Below are the IR spectra of two plastics (A and B); one is PETE, the other is low density polyethene (LDPE).

Deduce, giving your reasons, the identity and resin identification code (RIC) of A and B using sections 26 and 30 of the data booklet.

Describe the difference in their structures.

Explain why the difference in their structures affects their melting points.

A RIC: 1 AND B RIC: 4

ALTERNATIVE 1:
«only» PETE contains carbonyl/C=O/ester/COO groups
carbonyl groups absorb at 1700–1750 «cm^–1»

ALTERNATIVE 2:
LDPE contains more C–H bonds «than PETE»
C–H bonds absorb at 2850–3090 «cm^–1»

For either, accept specific frequencies in these ranges (eg 1735 «cm^–1» or 2900 «cm^–1»).

[3 marks]

HDPE less branched
OR
LDPE more branched

Accept “no branching in HDPE AND branching in LDPE”.

[1 mark]

HDPE «polymer» chains/molecules can pack together more closely «than LDPE chains»
OR
HDPE «polymer» chains/molecules have a higher contact surface area «than LDPE chains»

stronger intermolecular/dispersion/London/van der Waals’ forces in HDPE AND higher melting point

Accept converse arguments.

[2 marks]

State the name of one functional group common to all three vitamins shown in section 35 of the data booklet.

Explain the biomagnification of the pesticide DDT.

Explain why maltose, C₁₂H₂₂O₁₁, is soluble in water.

hydroxyl ✔

NOTE: Accept “hydroxy” but not “hydroxide”.
Accept “alkenyl”.
Do not accept formula.

accumulates in fat/tissues/living organisms
OR
cannot be metabolized/does not break down «in living organisms»
OR
not excreted / excreted «very» slowly ✔

passes «unchanged» up the food chain
OR
increased concentration as one species feeds on another «up the food chain» ✔

NOTE: Accept “lipids” for “fat”.

«solubility depends on forming many» H-bonds with water ✔
maltose has many hydroxyl/OH/oxygen atom/O «and forms many H-bonds» ✔

NOTE: Reference to “with water” required.
Accept “hydroxy” for “hydroxyl” but not “hydroxide/OH^–”.
Reference to many/several OH groups/O atoms required for M2.

State the raw materials and source of energy used in the process described above.

The structures of two molecules, X and Y, are shown below.

(i) Justify why both these molecules are carbohydrates.

(ii) Distinguish between these molecules in terms of their functional groups.

Amylose is an unbranched polysaccharide composed of repeating units of glucose.

(i) Draw the structure of the repeating unit of amylose. Use section 34 of the data booklet.

(ii) Amylose is a major component of starch. Corn starch can be used to make replacements for plastics derived from oil, especially for packaging. Discuss one potential advantage and one disadvantage of this use of starch.

CO₂ AND H₂O AND sun

Accept names.
Accept “sunlight/light/photons” instead of “sun”.

i

both have formula C_x(H₂O)_y
OR
both contain several OH/hydroxyl «groups» AND a C=O/carbonyl «group»

Accept “both have the formula C_nH_2nO_n /empirical formula CH₂O” but do not accept “both have same molecular formula/have formula C₃H₆O₃”.

Accept “aldehyde or ketone” for “carbonyl”.

ii

Accept “alkyl” for “R”.
Accept “X: aldose/aldehyde AND Y: ketose/ketone”.
Accept “CO” for “C=O”.

i

continuation bonds AND open O on either but not both ends

Brackets are not necessary for the mark.
Do not accept β-isomer.
Mark may be awarded if a polymer is shown but with the repeating unit clearly identified.
3-D representation is not required.

ii

Advantage:
Any one of:

biodegradable / break down naturally/by bacteria

Do not accept just “decompose easily”.

compostable

does not contribute to land-fill

renewable/sustainable resource

starch grains swell AND help break up plastic

lower greenhouse gas emissions

uses less fossil fuels than traditional plastics

less energy needed for production

Disadvantage:
Any one of:

land use «affects biodiversity/loss of habitat»

growing corn for plastics instead of food

«starch» breakdown can increase acidity of soil/compost

«starch» breakdown can produce methane «especially when buried»

sensitive to moisture/bacteria/acidic foods

«bioplastics sometimes» degrade quickly/before end of use

cannot be reused

poor mechanical strength

eutrophication

increased use of fertilizers/pesticides/phosphorus/nitrogen «has negative environmental effects»

Ignore any reference to cost.

