Is IB chemistry too easy?
Posted on 04 May 2012 at 16:20h
Has IB Chemistry 'dumbed down' over the years? This is a difficult, if not impossible, question to answer as the skills and knowledge that a student taking the programme now are required to master are very different to those from the past. It is however a pertinent question to ask as a report has been published in the UK decrying the fact that the mathematical content of comparable science courses (i.e. British A levels) has diminished considerably and students are no longer being adequately prepared to study science degree courses at university or to enter industry. The report is published by SCORE (a partnership of the Association for Science Education, the Institute of Physics, the Royal Society, the Royal Society of Chemistry, and the Society of Biology). SCORE looked at both the mathematical requirements of A levels and also at the level of questions asked in examinations. The full report is available as a pdf file and a short article that summarises it can be found as a BBC News item. The conclusion of SCORE was that over the past few years the examinations have become much easier in terms of the amount and level of mathematics required to answer science questions. Although they did not include any of the IB science subjects in this survey I suspect they would have found the same trend.
Certainly in recent years the concepts that need to be understood by IB Chemistry students have still been quite challenging but they have not required a strong mathematical background or understanding. Modern analytical chemistry and the reaction mechanisms in Further Organic Chemistry are two good examples of this. Spectroscopy and organic reaction mechanisms were absent from the IB Chemistry programme prior to 1996 and many other concepts, particularly in the options, have also been introduced since then. However the amount of physical chemistry requiring mathematical ability has reduced considerably. Topics such as colligative properties, Kp, integration of rate equations, partition coefficients, partial pressures, radioactive decay, use of Planck's constant etc. have all been taken out and others such as solubility product are now just a small avoidable part of a particular option. In terms of mathematical requirements the use of logarithms and putting an equation into its logarithmic form have all but disappeared and there is no need for students to use calculus or solve quadratic equations.
Does this actually matter? Students seem to find it hard enough to perform simple arithmetical manipulations such as deal with proportionality and work out molar calculations. However, will they really be able to cope with studying a science or science-related subject at university if they cannot perform more complex mathematical manipulations? Today’s IB Chemistry students might be horrified to learn that in the early years of the IB the multiple choice paper contained sixty questions (to be answered in 90 minutes) each with five possible answers many of which contained quite complex calculations. Are we in danger of dumbing down our subject too much by ignoring the mathematics underpinning it? Many universities now have to run remedial maths classes for Chemistry students in order to try to bring them up to the required level. These are the sort of questions that the subject review body should be asking as they come to write the new programme for 2014 onwards - particularly as SCORE has called for a review of the mathematical requirements for Chemistry A level.
Nanosponges
Posted on 16 April 2012 at 21:45h
A sponge that can absorb 100 times its own weight in oil. This novel way to clean up oil spillage using carbon nanotubes has recently been reported in Scientific Reports by a team working at Rice University. Nanotechnology is one of the topics on the IB Option C; Chemistry in industry and technology and this latest discovery neatly overlaps with the environmental issues of cleaning water contaminated by oil spillage. What the team at Rice has managed to do is ‘weld’ carbon nanotubes together using boron to form covalent linkages. The resulting three-dimensional blocks, which contain billions of nanotubes, can act like sponges as they contain more than 99% air. They are also able to conduct electricity and be manipulated by magnets. The blocks repel water but are extremely oleophilic – i.e. they love water. Because of their low density they can float on water and absorb spilled oil. What is even more remarkable is that the process is reversible. The oil can either be stored for later use or burned off leaving the ‘sponge’ able to soak up more oil. A video has been produced on You Tube which shows this process. If these blocks can be made on an industrial scale then they have enormous potential to clean up oil spillage wherever it may occur.
Origin of the moon
Posted on 01 April 2012 at 14:23h
As well as being a fascinating subject in its own right Chemistry can be used as a tool to solve many problems. One interesting example that has emerged recently is “What is the origin of the moon?”
