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STUDENT SUPPLEMENT

ISSUE MAY

STUDENT SUPPLEMENT MAY 2010 • VOLUME 47 • NUMBER 3

Maths required…Should HE chemistry insist on A-level mathematics?

Science educationReport fi nds pre-19 science education could be better

Modern Modern Modern analysis analysis analysis Developments in Developments in Developments in mass spectrometry mass spectrometry mass spectrometry

www.rsc.org/eic

ISSN 0013-1350

Small sea crustaceans – limnoriides or gribbles – have been munching their way through ship hulls and sea-side piers for centuries, wrecking havoc as they bore through the wooden structures. By studying the way the gribbles digest the wood, however, scientists at the UK’s Sustainable Bioenergy Centre at the Universities of York and Plymouth are hoping to fi nd an energy-effi cient route to biofuel production.

Biofuels have traditionally been made from carbohydrate-rich crops, such as corn and sugar beet. The carbohydrates are hydrolysed into sugars, which are then fermented (broken down) into alcohols and carbon dioxide. Such fuel crops compete with food crops for land use so biofuels that are not produced from edible material,

such as woody material from plants, are an attractive alternative.

Wood is made up of lignocellulose, ie energy-rich sugar polymers (cellulose and hemi-cellulose) surrounded by the highly branched polymer, lignin. The resulting structure is tough and rigid, making it diffi cult to access the cellulose for biofuel production. Current methods are energy-intensive, requiring high temperature and pressure. In contrast, gribbles are able to break down lignin in a rather neat and simple way.

In a paper published in the Proceedings of the National Academy of Science USA, Professor Simon McQueen and his team found that

gribbles break down wood using enzymes they produce themselves. This is diff erent to termites and other wood-eating animals such as cattle, which have a host of microbes in their digestive tract to do the job for them. The gribbles digestive tract, the scientists say, is unique in that it is eff ectively a sterile environment, which off ers an opportunity for identifying the specifi c enzymes and reaction conditions for the degradation of lignocellulose.

The researchers are currently analysing the gribble gut enzymes to fi nd out how they work and whether they can recreate the gribbles’ secret on an industrial scale.

BORING GRIBBLESPET wasteChemists recycle millions of plastic water bottles

A day in the life of…Jessica Kershaw,Trainee patent attorney

On-screenchemistryAre there valuable fuel reserves on the Moon?

BackyardchemistryThe colour of money

Plus…Prize puzzles

Infochem is a supplement to Education in Chemistry and is published bi-monthly by the Royal Society of Chemistry, Burlington House, Piccadilly, London W1J 0BA, UK. 020-7437 8656, e-mail: [email protected] www.rsc.org/Education/EiC/index.asp

© The Royal Society of Chemistry, 2010Published in January and alternate months. ISSN: 1752-0533

IN THIS ISSUE

Editor Kathryn Roberts

Assistant editor Laura Howes

Design and layout Carolyn Knighton

1

Did you know?RSC ChemNet’s Meet the Universities event is approaching, where you get the chance to meet academics from diff erent universities off ering chemical science degrees and fi nd out what’s on off er. The event will be held at the RSC’s Chemistry Centre in London on Saturday 3rd July. Visit www.rsc.org/mtu for more information.

A feast fi t for gribbles…

InfoChem MAY_2010.indd 1 13/04/2010 16:49:30

2 You may copy this page for use within schools

ISSUE 122 MAY 2010

Recycling plastic bottles

M ost clear plastic bottles are made from the polyester, poly(ethene terephthalate), or PET

(1). Triangular arrows surrounding the number 1 stamped on the bottle identify the plastic as PET. High-density poly(ethene), HDPE, is used to make milk bottles (number 2 in the recycling symbol). The caps and rings that keep the bottles’ content fresh or fizzy are made from poly(propene), PP. Like all plastics, PET, HDPE and PP are polymers – their molecules are long chains made from repeating units of smaller molecules. In the

case of PET the repeating unit is ethene terephthalate; in HDPE it is ethene (2), and in PP is propene (3).

A large amount of plastic waste is shipped abroad, often to Asia, where it is processed to be re-used in low-grade products like fibres for clothing, carpets or plastic strapping. Some of it, PET in particular, is made back into bottles at plants like Closed Loop Recycling (CLR), in Dagenham, Essex.