Accept “prone to site explosions/fires” or “low heat resistance” for disadvantage.

Only award [1 max] if the same example is used for the advantage and disadvantage.

Identify the functional groups which are present in only one structure of glucose.

Sucrose is a disaccharide formed from $\alpha$-glucose and β-fructose.

Deduce the structural formula of sucrose.

Starch is a constituent of many plastics. Suggest one reason for including starch in plastics.

Suggest one of the challenges scientists face when scaling up the synthesis of a new compound.

Only in straight chain form:
carbonyl
OR
aldehyde

Only in ring structure:
hemiacetal

Accept functional group abbreviations (eg, CHO etc.). 

Accept “ether”.

[2 marks]

correct link between the two monosaccharides

Correct 1,4 beta link AND all bonds on the 2 carbons in the link required for mark.

Ignore any errors in the rest of the structure.

Penalize extra atoms on carbons in link.

[1 mark]

plastic «more» biodegradable/degrades into nontoxic products
OR
plastic can be produced using green technology/renewable resource
OR
reduces fossil fuel use/petrochemicals
OR
easily plasticized
OR
used to form thermoplasts

[1 mark]

minimize «negative» impact on environment
OR
minimize waste produced
OR
consider atom economy
OR
efficiency of synthetic process
OR
problems of side reactions/lower yields
OR
control temperature «inside large reactors»
OR
availability of starting/raw materials
OR
minimize energy costs
OR
value for money/cost effectiveness/cost of production

[1 mark]

Zanamivir must be taken by inhalation, not orally. Deduce what this suggests about the bioavailability of zanamivir if taken orally.

Oseltamivir does not possess the carboxyl group needed for activity until it is chemically changed in the body. Deduce the name of the functional group in oseltamivir which changes into a carboxyl group in the body. Use section 37 of the data booklet.

The synthesis of oseltamivir is dependent on a supply of the precursor shikimic acid, which is available only in low yield from certain plants, notably Chinese star anise. State one alternative green chemistry source of shikimic acid.

«oral bioavailability is» low
OR
drug is broken down/pH too low/unable to be absorbed from gut
OR
only a small proportion of the drug «taken by mouth» reaches the target organ

ethoxycarbonyl/carbonyl attached to oxygen

Accept “ester”.

Any one of:

fermentation
OR
microbial production

genetically engineered bacteria/E.coli

sweetgum «seeds/leaves/bark»
OR
pine/fir/spruce tree «needles»
OR
Ginkgo biloba

Accept other specific examples of more plentiful plant sources.

State two reagents required to convert vegetable oil to biodiesel.

Deduce the formula of the biodiesel formed when the vegetable oil shown is reacted with the reagents in (a).

Explain, in terms of the molecular structure, the critical difference in properties that makes biodiesel a more suitable liquid fuel than vegetable oil.

Determine the specific energy, in kJ$$g⁻¹, and energy density, in kJ$$cm⁻³, of a particular biodiesel using the following data and section 1 of the data booklet.

Density = 0.850 g$$cm⁻³; Molar mass = 299 g$$mol⁻¹;

Enthalpy of combustion = 12.0 MJ$$mol⁻¹.

methanol
OR
ethanol

strong acid
OR
strong base

Accept “alcohol”.

Accept any specific strong acid or strong base other than HNO₃/nitric acid.

[3 marks]

CH₃(CH₂)₁₆COOCH₃ / CH₃OCO(CH₂)₁₆CH₃
OR
CH₃(CH₂)₁₆COOC₂H₅ / C₂H₅OCO(CH₂)₁₆CH₃

Product must correspond to alcohol chosen in (a), but award mark for either structure if neither given for (a).

[1 mark]

lower viscosity

weaker intermolecular/dispersion/London/van der Waals’ forces
OR
smaller/shorter molecules

Accept “lower molecular mass/M_r” or “lower number of electrons”.

Accept converse arguments.

[2 marks]

Specific energy: «$=\frac{12000\text{ kJ}\text{mo}{\text{l}}^{-1}}{299\text{ g}\text{mo}{\text{l}}^{-1}}$» = 40.1 «kJ g⁻¹»

Energy density: «= 40.1 kJ$$g⁻¹ x 0.850 g$$cm⁻³» = 34.1 «kJ$$cm⁻³»

Award [1] if both are in terms of a unit other than kJ (such as J or MJ).