The most usual explanation is that during the formative period of the Earth some 4.5 billion years ago a giant asteroid collided with the Earth. The moon, which has a diameter roughly one quarter of that of the Earth and contains1/ 81 of its mass, is thought to have been flung off from the Earth as a result of this collision. This is known as the Giant Impact Hypothesis. However, there is no real hard evidence to support this and several reasons to question its validity. For example, the energy produced in such a collision should have been enough to produce a huge global ocean of molten magma and yet there is no evidence of the heavier material sinking into the Earth’s mantle. Similar collisions during the formation of Venus are also thought to have occurred during its formation and yet Venus does not have a moon.
So how can Chemistry help to solve the problem? In an earlier blog I talked about how the accurate measurement of isotopic mass has led to relative atomic masses being quoted as between two values rather than being given precise values. This is because the relative atomic mass of an element can vary slightly depending on the original source of the element. Titanium is an element with a very high boiling point and so would be less likely to be vaporised during the huge release of energy following a cataclysmic collision. Asteroids that have fallen to Earth have been shown to have a different ratio of 50Ti to 47Ti so it would seem reasonable to assume that if the moon was formed from such a collision the ratio would be different on the moon to that on Earth, A team from the University of Chicago using samples of rock brought back from the Apollo missions has shown that the ratio of 50Ti to 47Ti is in fact exactly the same on both the Earth and the moon. This of course is achieved using high resolution mass spectrometry and could be used as a nice example to support the teaching of the IB Assessment Statements 2.2.2 and 2.2.3 The findings suggest that the moon only had one ‘parent’, the Earth, and not two as previously proposed and hence falsifies the Giant Impact Hypothesis.
As well as the concept of falsification you can of course bring in a bit more Theory of Knowledge and find some possible flaws in the argument. It may be that the huge asteroid hitting the Earth did not contain any titanium so of course the ratios would then be the same. Coincidence may play a part and the asteroid may by chance have had exactly the same ratio of the two isotopes as the Earth. It is also possible that the temperatures reached were so high that the titanium (probably in the form of its oxides) did in fact vaporise during the impact and hence distribute itself equally between the two bodies. There are serious counter arguments to all of these possible hypotheses. So at the moment the evidence is now in favour that the entire moon came from the Earth alone. More than 40 years after the Apollo missions there is still no good theory as to exactly how that might have happened.
The EE viva voce
Posted on 07 March 2012 at 13:28h
It’s Extended Essay marking time again. Although the essays do not actually have to be with the examiner until 15 March many have already arrived. One aspect that is very noticeable is the quality of the comments written by the supervisor on the inside of the cover sheet. The worst are where there is no comment and I feel sorry for the student who has been supervised by someone who cannot even be bothered to comment on their work. Many of the best supervisor’s comments refer to the viva voce and give some of the questions asked and the student’s responses. It is not a requirement that a viva voce is given but I feel it makes for a good closure to the whole Extended Essay process. Unless the supervisor is concerned that the work has been plagiarised or that the student does not understand what they have written it should not be a formal oral examination – more an opportunity for the student to reflect on what they have learned. Perhaps the name viva voce is unfortunate as normally it is applied to the oral defence of a thesis such as a Ph.D (unless it refers to the American Indie Rock band from Portland – see image). I was rather concerned to find one school treating it exactly like a Ph.D oral. Before the supervisor’s written report there was a statement to the effect that the viva voce takes the form of a ten minute public defence of the Extended Essay in front of ‘a team of EE Examiners’, invited guests, other Diploma students etc. The student has to outline the steps taken to decide the research question, how the sources of information were identified, how the data used in the EE was obtained, the results of the research, the conclusion drawn and the bibliography of sources used. At the end of the process the ‘team of EE examiners’ has to be satisfied that it is the candidates own work. I pity the students in this school. They already have enough pressure on them to complete the IB Diploma – extra pressure like this is totally unnecessary and goes against the spirit of what is intended by an EE viva voce – that is, a one to one discussion with the supervisor.
More on the new curriculum
Posted on 29 February 2012 at 00:41h
I last blogged about the proposed curriculum changes in December. Since then more progress has been reported on the Online Curriculum Centre by the review teams. These reports are available to IB teachers who are registered to use the OCC. The chemistry review gives details of the new Curriculum Model, an overview of the new Syllabus and the Assessment Model.