Used plastic bottles arrive at CLR in bales weighing about 500 kg and containing around 12 500 plastic bottles, along with items like carrier bags, yoghurt pots, and cans. The contents of the bales have to be sorted

because failure to separate the plastics will cause problems with the end product.

Nick Cliffe, marketing manager at CLR, singles out polyvinyl chloride, PVC, poly(chloroethene) (4) as the main ‘headache substance’ for CLR. PVC is commonly used in blister packaging for batteries as well as in plastic pipes, and as Cliffe says ‘has similar properties and looks like PET to the naked eye, but it blackens at 200 °C’. A tiny black speck in a recycled PET bottle, he explains, will weaken it so much it could explode when filled with fizzy drink, and just one PVC bottle in a batch of 10 000 PET bottles could ruin the entire batch. Separating all the different types of

Recycling plastic bottles prevents the plastic from going to landfill, saves energy and reduces our dependency on oil. But what do we have to do to put the bottle back on the supermarket shelf?

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3You may copy this page for use within schools

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fl avouring limonene, evaporate in the heat. Other contaminants, mostly dried remnants of the original drink, are also removed by washing. The PET fl akes that are left behind are clean enough to be melted down and made into new bottles.

A similar process to hydrolysis, ie methanolysis, is used to depolymerise PET into its core ingredients by the Eastman Chemical Company in the US. Methanol at temperatures above 250 °C attacks the ester linkages in the PET chain, breaking it down into dimethyl terephthalate and ethane-1,2-diol. A catalyst such as sodium methoxide can be used to speed the reaction up. The product, dimethyl terephthalate, can be repolymerised or hydrolysed to form terephthalic acid.

Mitsubishi Heavy Industries in Japan has

� e journ� begins…plastic is a challenge, but CLR has found that the solution lies in exploiting the chemical diff erences between the diff erent polymers.

‘Diff erent polymers refl ect and absorb diff erent amounts of light, and at diff erent wavelengths, especially in the near infrared’ explains Cliff e. ‘As the bottles pass by a series of “optical sorters”, ie bright bulbs emitting in the near infrared, diff erent polymers trigger a jet of air, which blows the bottle down a chute. This is also useful for removing coloured PET, which can’t be included in the fi nal product but can be recycled for uses where colour is not so important’.

Some bottles can make it past the optical sorters so another diff erence is exploited once the polymers have been shredded ready for processing: PET is more dense than water, while polyalkenes, like HDPE and PP, are less dense. So when the fl ake mixture is dumped into a tank of water, the PET fl akes sink to the bottom, while the fl oating HDPE and PP can be skimmed off the surface. Recovered PP is recycled for low-grade uses.

A fi nal check of the PET fl akes is done using Raman spectroscopy. In this process each fl ake is hit with a laser, causing the electrons in the fl ake material to absorb the laser energy and jump into a high-energy state. As the electrons drop back down to their original energy state, they release the absorbed energy as light. The range of wavelengths of light emitted (the spectrum) depends on the chemical structure of the compounds

containing the electrons. Thus individual atoms and bonds can be identifi ed. CLR uses Raman because the emitted light is a ‘unique molecular fi ngerprint’ of whatever is in the fl ake. When the Raman spectrum of a rogue fl ake or contaminant is detected it is ejected from the mix with a jet of air.

C If the PET bottle is going to be re-used for food or drinks packaging it must have all contaminants removed. At CLR, this is done by stripping off a layer of plastic, a few micrometres thick, from the surface of the PET fl akes in a reaction that Cliff e describes as a ‘chemical peel’. In fact, the reaction is a depolymerisation: the reverse of the polymerisation reaction that originally formed the plastic.

Each PET fl ake is coated with a vaporised solution of sodium hydroxide. The coated fl akes are heated to 200°C in a rotating oven. At that temperature, the hydroxide ions attack the ester groups in the polymer chains nearest the fl ake surface. This hydrolysis reaction breaks up the PET chains into terephthalic acid and ethane-1,2-diol (ethylene glycol), the same two compounds which were originally used to make the polymer, see Scheme 1 (s1).