[2 marks]

State the IUPAC name for leucine.

A mixture of amino acids is separated by gel electrophoresis at pH 6.0. The amino acids are then stained with ninhydrin.

(i) On the diagram below draw the relative positions of the following amino acids at the end of the process: Val, Asp, Lys and Thr.

(ii) Suggest why glycine and isoleucine separate slightly at pH 6.5.

Determine the number of different tripeptides that can be made from twenty different amino acids.

The fibrous protein keratin has a secondary structure with a helical arrangement.

(i) State the type of interaction responsible for holding the protein in this arrangement.

(ii) Identify the functional groups responsible for these interactions.

2-amino-4-methylpentanoic acid

Accept 4-methyl-2-aminopentanoic acid.

i

Lys on cathode side AND Asp on anode side
Val at origin AND Thr on anode side but closer to origin than Asp

Val and Thr need not overlap.
Accept any (reasonable) size and demarcation of position so long as position relative to origin is correct.
Accept crosses for spots.
Award [1 max] for any two correct.
Award [1 max] if net direction of spots is reversed.
Award [1 max] if the four points are in the correct order but not in a straight line.

ii

different sizes/molar masses/chain lengths «so move with different speeds»

«20³ =» 8000

i

hydrogen bonds

ii

carboxamide/amide/amido
OR
C=O AND N–H

Accept peptide.

Draw the structure of the dipeptide Asp–Phe using section 33 of the data booklet.

The isoelectric point of amino acids is the intermediate pH at which an amino acid is electrically neutral.

Suggest why Asp and Phe have different isoelectric points.

amide link (eg, CONH) ✔

correct order and structures of amino acids ✔

NOTE: Accept a skeletal formula or a full or condensed structural formula.
Accept zwitterion form of dipeptide.
Accept CO–NH but not CO–HN for amide link.

«Asp isoelectric point lower than Phe and » Phe has a neutral/hydrocarbon side chain ✔
Asp side chain contains −COOH/carboxyl ✔

NOTE: Award [1 max] for “Asp has two carboxyl/−COOH groups and Phe has one carboxyl/−COOH group”.
Accept “Asp has an acidic side chain” for M2

Write the equation for the complete combustion of ethanol.

Outline the evidence that relates global warming to increasing concentrations of greenhouse gases in the atmosphere.

Explain, including a suitable equation, why biofuels are considered to be carbon neutral.

State the type of reaction that occurs when ethanol reacts with vegetable oil to form biodiesel.

C₂H₅OH (l) + 3O₂ (g) → 2CO₂ (g) + 3H₂O (l) ✔

Any two of:
«showing strong» correlation between «atmospheric» CO₂ concentration/greenhouse gas concentration and average «global/surface/ocean» temperature ✔

lab evidence that greenhouse gases/CO₂ absorb(s) infrared radiation ✔

«advanced» computer modelling ✔

ice core data ✔

tree ring data ✔

ocean sediments / coral reefs / sedimentary rocks data ✔

NOTE: Do not accept “global warming” for “average temperature”.
Do not accept “traps/reflects heat” OR “thermal energy”.
Evidence must be outlined and connected to data.
Accept references to other valid greenhouse gases other than carbon dioxide/CO₂, such as methane/CH₄ or nitrous oxide/N₂O.

biofuel raw material/sugar/glucose formed by photosynthesis
OR
biofuel raw material/sugar/glucose uses up carbon dioxide during its formation
OR
biofuel from capturing gases due to decaying organic matter formed from photosynthesis ✔

6CO₂ (g) + 6H₂O (l) → C₆H₁₂O₆ (aq) + 6O₂ (g) ✔

NOTE: Accept arguments based on material coming from plant sources consuming carbon dioxide/carbon for M1.

transesterification
OR
«nucleophilic» substitution/S_N ✔

Suggest why a high-octane number fuel is preferable.

Reforming reactions are used to increase the octane number of a hydrocarbon fuel.

Suggest the structural formulas of two possible products of the reforming reaction of heptane, C₇H₁₆.

The ¹H NMR spectrum of one of the products has four signals. The integration trace shows a ratio of the areas under the signals of 9 : 3 : 2 : 2.