Essentially the time spent on the Core is increased from 80 hours to 95 hours and the AHL is increased from 55 hours to 60 hours. The option time is reduced from 30 hours to 15 for Standard level and from 45 hours to 25 hours for Higher Level. The Group 4 project (10 hours) remains and the total time for investigations remains unchanged at 40 hours for Standard Level and 60 hours for Higher Level. There is a statement that the amount of material in the Core/AHL will be reduced. The titles of the 11 Core topics and the 9 AHL topics remain unchanged but there will be some rearrangement of sub-topics. The four options have been identified as Materials, Biochemistry, Energy and Medicinal Chemistry. Students will only need to choose one of these options.
Standard Level will only be examined by three components one of which is the IA. This means the number of exam papers has been reduced from three to two. Paper 1 (¾ h) will be 30 multiple choice questions on the Core and counts for 30% of the total marks. Paper 2 (2¼ h) will be short and long structured questions based on the Core and questions on the option. It will count for 50% of the marks – the remaining 20% is made up by the IA. Higher Level will still have 3 exam papers. Paper 1 (1 h) will contain 40 multiple choice questions as now and will count for 20% of the total mark. Paper 2 (2¼ h) will consist of short and long structured questions and some extended questions all on the Core/AHL and will count 40% towards the final mark. Paper 3 (1¼ h) will consist of questions on the option and a data based question which may test skills and understanding learned through the IA and will be worth 20% of the total mark. The remaining 20% of the total mark is made up by the IA.
We discussed these proposals during a workshop for experienced IBDP Chemistry teachers that I ran in Berlin last weekend. Before the workshop I had got some clarification to some of the less clear points from Fiona Clark, the Chemistry Curriculum Subject Area Manager (SAM) and I am very grateful to her for all her help.The teachers were generally of the view that they would need to see the exact content of each topic and sub-topic on the Core and AHL before making specific comments. However the following points were made:
1. They were surprised at the very low response to the questionnaires sent to teachers and felt that to base a new programme on returns from only 23 teachers is worrying. It may be that the IB expects all teachers to respond to questionnaires when they are put on the OCC but the reality is that very few teachers actually look at the OCC.
2. The options seem biased towards biological chemistry. They were concerned that the two options Analytical Chemistry and Further Organic Chemistry have been dropped as these are highly regarded by universities. They accept that some of the content of these current options will be in the core/AHL on the new programme but are at a loss to see how much since the overall content of the current core/AHL is being reduced. Much of the proposed Materials option may be difficult to test at an Objective 3 level.
3. There was a genuine disagreement about reducing the Core/AHL content. Some were in favour but others felt that the current content is about right and are concerned about ‘dumbing down’ the programme.
4. Some felt that if the Core/AHL content is being reduced then errors and uncertainties (Topic 11) could be removed as it is less important than real chemistry. One person suggested that some of the more difficult concepts such as hybridization could be removed but others disagreed.
5. The participants were mystified as to the emphasis being put on the Nature of Science. How is this different to the current emphasis on TOK and ‘Aim 8’ and will it actually be assessed?
6. Concern was expressed that the Standard Level exam would not necessarily contain a data-response question nor would the IA be necessarily assessed in the written papers whereas both of these are specified as being included at Higher Level.
7. Normally the weighting of an exam paper is related to the time spent. It seems odd that the ¾ h Paper 1 (30 multiple choice questions) for Standard Level counts for 30% of the total marks whereas Paper 2 which is three times as long (2¼ h) only counts for 50% of the marks. Contrast this with Higher Level where the 1h Paper 1 (40 multiple choice questions) is only worth 20% of the final marks.
