C9 - Crude oil and fuels Flashcards
Where do we find Crude oil ?
-Crude oil is found in rocks .
What type of resource is crude oil ? Give the definiton .
Crude oil is a finite resource - if we continue to use it it will one day runout .
How is Crude oil formed ?
-Crude oil is formed over million of years , from the remains of tiny sea creatures called plankton which were buried in mud .
What is Crude oil a mixture of ?
-Crude oil is a mixture of molecules called hydrocarbons .
What are hydrocarbons ?
Hydrocrbons are molecules made up of only hyrdogen and carbon atoms only .
Examples of crude oil hydrocarbons .
Methane , Ethane , Propane and Butane .
What do scientists call hydrocarbons like methane and ethane ?
Alkanes
Formula for Methane and draw it .
CH₄
Formula for Ethane and draw it .
C₂H₆
Formula for Propane and draw it .
C₃H₈
Formula for Butane and draw it .
C₄H₁₀
What is a homoglyous series ?
A group of compounds with similar properites that differ by CH₂
Scientists say Alkanes are SATURATED , why ?
As the carbon atoms are fully bonded to hydrogen atoms in alkanes .
Meaning of Viscosity
- How thick a fluid is .
- Fluids with high viscosity , flow slowly .
As the size of hydrocarbon molecules increases , what happens to the viscosity ?
-The molecules become more viscous , very long chain hydrocarbons flow very slwoly - extremely viscous .
Meaning of Flammability ?
Tells us how easily a hydrocarbon combusts (burns).
Describe flammability of hydrocarbons .
- Short chain hydrocarbons are extremely flammable .
- As the size of the hydrocarbon molecules increses , the molecules become less flammable - long chain hydrocarbon are extremely difficult to burn .
Meaning of boiling point ?
-The temperature at which a liquid turns into a gas .
Boiling point of short chain hydrocarbons .
-Low boiling points
(Methane , Ethane , Propane and Butane are gases at room temperature , as their boiling points are lower than room temperarture .)
What happens to the boiling points as the size of the hydrocarbon molecule increases ?
-The boiling point also increases , very long chain hydrocarbons have very high boiling points .
What needs to be done for crude oil to be useful ?
-The hydrocarbons in crude oil have to be separated .
How do we seaparate hydrocarbons in crude oil ?
Fractional distillations where crude oil is separated into fractions .
What are fractions ?
- Fractions contain hydrocarbons with a similar number of carbon atoms .
- a group of compounds with simialr boiling points and chian lengths .
Where does fractional distillation take place ?
-It takes place in very large colums found in oil refineries .
What is the first stage of fractional distillation of crude oil ?
-The crude oil is heated to a veyr high temperature , this causes the crude oil to boil -all the hydrocarbons evaporate and turn into gas .)
What is the second stage of fractional distillation of crude oil ?
-The crude oil is now fed into the fractional distillation column . The column is hotter at the bottom and cooler at the top .
Last few steps of fractional distillation of Crude Oil .
- The hydrocarbon vapours now rise up the column .
- Hydrocarbons condedse (turn back into liquid ) when they reach their boiling point .
- Liquid fractions then removed .
- Remaining hydrocarbons continue moving up the column , there they now condense when they reach their boiling point.
Where is it hto and cold in a fractional distillation collumn ?
Hot at the bottom - liquid .
Cool at the top - gas .
Where are long chain hydrocarbons removed in fractional distillation?
-Long chain hydrocarbons have a very high boiling point , these hydrocarbons are removed from the bottom of the column .
Where are short chain hydrocarbons removed in fractional distillation ?
-Very short chain hydrocarbons have very low boiling points , these do not condense , they re removed at the top of the column as gases .
How are some fractions used
- As fuels - petrol and diesel .
- As feedstock for the petrochemical industry .
What is feedstock ?
A chemical used to make other chemicals -e.g detergents .
Meaning of combustion
Burning
Meaning of Volatility
-How easily a substance turns into a gas .
Volatitlity of short chain hydrocarbons :
-High volatility
Volatility of long chain hydrocarbon :
-Low Volatility
How do Hydrocarbons release energy ?
-Hydrocarbons release energy when combusted (burned)
What happens during combustion of hydrocarbons ?
During combustion , the carbon and hydrogen atoms in the fuel react with oxyegn . The carbon and hydrogen are oxidised .
What happens in complete combustion ?
-The oxyegn is unlimited , this reaction produces carbondioxide and water .
Balance the complete bustion of propane ?
C3H8+02—> What are the products ? balance it .
Check sheet .
What is incomplete combusion ?
-When there is not enoguh oxyegn ot react with the fuel . Products are carbon MONOXIDE (CO) and water .
Products of complete combusiton :
CO2+H20 (carbon dioxide and water )
Products of incomplete combustion :
CO+H20 (carbon monoxide and water)
What is a homologous series ?