Deduce the structural formula of the product.

low knocking/auto-ignition
NOTE: Do not accept “pre-ignition”.
OR
more efficient fuel
NOTE: Accept “less CO₂ emissions since knocking engine uses more fuel «to produce the same power»”.
OR
high compression
OR
more power extracted
OR
more air going into engine / turbocharging
OR
less engine damage ✔

Any two of:

NOTE: Accept skeletal formulas or full or condensed structural formulas.
Accept any other branched cycloalkane that contains 7 carbons.
Do not accept any alkenes.
Penalise missing hydrogens or bond connectivities once only in Option C.
Accept hydrogen as the second product if the first product is toluene or a cycloalkane.

NOTE: Accept a skeletal formula or a full or condensed structural formula.
Penalise missing hydrogens or bond connectivities once only in Option C.

Calculate the energy released, in $\mathrm{kJ}$, from the complete combustion of $5.00 {\mathrm{dm}}^3$ of ethanol.

State a class of organic compounds found in gasoline.

Outline the advantages and disadvantages of using biodiesel instead of gasoline as fuel for a car. Exclude any discussion of cost.

A mixture of gasoline and ethanol is often used as a fuel. Suggest an advantage of such a mixture over the use of pure gasoline. Exclude any discussion of cost.

Contrast the molecular structures of biodiesel and the vegetable oil from which it is formed.

When combusted, all three fuels can release carbon dioxide, a greenhouse gas, as well as particulates. Contrast how carbon dioxide and particulates interact with sunlight.

Methane is another greenhouse gas. Contrast the reasons why methane and carbon dioxide are considered significant greenhouse gases.

Suggest a wavenumber absorbed by methane gas.

$«21 200 \mathrm{kJ} {\mathrm{dm}}^{-3}\times 5.00 {\mathrm{dm}}^3=»106000/1.06\times {10}^5«\mathrm{kJ}»$ ✔

alkane
OR
cycloalkane
OR
arene ✔

Accept “alkene”.
Do not accept just “hydrocarbon”, since given in stem.
Do not accept “benzene/aromatic” for “arene”.

Advantages: [2 max]

renewable ✔

uses up waste «such as used cooking oil» ✔

lower carbon footprint/carbon neutral ✔

higher flashpoint ✔

produces less ${\mathrm{SO}}_{\mathrm{x}}$/${\mathrm{SO}}_2$
OR
less polluting emissions ✔

has lubricating properties
OR
preserves/increases lifespan of engine ✔

increases the life of the catalytic converter ✔

eliminates dependence on foreign suppliers ✔

does not require pipelines/infrastructure «to produce» ✔

relatively less destruction of habitat compared to obtaining petrochemicals ✔

Accept “higher energy density” OR “biodegradable” for advantage.

Disadvantages: [2 max]

needs conversion/transesterification ✔

takes time to produce/grow plants ✔

takes up land
OR
deforestation ✔

fertilizers/pesticides/phosphates/nitrates «used in production of crops» have negative environmental effects ✔

biodiversity affected
OR
loss of habitats «due to energy crop plantations» ✔

cannot be used at low temperatures ✔

variable quality «in production» ✔

high viscosity/can clog/damage engines ✔

Accept “lower specific energy” as disadvantage.

Do not accept “lower octane number” as disadvantage”.

Any one:

uses up fossil fuels more slowly ✔

lower carbon footprint/CO2 emissions ✔

undergoes more complete combustion ✔

produces fewer particulates ✔

higher octane number/rating
OR
less knocking ✔

prevents fuel injection system build up
OR
helps keep engine clean ✔

Accept an example of a suitable advantage even if repeated from 9c.

Any two:
biodiesel has smaller molecules/single «hydrocarbon» chain AND oil has larger molecules/multiple «hydrocarbon» chains ✔

biodiesel is methyl/ethyl ester AND oil has «backbone of» glycerol joined to fatty acids ✔

biodiesel contains one ester group AND oil contains three ester groups ✔

Do not accept properties such as “less viscous” or “lower ignition point”.

carbon dioxide allows sunlight/short wavelength radiation to pass through AND particulates reflect/scatter/absorb sunlight ✔

Accept “particulates reflect/scatter/absorb sunlight AND carbon dioxide does not”.
Accept “$C{O}_{\mathit{2}}$ absorbs $IR$ «radiation» AND particulates reflect/scatter/absorb sunlight”.