The workshop then looked at the proposed changes to the IA. Essentially the Internal Assessment will consist of one written ten hour open investigation/scientific exploration which will count for 20% of the total marks. The Group 4 project will count for another ten hours and be assessed for personal skills. Teachers will be free to devise their own practical programme for the remaining 20 hours (SL) or 40 hours (HL).The investigation will be assessed for Context, Analysis, Communication and Reflection - each on a 0-4 point scale. Manipulative skills will be assessed summatively as at present. The investigation will allow a wider range of activities than the present traditional hands on practical investigation. For example, using a spreadsheet for analysis and modelling, extracting data from a database and analysing graphically etc, simulations – must be interactive and open ended and more qualitative work will be allowed. ” Hands on investigations would remain as a possible IA task but the detailed assessment of specific aspects of it would be undertaken in the written papers.
The participants at the workshop appreciated that one of the major strengths of the IB is that teachers are free to devise much of their own practical programme. They also felt that it would be a good opportunity for the IB to introduce the idea of including specific manipulative skills (e.g. distillation, reflux, recrystallisation, chromatography etc.) in the unassessed work, much in the same way that ICT is now. However they also expressed concerns about many of the proposed changes to the IA. Specifically:
1. Since only one piece of written work will be submitted participants felt this could disadvantage ESL students. They also felt there was much scope for potential academic dishonesty. They see it as high risk – an ‘all or nothing’ scenario whereas the current system allows for development through learning.
2. The fact that simulations seem to be preferred to actual ‘hands on’ experimentation was seen as worrying.
3. They foresee a huge problem with student overload. Currently the IA is spaced out over the two years. The new proposal will add to the demands on students in their final few months of the two year course. There was also a workshop for experienced IB coordinators running at the same time and they too were extremely concerned about this.
4. Who will be responsible for determining the specific ‘research questions’ for the investigation? Teachers already find it hard to help students come up with EE research questions. Indeed, as proposed, the investigation sounds like a mini EE in Chemistry.
5. In the report the IB has finally admitted that the current IA is not working (“Group 4 IA has been problematic for many years. The Internal review committee came to the conclusion that the current IA cannot be fixed…”). The participants felt that assessing the proposed new IA will cause just as many, if not more, marking and moderation problems.
6. The assessment model mentions setting questions on specific aspects of ‘hands on’ practical work on Higher Level Paper 3 but no mention is made of how these specific aspects will be assessed for Standard Level.
7. Concern was expressed about how different schools will implement this new system. How will the ten hours be allocated? It cannot be outside the normal schedule as it will cause more disruption to other subjects on top of the Group 4 project. It may be difficult for weak students to come up with their own ideas and there is the question of the availability or lack of resources in poorly resourced schools.
It was agreed to pass on all these comments and concerns to the IB.
A young chemist
Posted on 12 February 2012 at 18:11h
I suppose in our heart of hearts IB Chemistry teachers know that they are unlikely to change the course of science by coming up with a revolutionary paradigm shift. It is not that we are lacking in intelligence and imagination – it is simply that most of us are just too old. By the time he was 23 Newton had discovered calculus, the law of gravitation and published Optics. Einstein was 26 when he published his three papers on special relativity, the photoelectric effect and the equivalence of matter and energy in 1905. Darwin was aged 22-27 when he came up with the theory of evolution on HMS Beagle. Perhaps we will just have to leave it to our young 17-19 year old IB Diploma students but unfortunately even they may now be too old by today’s standards.
Ten year old Clara Lazen of Border Star Montessori School, Kansas City had been given a ball and stick molecular modelling kit by her school science teacher, Ken Boehr. The rules were that the black balls (carbon) must have four ‘sticks’ attached, the red balls (oxygen) two sticks and the blue balls (nitrogen) three sticks. She produced a model and asked her teacher whether it represented something that actually existed. Ken could not recognise it so sent a photograph of it to a friend, Dr Robert Zoellner (left) who is a lecturer in Chemistry at Humboldt State University in California. Zoellner confirmed that the compound she had modelled did not exist in nature and had not so far been synthesised synthetically but that it should be possible to make. He called the molecule tetranitratoxycarbon, C(CO3N)4 and predicts that it will have explosive properties. Zoellner has published an article on the possible isomers of tetranitratoxycarbon together with Boehr and Lazen as co-authors in Computational and Theoretical Chemistry.
