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iGCSE Chemistry: Alkenes & polymers - test myself

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Explain the term hydrocarbon
A hydrocarbon is a molecule containing only hydrogen and carbon
Show the empirical formulae, molecular formulae, general formulae, structural formulae and displayed formulae of butane
Show the empirical formulae, molecular formulae, general formulae, structural formulae and displayed formulae of ethane
What is a general formula?
A formula to show the relative quantity of different types of atom for a molecules in a homologous series. Eg CnH2n+2 for alkanes
Explain the term functional group
A functional group is an atom or a group of atoms that determine the chemical properties of a compound
Explain the term homologous series
A homologous series is a family of compounds with 1) the same general formula 2) similar chemical properties 3) trends in their physical properties
What are isomers?
Molecules with the same molecular formula but with a different structure
Write all the possible different structural and displayed formulae of C₄H₁₀
Write all the possible different structural and displayed formulae of C₄H₈
Write all the possible different structural and displayed formulae of C₅H₁₂
In what type of reaction is an atom or group of atoms added to a molecule without taking anything away?
Addition reaction
In what type of reaction is an atom or group of atoms replaced by a different atom or group of atoms?
Substitution reaction
What is a substitution reaction?
A reaction where an atom or group of atoms is replaced by a different atom or group of atoms
What is an addition reaction?
A reaction where an atom or group of atoms is added to a molecule without taking anything away
What is combustion?
Combustion is burning a substance, and is a reaction with oxygen
What is crude oil?
A mixture of hydrocarbons
Explain how crude oil is separated into fractions
Crude oil is separated by fractional distillation. Crude oil is heated and the oil evaporates. It then goes into the tower. As the vapours rise up the tower the temperature falls. Different sized fractions condense at different heights because they have different boiling points. Smaller molecules condense high up the tower. Larger molecules condense low down in the tower. Then the fractions are collected.
What is the name of the process in which crude oil is separated into its various components?
Fractional distillation
Recall a use of bitumen
Surfacing roads
Recall a use of diesel
Fuel for lorries
Recall a use of fuel oil
Fuel for ships
Recall a use of gasoline
Fuel for cars
Recall a use of kerosene
Fuel for aeroplanes
Recall a use of refinery gases
Cooking
Recall a use for each of the 6 fractions obtained from the fractional distillation of crude oil
refinery gases=cooking; gasoline=fuel for cars; kerosene=fuel for planes; diesel=fuel for lorries; fuel oil=fuel for ships; bitumen=surfacing roads
Recall the names of the main fractions obtained from crude oil, in order of lowest boiling point first
Refinery gases, gasoline, kerosene, diesel, fuel oil and bitumen
Describe the trend in boiling points of the main fractions in crude oil
Boiling point increases as the number of carbon atoms (chain length) increase
Describe the trend in viscosity of the main fractions in crude oil
Viscosity increases as the number of carbon atoms (chain length) increase
In the fractional distillation of crude oil, how does boiling point change as the chains get longer?
Increases
In the fractional distillation of crude oil, how does viscosity change as the chains get longer?
Increases
What is meant by the term viscosity?
The viscosity of a fluid describes how easily it flows. Water has a low viscosity, it flows very easily. Crude oil has a higher viscosity than water, it does not flow very easily.
Which fraction of crude oil has the lowest boiling point?
Refinery gases
Which fraction of crude oil is the most viscous?
Bitumen
What does volatile mean? Which fraction of crude oil is the most volatile?
If a substance is volatile it evaporates easily. Refinery gas is the most volatile fraction of crude oil.
What is a fuel?
A fuel is a substance that, when burned, releases heat energy
What is a substance called if it, when burned, releases heat energy?
A fuel
Recall the products of the complete combustion of alkanes
Carbon dioxide and water
Recall the products of the incomplete combustion of alkanes
Carbon, carbon monoxide, carbon dioxide and water
What is produced when alkanes burn with insufficient oxygen?
Carbon monoxide and water (and possibly also carbon and carbon dioxide)
Write a chemical equation for the complete combustion of propane
C₃H₈ + 5O₂ → 3CO₂ + 4H₂O
Explain why carbon monoxide is dangerous to humans
It is poisonous because it reduces the capacity of the blood to carry oxygen
Why does incomplete combustion occur?
When there is an insufficient supply of oxygen for complete combustion
State the catalyst for the cracking of hydrocarbons
Aluminium oxide
State the conditions for the cracking of hydrocarbons
Aluminium oxide catalyst heated to 600°C
State the temperature for the cracking of hydrocarbons
600°C
What is cracking?
The breaking down of long-chain alkanes into alkenes and shorter-chain alkanes
When long chain alkanes are cracked, what is produced?
Shorter chain alkanes and alkenes
Write a chemical equation for the cracking of decane
C₁₀H₂₂ → C₂H₄ + C₈H₁₈
Crude oil contains a surplus of long chain alkanes and there is much higher demand for shorter chain alkanes. What process is used to deal with this imbalance?