Do not accept “traps” for “absorbs”.

carbon dioxide is highly/more abundant «in the atmosphere» ✔

methane is more effective/potent «as a greenhouse gas»
OR
methane/better/more effective at absorbing $\mathrm{IR}$ «radiation»
OR
methane has greater greenhouse factor
OR
methane has greater global warming potential/GWP✔

Accept “carbon dioxide contributes more to global warming” for M1.

any value or range within $2850–3090«{\mathrm{cm}}^{-1}»$ ✔

Even rather weak candidates answered this one correctly.

Most candidates answered alkanes with a lower number stating hydrocarbons or benzene and therefore lost the mark. 

There were many good answers, but few candidates fully scored. Higher energy density and lower specific energy were quite common, and so references to damaging engines. Many students spent more time explaining each advantage rather than simply outlining. There were fewer journalistic and generic answers for this type of question than in the past.

Another question where many candidates obtained the mark. In quite a few cases students repeated the argument for (c) and this allowed them to get two points for the same answer.

Quite disappointing with few candidates producing answers that showed deep understanding. Answers such as less viscous or lower ignition point were common. This question specifically asks for contrasts in the structures not the properties of the compounds. Students need to be reminded that a contrast statement requires something about each substance.

Showed a wide variety of answers but is was worrying that many students limited to explain the greenhouse effect. There were many responses that did not answer the question or only gave a response for one of the 2 substances.

We received many good answers, but it was worrying the number of students that still provided general and shallow comments. Of the 3 contrast question this had the best response.

Many good answers with some students losing the mark as didn't read or understand the question correctly and provided answers in terms of wavelengths.

State the names of two functional groups present in all three molecules, using section 37 of the data booklet.

Explain why diamorphine has greater potency than morphine.

Any two of:
benzene/aromatic ring ✔
«tertiary» amino «group» ✔
ethenylene/1,2-ethenediyl «group» ✔
ether «group» ✔

NOTE: Accept “phenyl” for “benzene ring” although there are no phenyl groups as the benzene ring in this compound is a part of a polycyclic structure.
Do not accept “arene” or “benzene” alone.
Accept “amine” for “amino «group»”.
Accept “alkenyl/alkene/vinylene” for ethenylene/1,2-ethenediyl «group».

Any three of:
morphine has «two» hydroxyl «groups» AND diamorphine has «two» ester/ethanoate/acetate «groups» ✔

NOTE: Accept “heroin” for “diamorphine”.
Accept formulas.
Accept “hydroxy” for “hydroxyl” but not “hydroxide”.
Accept “acyl” for “ester «groups»”.

morphine is more polar than diamorphine
OR
groups in morphine are replaced with less polar/non-polar groups in diamorphine ✔

NOTE: Do not accept just “diamorphine is non-polar” for M2.

morphine is «more» soluble in blood «plasma»
NOTE: Accept “water” for “blood”.
OR
diamorphine is «more» soluble in lipids
NOTE: Accept “fats” for “lipid”.
OR
diamorphine is more soluble in non-polar environment of CNS/central nervous system than morphine ✔

diamorphine crosses the blood–brain barrier/BBB «easily» ✔

Describe two differences, other than the number of atoms, between the models of ethane and ethene constructed from the kit shown.

The above ball and stick model is a substituted pyridine molecule (made of carbon, hydrogen, nitrogen, bromine and chlorine atoms). All atoms are shown and represented according to their relative atomic size.

Label each ball in the diagram, excluding hydrogens, as a carbon, C, nitrogen, N, bromine, Br, or chlorine, Cl.

Suggest one advantage of using a computer generated molecular model compared to a ball and stick 3-D model.

Pyridine, like benzene, is an aromatic compound.

Outline what is meant by an aromatic compound.

Any two of:

Ethene: «carbon–carbon» double bond AND Ethane: «carbon–carbon» single bond

ethene has a shorter carbon–carbon bond «than ethane»

Ethene: planar/two-dimensional/2-D AND Ethane: tetrahedral «carbons»/three-dimensional/3-D

OR

Ethene: each carbon surrounded by three electron domains AND Ethane: each carbon surrounded by four electron domains

OR

different molecular geometries/shapes

rotation about carbon–carbon inhibited/blocked in ethene AND not in ethane

«H–C–C/H–C–H» bond angles different

OR

Ethene: «bond angles approximately» 120° AND Ethane: 109.5/109°

Do not accept “different number of atoms/hydrogens/bonds” etc.