methane.jpg "Tetrakis(nitratoxycarbon) - Clara's modelled molecule")
There are some interesting Theory of Knowledge applications to this story. It is a good illustration of serendipity. Clara discovered the molecule ‘by accident’. How many teachers might have said that as they did not recognise it then it probably could not exist and so would have dismissed it? By not dismissing it Ken acted in a similar way to Fleming who came back to his lab to find mould growing on his unwashed petri dishes – rather than throwing them away Fleming followed up his observation and discovered penicillin – Ken Boehr followed up Clara’s model and Robert Zoellner confirmed that isomers of tetranitratoxycarbon should exist.
Of course they do still have to be made!
A video of Clara's discovery 
from Fox News posted on YouTube.
Promoting the IB
Posted on 01 February 2012 at 20:13h
As well as teach their subject I guess most, if not all, IBDP chemistry teachers at some time also have to play the role of an IB ambassador. For many this may be counselling pre-IB students and their parents as to which course to take. This can be particularly relevant in schools where students can opt to take either the IB Diploma or stay with their own national curriculum. It can often be a difficult decision for students and parents to make. They need to be given the correct information to make an informed choice. The demands of the IB are often higher than those imposed by national curricula and students need the benefits of an IB education explained clearly to them. It can be helpful to have some backup to support your arguments.
In December I blogged on a report by the British Council and Think Global which had researched what 500 top executives were looking for when recruiting employees. Recently two more articles have been published which provide more good ammunition. One is an interview in Education News in the USA with Jeffrey Beard, the Director General of the IB. I guess this could be criticised because it is effectively the IB blowing its own trumpet. The article does shoot itself in the foot a bit with statements like “students need to do a 4500 (sic) word research paper” and it contains an image (see right) showing five students watching a sixth student use a pipette with none of them wearing safety glasses. Nevertheless some good points are made comparing the IB with AP. It highlights the fact that students are assessed using the same criteria worldwide and also stresses the importance of good teaching and the professional development programme for IB teachers as well as the usual strengths of international mindedness and the TOK and CAS programmes.
Perhaps the best endorsement for the IB comes from people (like the 500 top executives) with no obvious affiliation to the IB. There is a really good recent article in the Telegraph on comments made by Dr Alice Roberts. Dr Roberts is well known to television audiences in the UK from her roles in the BBC’s 'The Incredible Journey' and 'Coast'. Previously she worked as a junior doctor in the UK before spending the past ten years lecturing on anatomy at the University of Bristol. She has now been appointed to the new post of Professor of Public Engagement in Science at Birmingham University. She praises the education that the IB offers compared to British A levels saying, “Of the students I saw applying to medical school, the ones that had done the IB seemed to be more rounded individuals. “I don’t think we should be asking people at 16 if they are an artist or a scientist and making them choose between the two”.
Armed with articles like these and with the personal experience you have gained with your own IB students you are in a good position to speak with authority on the merits of an IB education.
Poisonous clothes
Posted on 19 January 2012 at 17:28h
One of the purposes of educating our students is to help them to make sense of newspaper articles about ‘Chemistry’. Almost every day there is some scare that involves the use of ‘nasty chemicals’ – how seriously should we take these? There is no right answer to this question as each case must be judged on its own merits but hopefully we can provide our students with the tools to make their own sensible conclusions.
In today’s Daily Mail there is an article about how your clothes can poison you. This is not really new as a similar report appeared in the New York Times in December 2010. Basically the articles claim that manufacturers put formaldehyde into clothes to make them smell fresh and keep them wrinkle free. They then go on to state that “formaldehyde, a highly toxic, colourless gas, has been linked to skin irritation and allergic reactions. Even more worryingly, the chemical is classified as a human carcinogen by the International Agency for Research on Cancer.”
So how valid are these claims? Formaldehyde is of course the old name for what we now call methanal. Our students are likely to come across methanal both in biology (formalin, used to preserve specimens, is methanal in water) and in Topics 10, 20 and Option G: Further organic chemistry. They may, or may not, actually handle it practically. Since it is a gas most teachers use propanal or butanal rather than methanal as an example of an aldehyde in practical work. Even so, students will be breathing in methanal in their daily lives as it is found both naturally and as an ingredient in certain wood products such as plywood and fibreboard, in foam insulation and paints, varnishes and glues. It is also present in automobile exhaust.