The terephthalic acid forms sodium terephthalate,with the sodium from sodium hydroxide. This salt is water soluble and can be washed away, along with the ethane-1,2-diol. Volatile organic contaminants, such as the CL

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ISSUE MAY

Few materials have the elasticity of natural rubber, which is obtained from the latex of the rubber tree, Hevea brasiliennis. Rubber is also waterproof and fl exible, two properties that were exploited by Charles Macintosh to produce the fi rst raincoats. A great idea but in practice they were a disaster. The rubber turned sticky in hot weather and brittle in the cold. The raw material needed to be chemically modifi ed to be of any use, and the man who solved the problem was the US inventor Charles Goodyear.

According to a recent biography, Nobel obsession by Charles Black (published by Hyperion), Goodyear was obsessed by rubber.

If you meet a man who has on an India rubber cap, stock, coat, vest, and shoes, with an India rubber money purse, without a cent in it, that is he.

From 1834 onwards Goodyear devoted his

time and money to making rubber into a useful product. He did hundreds of experiments, mixing almost everything with natural rubber to modify and improve its properties. The breakthrough came by chance, though the details are obscure and inconsistent since he never wrote down a full

account. In 1839, a sample of rubber mixed with sulfur fell or was thrown onto a hot stove and instead of melting or burning it changed into a dark leathery mass. Goodyear pursued this, doing many more experiments until he had a reliable process, and called the product ‘fi re-proof gum’. Now known as vulcanised rubber, after the Roman god of fi re, Vulcan, it is stretchy and waterproof, and doesn’t turn sticky when hot. Rubber, both natural and synthetic, fulfi lled its early promise as a ‘miracle substance’ thanks to Goodyear’s persistence and a prepared mind.

Rubber is made up of long polymer (poly(isoprene)) chains, which can move independently of each other. In vulcanisation, the sulfur atoms act as bridges (crosslinks) between the chains and stop the them from moving. This gives a less sticky substance with superior mechanical properties.

Peter Childs, University of Limerick, selects examples where chance led chemists to new and unexpected discoveries. In this issue: rubber

accidental discoveries:

developed a variation of this reaction that uses supercritical methanol (ie methanol which is heated at high pressure to beyond its boiling point). At these conditions the reaction is faster and does not require a catalyst.

Ethane-1,2-diol can be used instead of methanol to attack the PET ester linkages. This reaction (glycolysis), which also requires high temperatures and pressure and can be catalysed by a compound such as zinc acetate, forms bishydroxyethyl terephthalate and shorter PET segments called oligomers. These products can all be re-polymerised to make fresh PET.

George Roberts, professor of chemical and biomolecular engineering at North Carolina State University, US, has recently developed a method for reacting PET with ethane-1,2-diol in a large corkscrew-type chamber, allowing

the process to run continuously. As the extruder screw turns, it melts the PET, allowing it to react more rapidly with ethane-1,2-diol to form shorter PET oligomers. ‘Once we have these shorter segments, the viscosity of the material is signifi cantly reduced. We can take out any solid, liquid or vapour impurities and wind up with a material that can be put through a normal polymerisation process’, said Roberts. ‘We think it is more economical to make the oligomer because most polyester processes involve two stages, and the second stage starts with an oligomer.’

Natural, white, HDPE can also be turned back into a food-grade plastic containers. The bottles are heated to 120 °C at low pressure. When the plastic melts, the contaminating remnants of

the drink to simply evaporate. The molten plastic is then fi ltered through a fi ne mesh, cut into pellets and cooled, ready to be turned into new milk bottles.

So next time you drop your plastic water bottle in the recycling bin, think about the chemical journey it will take before it ends up as just another bottle.

Tom Westgate

Optical sorters

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In the fi lm Moon,1 the Earth’s resources of oil and coal have dwindled and nuclear fusion provides the power. The fuel is an isotope of He (3He: two protons and one neutron) which is mined on the Moon and then sent back to Earth. So is 3He fusion feasible and would it ever be worth going 250 000 miles to the Moon to get it?

The most obvious natural fusion process is that taking place within our Sun but this is not an easy process to replicate in the lab because of the very high temperatures needed to overcome the repulsion of the positive nuclei. Indeed there are other fusion reactions – eg the fusion of deuterium (2

1H, an isotope of hydrogen extractable from sea water) with 3He – that are preferable because they produce more energy.