Accept “Ethene: unsaturated AND Ethane: saturated” OR “Ethene: has a double bond AND Ethane: does not” OR “Ethene: two flexible bonds between carbon atoms AND Ethane: one”.

Accept any reasonable physical description of the two different molecular models based on a variety of kits for M1.

For ethene, accept any bond angle in the range 117–122°.

Award [2] if any two of the concepts listed are shown in a correctly labelled or annotated diagram.

Award [1 max] for two correct statements for either molecule but with no comparison given to the other.

Award [1 max] for suitable unlabeled diagrams of both compounds.

[2 marks]

6 carbon atoms labelled in correct positions

both nitrogen atoms labelled in correct positions

bromine AND chlorine atoms labelled in correct positions

[3 marks]

accurate bond angles/lengths can be measured

OR

«using mathematical functions» can calculate expected shapes based on energy minimizations

OR

better visualization of possible bond rotations/conformation/modes of vibration

OR

can visualize macromolecules/proteins/DNA

OR

hydrogen bonding «networks» can be generated/allows intermolecular forces «of attraction» to be simulated

OR

more variety of visualization representations/can observe space filling

OR

can produce an electron density map/electrostatic potential map

OR

once model is generated file can be saved for future use/computer models can be shared globally by scientists

OR

helps design molecules of biological significance/assists in drug design «using libraries»

OR

can predict molecular interactions with solvents/can predict physical properties/can predict spectral data/can examine crystal structures

OR

«often» easier to construct/modify «model»

Accept “precise” for “accurate”.

Accept “computer generated structural representation is normally what is expected in order to be published «in a scientific journal»”.

Accept “easier to see different sizes of atoms/atomic radii”.

[1 mark]

bonds within ring have resonance

OR

contains delocalized «conjugated pi» electrons in ring

There must be reference to a ring or cyclic structure.

Accept “alternating single and double bonds in a ring”.

Accept “ring which shows resonance/delocalization”.

Accept “follows Hückel/4n +2 rule”.

Do not accept “contains one or more benzene rings”.

[1 mark]

The iodine number is the number of grams of iodine which reacts with 100 g of fat. Calculate the iodine number of oleic acid.

State one impact on health of the increase in LDL cholesterol concentration in blood.

Explain why stearic acid has a higher melting point than oleic acid.

State one similarity and one difference in composition between phospholipids and triglycerides.

Similarity:

Difference:

Identify a reagent that hydrolyses triglycerides.

«one C=C bond»
«1 mole iodine : 1 mole oleic acid»

« $\frac{100\times 253.80}{282.46}$ =» 89.85 «g of I₂» ✔

NOTE: Accept “90 «g of I₂»”.

atherosclerosis/cholesterol deposition «in artery walls»/increases risk of heart attack/stroke/cardiovascular disease/CHD ✔

NOTE: Accept “arteries become blocked/walls become thicker”, “increases blood pressure”, OR “blood clots”.
Do not accept “high cholesterol” OR "obesity"

no kinks in chain/more regular structure
OR
straight chain
OR
no C=C/carbon to carbon double bonds
OR
saturated
OR
chains pack more closely together ✔

NOTE: Accept “greater surface area/electron density” for M1.

stronger London/dispersion/instantaneous induced dipole-induced dipole forces «between molecules» ✔

NOTE: Accept “stronger intermolecular/van der Waals’/vdW forces” for M2.

Similarity:

«derived from» propane-1,2,3-triol/glycerol/glycerin/glycerine

OR
«derived from» at least two fatty acids
OR
contains ester linkages
OR
long carbon chains ✔

NOTE: Do not accept “two fatty acids as both a similarity and a difference”.
Do not accept just “hydrocarbon/carbon chains”.

Difference:

phospholipids contain two fatty acids «condensed onto glycerol» AND triglycerides three
OR
phospholipids contain phosphate/phosphato «group»/residue of phosphoric acid AND triglycerides do not ✔

NOTE: Accept “phospholipids contain phosphorus AND triglycerides do not".
Accept “phospholipids are amphiphilic AND triglycerides are not” OR “phospholipids have hydrophobic tails and hydrophilic heads AND triglycerides do not”.