Cracking
Explain why cracking is an important process in the oil industry
Cracking converts long chain hydrocarbons into short chain hydrocarbons. Crude oil contains a surplus long chains. Shorter chain hydrocarbons are in greater demand, e.g. petrol. Cracking also produces alkenes which are used in making polymers and ethanol.
State the general formula of alkanes
CnH2n+2
State the names and molecular formulae of the first 5 alkanes
methane (CH₄), ethane (C₂H₆), propane (C₃H₈), butane (C₄H₁₀), pentane (C₅H₁₂)
Explain the term saturated
A molecule containing only single bonds
Why are alkanes classified as saturated hydrocarbons?
They contain only single bonds
Draw the displayed formula for the two alkanes with the molecular formula C₄H₁₀
Draw the displayed formulae for butane
Draw the displayed formulae for ethane
Draw the displayed formulae for methane
Draw the displayed formulae for pentane
Draw the displayed formulae for propane
What is the molecular formula for butane?
C₄H₁₀
What is the molecular formula for ethane?
C₂H₆
What is the molecular formula for hexane?
C₆H₁₄
What is the molecular formula for methane?
CH₄
What is the molecular formula for pentane?
C₅H₁₂
What is the molecular formula for propane?
C₃H₈
State the conditions for the reaction of methane with bromine to form bromomethane
UV light
What are the two products of the reaction between methane and bromine? (2)
Bromomethane (CH₃Br) and hydrogen bromide (HBr)
What else is needed for methane to react with bromine?
UV light
What is the name given to the type of reaction that occurs when ethane reacts with bromine under UV light
Substitution
Would methane normally react with bromine?
No (because it is saturated)
Write the chemical equation for the reaction between methane and bromine
CH₄ + Br₂ → CH₃Br +HBr
Write the word equation for the reaction between methane and bromine
methane + bromine → bromomethane + hydrogen bromide
State the general formula for alkenes
CnH2n
Explain the term unsaturated
A molecule containing a carbon-carbon double bond
Why are alkenes classified as unsaturated hydrocarbons?
They contain a double bond
Draw the displayed formulae for butene
Draw the displayed formulae for ethene
Draw the displayed formulae for propene
Draw the displayed formulae for the two straight chain isomers of butene. Name these two isomers
State the names and molecular formulae of the first 3 alkenes
ethene (C₂H₄), propene (C₃H₆), butene (C₄H₈)
What is the molecular formula for butene?
C₄H₈
What is the molecular formula for ethene?
C₂H₄
What is the molecular formula for propene?
C₃H₆
State the colour change in the reaction of an alkene with bromine water
Orange to colourless
State the colour change when an alkane is mixed with bromine water
No change
What is produced when an alkene reacts with bromine?
A dibromoalkane
What two things can be added together to produce a dibromoalkane?
An alkene and bromine
What type of reaction takes place when bromine reacts with an alkene?
Addition
When bromine is added, what happens to an alkane?
Nothing (the sample remains orange)
When bromine is added, what happens to an alkene?
The sample turns from orange to colourless.
Bromine is added to a sample of an alkane and also to a sample of an alkene. Describe the result of each.
With the alkane, no change (stays brown). With the alkene, changes from brown to colourless
What is used to test if something is an alkane or and alkene?
Bromine water
Describe, in terms of structure and bonding, what happens when ethene molecules are converted into poly(ethene)
One bond in the double bond breaks. Monomers join together to form a long chain. Polymer contains only single bonds
Explain what is a monomer
Monomers are the many small molecules (such as ethene) which add together to make a polymer
Explain what is an addition polymer
An addition polymer is large molecule made by adding many small molecules (each containing a double bond) to form one much larger molecule
What is the process of joining monomers together called?
Polymerisation
Draw the equation to show the formation of poly(ethene)
Draw the equation to show the formation of poly(propene)
Draw the repeating unit for poly(but-1-ene)
Draw the repeating unit for poly(but-2-ene)
Draw the repeating unit for poly(chloroethene)
Draw the repeating unit for poly(ethene)
Draw the repeating unit for poly(propene)
Draw the displayed formula of the monomer used to make poly(but-1-ene)
Draw the displayed formula of the monomer used to make poly(but-2-ene)
Draw the displayed formula of the monomer used to make poly(ethene)
Draw the displayed formula of the monomer used to make poly(propene)
Explain why addition polymers are hard to dispose of
They are inert as they have strong C-C bonds. This makes them non-biodegradeable.
What is meant by the term biodegradable?
The break down of a substance by microorganisms
Draw the displayed formula for 2,2-dimethyl hexane
Draw the displayed formula for 2,3-dimethyl hexane
Draw the displayed formula for 2-methyl hexane
Draw the displayed formula for 4-ethyl octane
Draw the displayed formula for 4-methylpent-2-ene
Of which homologous series is >C=C< (a carbon-to-carbon double bond) the functional group?
Alkenes
What is the functional group of an alkene?
>C=C< (a carbon-to-carbon double bond)
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