32He + 21H 42He + 11P + neutrinos

+ 2.9 x 10–12 J (i)

Unfortunately 3He is scarce on Earth but the Moon may store useful quantities trapped in the dusty mantle covering the surface (the regolith). Roughly one tonne of 3He might be extracted from every 100 million tonnes of regolith.2 In the fi lm we see machines running along the surface of the moon scooping up the regolith and heating it up to remove and store the 3He gas. As everything is automated it only requires one person to oversee the plant. In the fi lm Sam (Sam Rockwell) plays the moody caretaker at the extraction plant. His job is to collect the 3He storage tanks from the automated collectors and send them back to Earth via small spaceships.

In the fi lm the cylindrical tanks look about 1 meter long (h = 1m) and about 25 cm wide

(d = 0.25 m). Modern cylinders can take pressures of about 300 bar (about 300 times the Earth’s atmospheric pressure) but if we estimate that in the future the tanks can withstand 1000 bar pressure, we can work out how much 3He is contained in one tank and what would it be worth.

The tank volume is V = πr2h = π(d/2)2 × h = π(0.125)2 x 1 = 0.05 m3 which at STP would be equivalent to 1000 × 0.05 = 50 m3 = 50 000 dm3 of 3He. Now 1 mole = 22.4 dm3 which means we have 2200 moles of 3He, amounting to 2200 × 3 = 6600 g = 6.6 kg of 3He per tank, equivalent to 2200 × 6.022 x 1023 = 1.32 × 1027 atoms per tank.

Equation (i) give us the energy per reaction, and a total energy of E = 2.9 10–12 × 1.32 x 1027 = 3.9 × 1015

J per tank (note: some energy may be lost via neutrinos). Now the current world power consumption is about 16 terawatts, which is 16 × 1012 J s–1 = 1.38 × 1018 J per day. On this basis the world would need about 400

tanks per day but according to one estimate only one full space shuttle load of 3He would be needed to provide the US’s yearly energy needs.3 One barrel ($80) of oil is equivalent to 6 × 109 J so (ignoring the deuterium costs) a single tank of 3He would be equivalent to 640 000 barrels, or about $50 million dollars worth!

It’s early days to know exactly what the technical challenges would be trying to automate such a process on the Moon. However, as resources get used up on Earth such a valuable fuel, even if it is on the Moon, would start to look attractive.

REFERENCES1. Moon, Sony Pictures Home Entertainment Inc. 2009.2. Wiki entry for 3He: http://en.wikipedia.org/wiki/Helium-33. The Artemis project: http://www.asi.org/adb/02/09

/he3-intro.html

Dr Jonathan Hare, The CSC Centre, chemistry department, University of Sussex, Brighton BN1 9ET (www.creative-science.org.uk/TV.html).

Jonathan Hare asks. . .MOON RAKER: could you harvest the Moon for energy and solve Earth’s looming crisis?

Could our future energy supply really lie in the Moon’s dusty mantle?


Issue MARCH Dr H a l S o S a bow Sk i p r e S e n t S e x p e r im e n t S yo u c a n D o o n yo u r own

IN THIS ISSUE: the change in your pocket


If you look through the changein your pocket, specifically the copper coins, you will notice that some are a bright, shiny orange colour, others are a much duller shade of brown. In this experiment we are going to restore your small dull change to brilliance using lemon juice or vinegar.

M You will need:

� small copper coins (well tarnished); � an egg cup; � lemon juice or white wine vinegar; � laboratory gloves (or Marigold-type rubber gloves);

� safety glasses.

MPour a little of the vinegar or lemon juice into the egg cup so that by propping one of the coins against the side, half the coin is immersed in the liquid and half isn’t. Leave for 10 minutes. Remove the coin and notice how the wet half is untarnished, shiny and orange.

T The tarnish on copper coins is caused by gradual oxidation of the copper by atmospheric oxygen. The resultant coating of copper oxide, CuO, is black, and so the thin oxide layer gradually darkens the orange colour of the copper coin to a darker brown.

Acids, such as citric acid in lemons or ethanoic acid in vinegar, react with the copper oxide: the Cu2+ ions dissolve in the aqueous phase and the oxygen reacts with the H+ of the acid to form water:

CuO + CH3COOH CH3(COO)2Cu + H2O

copper oxide + ethanoic acid copper ethanoate + water

The copper dissolving as copper ions as part of copper ethanoate in the solution can be seen by the gradual change in colour of the acid solution – from clear to a greenish colour. Crystals of solid copper ethanoate can be obtained by allowing the liquid in the egg cup to evaporate over a several days. These crystals should only be handled with gloves.