«concentrated» NaOH (aq)/sodium hydroxide
OR
«concentrated» HCl (aq)/hydrochloric acid
OR
enzymes/lipases ✔

NOTE: Accept other strong acids or bases.

State and explain the further work students need to carry out in trial 2 before they can process the results alongside trial 1.

In trial 3, the students noticed that after heating, the crucible had turned black on the outside. Suggest what may have caused this, and how this might affect the calculated value for x in the hydrated salt.

List two assumptions made in this experiment.

repeat steps 3 and 4
OR
repeat step 5
OR
conduct a third heating
OR
«re»heat AND «re»weigh  

water still present
OR
need two consistent readings
OR
heat to constant mass

Accept “ensure even/strong heating” for M1.
Do not accept “cleaning/washing the crucible”.

soot/carbon deposited
OR
incomplete combustion
OR
air hole of Bunsen burner closed/not fully open

Accept “using a yellow «Bunsen burner» flame” for M1.

«value of x» lower

Only award M2 if M1 correct.

all mass loss is due to water loss

all the water «of crystallization» is lost

crucible does not absorb/lose water

crystal/BaCl₂ does not decompose/hydrolyse/oxidize/react with oxygen/air «when heated»

Accept “no loss of crystals/BaCl₂ occurs”, “no impurities in the «weighed hydrated» salt”, “reaction goes to completion”, “heat was consistent/strong”, “crystal/BaCl₂ does not absorb water during cooling”, “balance has been calibrated” or “crucible was clean at the start”.

Do not accept ”heat loss to surroundings” or “no carbon deposited on crucible”.

Reference to defects in apparatus not accepted.

Do not penalize if BaCl₂.xH₂O is used for BaCl₂.

Name two functional groups that both zanamivir and oseltamivir contain.

Explain how zanamivir works as a preventative agent against flu viruses.

Circle the side-chain in penicillin on the structure below.

Explain, with reference to the action of penicillin, why new penicillins with different side-chains need to be produced.

State and explain the relative solubility of codeine in water compared to morphine and diamorphine.

State the natural source from which codeine, morphine and diamorphine are obtained.

Any two:
«secondary» carboxamide/amido ✔
ether ✔
carbonyl ✔

Accept amide
Accept amino/amine.
Accept alkenyl/alkene.

Do not accept formula.

«drug» blocks/inhibits «viral» enzyme/neuraminidase/$\mathrm{NA}$ «activity» ✔
prevents virus from leaving/escaping host cells «thus cannot infect other cells» ✔

Do not accept other anti-viral methods (as question is specific to Zanamivir).

 ✔

Accept a circle that does not surround the amido group.

Do not accept a circle that only surrounds the phenol group.

bacterial resistance «to older penicillins/antibiotics» ✔

prevent penicillinase/beta-lactamase/enzyme in bacterium to deactivate/open penicillin/beta-lactam ring ✔

Accept “antibiotic resistant bacteria” but not “antibiotic resistance” for M1.
Accept “reduce allergic reactions from from penicillin” for M2.
Award [1 max] for “increased efficiency” OR “increased stability in GIT”.
Do not accept “bacteria develop tolerance”.

codeine less soluble «in water» than morphine AND more soluble than diamorphine
OR
morphine > codeine > diamorphine «in terms of solubility in water» ✔

more/stronger/greater hydrogen/H bonding «due to more hydroxyl groups leads to greater solubility» ✔

opium poppy/plants/seeds ✔

Accept “poppy” OR “opioid”.

Most students scored both marks here. Some students with incorrect answers gave carboxylic acid/carboxyl, benzene/arene, and ester.

Even when a relevant number of students obtained at least one mark, the quality of the answers was in general low and many evidenced very shallow understanding just repeating information

Many students scored here but a relevant percentage didn't include the amide group. Quite a few students did not know where the side chain is and circled other parts of the molecule.

Many good answers for M1 but only stronger students managed to score the second one. The answers evidenced again shallow understanding that may result from independent learning. Many students gave answers related to how penicillin causes bacteria to burst which is not related to this question. Once again it shows students perhaps memorizing answers without a true understanding of concepts.

M1 was correctly presented but most students focused on the polarity of the molecules and presented long arguments where intermolecular forces were ignored. The concept of water solubility and hydrogen bonding was largely ignored.