-A group of compounds with similar properties that differ by CH2 .
When will a liquid condense ?
-At its boiling point .
Why are smaller alkanes more desirable ?
-As smaller alkanes are cleaner when burnt (less smoky than large alkanes . Smaller alkanesare more easier to burn compared to large alkanes .
What condition is required for complete combustion to occur ?
-Plenty of oxygen for the fuel to react .
What condition is required for complete combusiton to occur ?
Plenty of oxygen for the fuel to react .
What are two key features of alkanes ?
- General formual CnH2n+2
- ( Main one ) Alkanes only have SINGLE covalent bonds between the carbon atoms .
Why don’t long chain hydrocarbons make good fuels , what can we do to solve this ?
- They do not as they are not flammable .
- Issue is that there is a high demand for short chain hydrocarbons , so gotta convert long chain hydrocarbons into shorter ones through a process called cracking .
What happens during cracking ?
A long chain alkane is broken down (cracked) to produce smaller , more useful moleucles .
What are the products of cracking ?
-You have the short chain hydrocarbons produced but cracking also produce hydrocarbons known as ALKENES .
What are the two ways that can be used for cracking ?
- Catalytic Cracking
- Steam Craking .
How does catalytic cracking work ?
-In catalytic cracking , we use high temperature and catalysts which speed up the reaction .
How does steam cracking work ?
-In steam cracking you use , steam and high temperature .
What bonds do alkenes have ?
-Alkenes have DOUBLE covalent bonds between two carbon atoms (unlike alkanes) .
Alkenes are useful molecules , how can they be used ?
- They are used to make chemicals called polymers .
- Alkenes are also used as the starting material for other useful chemicals as well .
Reactvity of alkenes .
Alkenes are MORE REACTIVE than alkanes . Can use this to test for alkenes .
What is the test for alkenes ?
-We test for alkenes using bromine water which is orange .
-Of we shake our alkene with bromine water .
-The bromine water turns colourless .
VERY IMPORTANT YOU SAY COLOURLESS NOT CLEAR IN EXAM ..
do some balance equations for cracking
(check sheet if stuck )
What is the MOLECULAR formula of ethene ?
C2H4
What is the displayed formula , what is the displayed formul of ethene ?
The displayed formula shows us all the atoms and the covalent bonds .Check sheet .
What is the general formula for alkenes ?
C2H2n - If we know the number of carbon atoms (n) , we can calculate the number of hydrogen atoms by X2 the number of carbon atoms .
Where can you put double bonds in alkenees ?
-In GCSE between any two adjacent carbon atoms .
What four alkenes do you need to know ? Write the molecular formula for theemm and the displaed formula .
-Ethene
-Propene
-Butene
-Pentene
Check seet for answers .
Why do scientists say that alkene molecules are unsaturated ?
-As alkenes have two fewer hydrogen atoms than the alkane with same number of carbon atoms .
ETHANE has six hydrogens but ETHENE has four hydrogens , they both have same number of carbon atoms .
Why do all alkenes react in a similar way ?
As all alkenes have a double bond .
What do scientists call the double bond in alkenes ?
-The Alkene functional group .
What is the meaning of a “functional group”
The part of the molecule that determines how it reacts .
-All alkenes have the same fuctional grup (carbon co carbon double bond.)
Scientists call molecules like alkenes a homologous series , what does that mean ?
- Molecules of a homologous series has the same fuctionl group and the same formula and difer by CH2
- Each molecule in the homologouse series has an extra carbona tom and two extra hydrogen atoms /
What are the products of the combustion of alkenes ?
-Produce carbondioxide and ater like alkanes .
-However , incomplete combustion of an alkene also produces unburnt carbon paerixles , this is because of incomplete combstion .
As a result , alkenes burn in air with a smoky flame .
What are the requirements of hydrogenation ?
- This reaction requires a temperature of around 150 degrees .
- Also requires a nickel catlayst to speed up the reaction .
How are the hydrogen atoms added in hydrogenation ?
- The two hydrogen atoms are added across the double bond .
- The carbon to carbon double bond is converrted ino a carbon to carbon single bond .
What happened to the hydrogenaiton reactionn ont he page .
So what does reacitng an alkene with hydrogen produce ?
- It converted ethene into the alkane ethane .
- Reacting an alkene with hydrogen produces an alkane .
-What fractions of crude oil are usually cracked
Naptha
-Why are they cracked
-To rpoduce moe useful and shorter chain alkanes .
-What type of reaction is cracking ?
-Thermal decompostion - when a compound breaks down when heated .
What are the two products formed in cracking ?
- Short chain alkane
- alkene .
meaning of combustion (burning)
-The reaction of something with oxygen .
Give for useful products from fractional distillatio .
- Solvents
- Lubricating oils
- Fuels
- Detergents