Rust on cars can be controlled by a similar reaction using phosphoric acid. Rust is iron(III) oxide, Fe2O3 which can be converted to the other form of oxide, iron(II) oxide, FeO. This is a black solid which doesn’t fl ake and spreads in the same way that rust does, thereby extending the useful life of the car.

H SYou should wear approved safety glasses since lemon juice and vinegar can cause eye irritation. You should also wear laboratory gloves or Marigold-type rubber gloves if/when handling residual copper ethanoate. The gloves should be disposed of after the activity and your hands washed immediately afterwards.

D Historically coinage was made of gold. Gold is a noble metal and the gold

doubloons, fl orins, ducats and krugerrands were (and still are) precious partly because they are made of a metal which doesn’t oxidise or tarnish. Lower value coins were made of less valuable metals such as copper, because if they were made of valuable metals the value of the metal would exceed the value of the coin.

As it happens, for a short time in 2006 the value of the copper in a pre-1992 2p coin, which contains 97 per cent copper, was 3p. A tonne of copper coins would consist of 145 000 2p coins or 290 000 1p coins, giving it a monetary value of £2900. But at that time a tonne of copper would fetch £4500 on the commodity market. The reason that we didn’t see an instant clutch of 2p millionaires is that it’s actually quite diffi cult to get 145 000 2p coins from the bank, and even if you could, it is an off ence to melt down the coins of the realm.


TRAINEE PATENT ATTORNEYJessica Kershaw

A …

Jessica Kershaw has spent the past four months as a trainee patent attorney for Carpmaels & Ransford, London. She talks to Tom Westgate about her typical day.

J� ica Kershaw

Issue MARCH Dr H a l S o S a bowS k i p r e S e n t S e x p e r im e n t S yo u c a n D o o n yo u r own


Carpmaels & Ransford is a fi rm specialising in all areas of intellectual property. As a trainee patent attorney, Jessica works to secure the patent rights of her clients for their inventions, ensuring no-one else can make money from them.

M-Jessica’s chemistry background means she often works with clients from the pharmaceutical industry on patents for new drugs, new formulations, or new ways of manufacturing them, for example. But she could also be trying to secure patents for new materials or compositions for everyday products, like protective plastic or electrical conductors. She works for several diff erent clients at any one time, from multinational companies to small start-up companies linked to universities.

It can take up to fi ve years to secure a patent, and there are many steps to go through on the way. Jessica spends a couple of hours each day on the fi rst step of the process, writing a draft patent specifi cation. This involves talking to the inventor to fi nd out what is new about the invention. For a new drug, for example, Jessica would spend some time researching other potential uses for the compound, or alternative ways to produce it, to ensure that no-one could change any aspect of the patent and claim it as their invention. She has to understand unfamiliar areas thoroughly and

quickly, making her work challenging but varied.

In the next step Jessica searches through existing patents to fi nd out what applications her client’s rival companies have made. This makes sure her client’s invention isn’t already protected. Jessica then fi les the application with the relevant patent offi ce, which is usually the European Patent Offi ce (EPO), where the examiners decide whether or not to grant the patent. She will receive a report from the EPO examiner and after discussions about any amendments with the inventor, she writes a response to the EPO. Throughout this process Jessica is working to tight deadlines and must ensure these are adhered to otherwise this could result in delays to the invention becoming commercially available.

A Sometimes Jessica will work on ‘assignments’, where one company is taken over by another and attorneys have to decide who should own the patents that were held by the original company. Another aspect of the job, which Jessica particularly likes, is ‘opposing’ an existing patent. This means scrutinising a patent that is stopping her client’s invention from getting to market. ‘Finding a fault or loophole with the patent is extremely satisfying’, she says, ‘because this could be key to getting my client’s invention to market’.

Having science qualifi cations is important for Jessica because she has to be able to write and understand the technical language, and appreciate what her clients want from their invention. She has to learn the background to a new invention, often in just a few hours, but still have an eye for detail – a wrong number or date would be disastrous for her client, she said.