Mostly well answered. Student who missed this question were clearly guessing with other natural products presented with the Option D material.

Determine the empirical formula of linoleic acid.

The empirical formula of fructose is CH₂O. Suggest why linoleic acid releases more energy per gram than fructose.

State the type of reaction occurring during the titration.

Calculate the volume of iodine solution used to reach the end-point. 

Outline the importance of linoleic acid for human health.

C₉H₁₆O

ratio of oxygen to carbon in linoleic acid lower

OR

linoleic acid less oxidized

OR

linoleic acid more reduced

Accept “«average» oxidation state of carbon in linoleic acid is lower”.

«electrophilic» addition/A_E

OR

oxidation–reduction/redox

«$\frac{1.24\text{g}}{280.50\text{g}\text{mo}{\text{l}}^{-1}}$ =» 0.00442 «mol»

0.00884 mol of C=C

OR

ratio of linoleic acid : iodine = 1:2

«volume of I₂ solution = $\frac{0.00884\text{mol}}{0.300\text{mol}\text{d}{\text{m}}^{-3}}$ =» 0.0295 «dm³» / 29.5 «cm³»

Award [3] for correct final answer.

Any two of:

increases «ratio of» HDL «to LDL» cholesterol

OR

decreases LDL cholesterol «level»

removes plaque from/unblocks arteries

OR

decreases risk of heart disease

decreases risk of stroke «in the brain»

Accept "essential fatty acid".

Do not accept “bad cholesterol” for “LDL cholesterol” OR “good cholesterol” for “HDL cholesterol”.

Do not accept general answers such as “source of energy” OR “forms triglycerides” OR “regulates permeability of cell membranes” etc.

[Max 2 Marks]

State the name of the functional group which allows the molecule to be responsive to applied electric fields.

Explain the effects of very low and high temperatures on the liquid-crystal behaviour of this molecule.

Low temperature: 

High temperature:

nitrile  [✔]

Note: Accept “cyano".

Low temperature:
intermolecular forces prevent molecules moving AND solid/«normal» crystal formation  [✔]

High temperature:
«above a critical temperature» disrupts alignment of molecules AND behaves as fluid/liquid  [✔]

Note: Accept “weak intermolecular forces break AND behaves as fluid/liquid”.

A few students correctly named the nitrile group as being the one responsible for the polarity of the liquid crystal molecule.

Very poorly answered with candidates failing to link the change in liquid crystal properties to changes in molecular motion.

Compare and contrast the functional groups present in methadone and diamorphine (heroin), giving their names. Use section 37 of the data booklet.

Methadone is sometimes used to help reduce withdrawal symptoms in the treatment of heroin addiction. Outline one withdrawal symptom that an addict may experience.

Similarity:

both contain «at least one» benzene/aromatic ring
OR
both contain amino «group»  

Difference:

diamorphine has one benzene/aromatic ring AND methadone has two phenyl «groups»
OR
diamorphine has one vinylene/ethenylene/1,2-ethenediyl «group» AND methadone has no vinylene/ethenylene/1,2-ethenediyl «group» 
OR
diamorphine has one ether «group» AND methadone has no ether «group»
OR
diamorphine has «two» ethanoate/acetate «groups» AND methadone has no ethanoate/acetate «groups»

Accept “both contain carbonyl «groups»”.
Accept “amine” for “amino «group»”.
Accept “phenyl” for “benzene ring” in M1 and M2 although there are no phenyl groups in diamorphine, as the benzene ring in this compound is a part of a polycyclic structure.
Do not accept “arene” or “benzene” alone in M1 and M2.
Accept “alkenyl/alkene” for “vinylene/ethenylene/1,2-ethenediyl” and “ester” for “ethanoate/acetate”.
Accept “methadone has a ketone/carbonyl AND diamorphine does not/has an ester/ethanoate/acetate”.
Accept “diamorphine is a heterocycle/heterocyclic compound AND methadone is not a heterocycle/heterocyclic compound”.

feeling depressed/anxious/irritable
OR
craving for opioids/heroin
OR
experience fever/cold sweats/nausea/vomiting/insomnia/muscle pain/cramps/diarrhea/increased rate of respiration/increased heartbeat/lacrimation

Accept listed symptoms (eg, depression, anxiety, fever etc.).
Some of the most common symptoms are listed here – there may be other valid ones. Accept “headaches”.