organs and destroys cells.
Describe the problems caused by incomplete combustion producing carbon monoxide and soot in appliances that use
carbon compounds as fuels
It blocks pipes carrying waste gases from an appliance and blacken/ stain buildings- soot
What can impurities in some hydrocarbon fuels result in and why
Most hydrocarbon fuels burnt aren’t pure and therefore naturally contain some sulfur compounds (impurities). When the fuel burns, the sulfur it contains is oxidised to sulfur dioxide
How does sulfur dioxide cause acid rain and what are some problems associated with acid rain
Sulfur dioxide dissolves in water droplets in clouds, this makes the rain more acidic. Acid rain reacts with metals and rock such as limestone (corrodes them) Makes soil and water acidic which kills off wildlife.
Why, when fuels are burned in engines can oxygen and nitrogen react together at high temperatures
At high temperatures nitrogen and oxygen from the air combine to produce nitrogen monoxide and other oxides. Coal is made mainly from carbon, when this burns carbon dioxide is produced. When nitrogen monoxide is released the vehicles exhaust system combines it with oxygen in the air to form nitrogen dioxide. ????
Evaluate the advantages and disadvantages of using hydrogen, rather than petrol as a fuel in cars
Hydrogen doesn’t generate carbon dioxide when burnt
Hydrogen fuel cells are very efficient
HOWEVER
There are few filling stations that sell hydrogen
Hydrogen must be compresses and liquefies, then stored in tough insulated fuel tanks
Hydrogen fuel cells do not work at very low temperatures and they may require a platinum catalyst which is very expensive
List the non renewable fossil fuels obtained from crude oil and an example of a non renewable fossil fuel found in natural gas
petrol, kerosene and diesel oil are non-renewable
fossil fuels obtained from crude oil and methane is a nonrenewable
fossil fuel found in natural gas
What does Cracking involve
Breaking down a larger saturated hydrocarbon molecule ( alkAnes) into smaller, more useful ones, some of which are unsaturated (alkEnes)
Why is cracking necessary
To match supply with demand
What are the differences between alkAnes and alkEnes?
AlkAnes- Saturated, form a single bond C-C
AlkEnes- Unsaturated, form a double bond C=C
Whats the equation for complete combustion
Hydrocarbon+Oxygen–> Carbon Dioxide + Water
Whats the equation for incomplete combustion
Hydrocarbon+Oxygen—> Carbon monoxide+Carbon+Water
What’s the general formula for AlkAnes
CnH2n+2
What’s the general formula for alkEnes
CnH2n
What names are there for the number of Carbons.
Meth 1 Eth 2 Prop 3 But 4 Pent 5 Hex 6
In alkanes what does a longer chain mean
A higher boiling/melting point
Can alkanes do addition reactions
They are saturated and only have single bonds (everything has something attached) therefore they cannot
Can alkEnes react
Yes because they are unsaturated, there is room for addition of molecules
What happens when you react an alkAne with bromine water
The product retains the colour from the bromine solution (brown orange)
What happens when you react an alkEne with bromine water
The product is colourless
What is cracking
A chemical reaction in which large alkane molecules are split into 2 or more small alkanes and alkEnes
What can decane be cracked to for,
Octane and ethene
Give an explanation of the practical using paraffin oil in cracking
When paraffin oil is heated, it evaporates to form a gas. The paraffin gas passes over the hot pieces of porous pot. The heat causes some of the covalent bonds in the paraffin to break so the paraffin is cracked. An alkane with a shorter carbon chain is formed, ethene is also formed. It’s a gas so collects in the test tube
Why were first few bubbles of gas allowed to escape
They were just air from the boiling tube
What does a catalyst do
Lower activation energy
What is paraffin
Long hydrocarbon
What happens when the heat is removed
The gas left in the apparatus contacts.
If the end of the delivery tube is still under water the water will he forced up into the hot tube and the tube will crack, this is called suck back
What are alcohols
Organic molecules with a framework of carbon atoms to which hydrogen and other atoms are attached
What is the functional group of alcohols
-OH
What do all the names of alcohols end in
Anol
What’s the formula for ethanol
C2H5OH
What are carboxylic acids
A homologous series which all have the functional group- COOH
One of the oxygen in the group is joined to the carbon atom with a double bond
How do we make carboxylic acids
Oxidising alcohols
Ethanol + oxygen- ethanoic acid + water
What do smaller chains do
Dissociate more (more readily) as they have less bonds to break
What does a metal and an acid always produce
Hydrogen
What are polymers
Substances of high average relative molecular mass made up of small repeating units called monomers
What is a polymerisation reaction
Lots of monomers join up to make a polymer
Give 3 examples of synthetic polymers
Poly(ethene) made from Ethene monomers
Poly(propene) made from propene monomers
Poly(chloroethene) chloroethene
Give 3 examples of natural polymers
Starch- made from glucose
DNA- made from nucleotides
Protein- made from amino acids
Because the number of carbon atoms can vary we cannot give a formula for a polymer molecule how do we show addition polymerisation
Find the repeating unit
Opening the double bond and expanding the double bracket through
Put an n in the corner
What are the properties and uses of polyethene
Flexible cheap and good insulator
Used for plastic bags, bottles, cling film and polytunnels
What are the properties and uses of polypropylene
Flexible does not shatter
Used for buckets, bowls, crates, ropes and carpets
What are the properties and uses of polychloroethene (pvc)
Tough good insulator can be made hard or flexible
Used for window frames, gutters, pipes, insulation for electrical wires
What are the properties and uses of poly tetrafluoroethene (ptfe/ teflon)
Tough and slippery
Used for non stick coatings on frying pans and kitchen utensils, Burette taps, stain proofing clothing and carpets
How is poly(chloroethene) formed
Lots of chloroethene monomers joined up to make a long molecule
What is condensation polymerisation
Condensation polymerisation usually involves two different types of monomer.
The monomers react together and bonds form between them, making polymer chains.
Each monomer has to contain at least two functional groups, one on each end of the molecules.
Each functional group can react with the functional group of another monomer, creating long chains of alternating monomers. For each new bond that forms, a small molecule (e.g. Water) is lost.
What does condensation polymerisation make
Water
What happens when ethanol and ethanoic acid join
A molecule of water is Eliminated, the organic molecule formed is an ester called ethyl ethanol
What happens when ester bonds form
Water forms
What parts of molecules join to form the water
The -OH part of the carboxylic acid functional group and the H atom from alcohol functional group
The only remaining parts of the carboxylic acid and alcohol molecules join up to form an ester
What do all esters contain
A coo link
A carbon double bonded to an oxygen and then a single bond to an oxygen
What do you need to form a polyester
A carboxylic acid
An alcohol
Which both have functional group at both ends so they can join together to form H20
What is most polymer waste
Non biodegradable
Advantage and disadvantages of landfill
Maybe possible to extract and sell the methane produced
But
What uses valuable land and harmful substances leak into soil and water supply
Advantage and disadvantages of incineration
Produces useful energy
But
May produce harmful or toxic gases
Advantage and disadvantages of recycling
New items can be made, conserves supply of crude oil
But
Polymers need to be melted and items need to be collected, stored and washed
What forms when carboxylic acid monomers and alcohol monomers react together
Polyesters form