J It will take Jessica four to fi ve years before she is qualifi ed, during which time she will be working full-time in the fi rm as well as attending regular tutorials and chemistry practice group meetings to discuss the latest cases. ‘The most satisfying part of my job is being able to balance the needs of the inventor with the scientifi c discipline required by the EPO, and knowing that I have helped my clients get the best out of their invention’.

PATHWAY TO SUCCESS � 2009–pr ent, trainee patent a� orn� , Carpmaels & Ransford, London

� 2006–10, PhD at St John’s College, University � Oxford

� 2002–06, MChem in chemist ry (1st) at St John’s College, University � Oxford

� 2004–2006, chemist ry, biology, physics and maths A-levels, South Cheshire College


£50 OF TOKENS TO BE WON!£50 OF TOKENS TO BE WON!

March PRIZE WORDSEARCH No. 49 winnerThe winner was Harrison Shifrin from Hertfordshire. The nine-letter word was CYTOKINES.

8

ISSUE MAY

Download a pdf of this issue at: www.rsc.org/EiC

Students are invited to fi nd the 32 words/expressions associated with the analysis of belladonna hidden in this grid. Words read in any direction, but are always in a straight line. Some letters may be used more than once. When all the words are found, the unused letters, read in order, will spell a further four-letter word. Please send your answers to the Editor at the usual address to arrive no later than Monday 7 June. First correct answer out of the editor’s hat will receive a £20 HMV token.

PRIZE WORDSEARCH No. 50

ACID

ALKALINE

ANALGESIC

ATROPA BELLADONNA

BIOSYNTHESIS

BLOOD

BLOOD BRAIN BARRIER

BRAIN

CONDENSATION

DEADLY NIGHTSHADE

DEGRADATION

DISTILLATION

DOSE

DRUG

EUPHORIA

EXTRACTS

FRUIT

HYDROLYSIS

HYOSCINE

NARCOSIS

NERVOUS SYSTEM

NEUROTRANSMITTER

OPHTHALMOLOGIST

PLANT

POTENT

PSYCHOLOGICAL

RACEMIC

SPECTROSCOPIC

TOXIC

TROPANE ALKALOID

TROPINONE

VACUUM

A T R O P A B E L L A D O N N A B

N S M E T S Y S S U O V R E N L E

E I C O N D E N S A T I O N O A D

U G D S E S N H T I U R F O S C A

R O E I U T I Y O G U R D I P I H

O L G S P C L O X T B B T T E G S

T O R Y H A A S I N R L R A C O T

R M A L O R K C C A A O O L T L H

A L D O R T L I I L I O P L R O G

N A A R I X A N S P N D I I O H I

S H T D A E B E P O T E N T S C N

M T I Y N A R C O S I S O S C Y Y

I H O H R A C E M I C O N I O S L

T P N R V A C U U M A D E D P P D

T O I C I S E G L A N A A C I D A

E E B I O S Y N T H E S I S C L E

R T T R O P A N E A L K A L O I D

Students are invited to solve Benchtalk’s Find the element puzzle, contributed by Dr Simon Cotton. Your task is to complete the grid by identifying the eight elements using the clues below.

ACROSS1. This metal is not attacked by either conc. HCl or H2SO4 in the

cold, but reacts quickly with conc. HNO3. 2. A Group VI element that exists in allotropic forms.3. An element that forms long chains of its atoms in many

compounds.4. Metal displaced from solutions of its salts by zinc but not lead.5. Element produced when sodium reacts with water.6. Non-radioactive halogen with the highest boiling point.7. Metal forming a hydrogencarbonate that is stable as a solid.8. Metal found in hard water which can form limescale.

If you have found the correct eight elements, in 9 down you will have generated the name of an alkali metal.

Please send you answers to: the Editor, Education in Chemistry, the Royal Society of Chemistry, Burlington House, Piccadilly, London W1J 0BA, to arrive no later than Monday 7 June. First out of the editor’s hat to have correctly completed the grid will receive a £30 HMV token.

FIND THE ELEMENT No. 13

Find the element no. 12 solutions and winnerThe winner was Harriet Bertram from Kemnay Academy, Kemnay, Scotland.

1 9

2

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8 8

1 10

2

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c h l o r i n e

s o d i u m

a l u m i n i u m

i r o n

n e o n

z i n c

s u l f u r

b r o m i n e


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