Methanal is certainly toxic to humans if ingested and breathing in concentrations above 0.1 ppm in air has been shown to irritate the eyes. In those people who suffer from certain allergies it may cause headaches and breathing difficulties even at this low level. The evidence that it is carcinogenic is less certain but is sufficient for methanal’s status to have been upgraded from ‘reasonably anticipated to be a human carcinogen’ to ‘known to be a human carcinogen’ by the US National Toxicology Programme’ as recently as June 2011.
It seems on balance that the newspaper articles are right to be concerned. Why expose yourself to unnecessary amounts of methanal? It makes sense to wash and air new clothes thoroughly before wearing them or hanging them in your wardrobe. Alternatively, in these times of economic hardship, perhaps it is even worth considering wearing ‘hand me downs’ or frequenting charity shops.
2011 roundup
Posted on 22 December 2011 at 20:40h
Too busy teaching to read all the journals (and my blog!)? You can take the lazy way out and catch up on all the latest developments in Chemistry during the past year by reading the article “Cutting edge Chemistry in 2011” published in the December edition of Chemistry World.
Perhaps the most unusual and disputed discovery was reported by Felisa Wolfe-Simon et al. working at the Nasa Astrobiology Institute in the US. They claim that certain bacteria from Mono Lake in California use arsenic rather than phosphorus in their DNA backbone. Presumably since phosphorus and arsenic are in the same group it simply replaces phosphorus to form an arsenate rather than a phosphate so the diagram on the right (taken from Neuro Dojo) is overdoing it somewhat. If this turns out to be true – and many chemists doubt it – then it is almost as surprising as the most contentious physics claim this year that neutrinos can travel faster than the speed of light. But there again Santa must be able to travel faster than the speed of light to get down all those chimneys in one night. Have a good Christmas.
Global skills
Posted on 15 December 2011 at 15:19h
An interesting report has just been published jointly by The British Council and Think Global. It is entitled “The Global Skills Gap: Preparing young people for the new global economy”. The report is based on the findings of interviewing 500 chief executives and board level directors in companies with at least 10 employees. These chief executives were all based in the UK so although strictly speaking it refers just to Britain I’m suspect that the findings are also applicable worldwide. They very much support my stance on education. As those of you who have perused my website will have gathered I am very concerned about the way in which 16-19 teaching has become more and more like drilling with the whole emphasis solely on attaining good examination results. This has been at the expense of focusing on providing a good all-round education with the emphasis on understanding and critical thinking so that students are able to put their knowledge into a wider perspective.
The precise statistics are given in the report but essentially what the survey found is that when they are looking to recruit new employees more employers say that knowledge and awareness of the wider world is more important than class of degree or choice of subjects studied at school.
Following this up three quarters of UK businesses think that the UK is in danger of being left behind emerging countries unless students are taught to think more globally and lead more sustainable lives.
Some examples of schools that are helping young people to think more globally are given. As with many documents originating from the UK it is very much A level orientated but what they are looking for is exactly what the IB specifically aims to be doing already: "The aim of all IB programmes is to develop internationally minded people who, recognizing their common humanity and shared guardianship of the planet, help to create a better and more peaceful world."1
What this report shows is that we would be much better serving our students by focusing on the Learner Profile and the International Dimension, ‘Aim 8’ and TOK, CAS etc. than by narrowly focusing only on examination results. The very qualities that are not really examined at the end of the course are those qualities that employers most value when they are recruiting prospective employees. What is more important – getting our students into university or providing them with the skills that they will need to be employable in the future?
Hopefully through a good IB education we can do both.
1 Introduction to the IB learner Profile
Curriculum review progress
Posted on 02 December 2011 at 11:55h
The review of the current Group 4 curriculum is currently underway to produce a new curriculum for teaching starting in September 2014 with the first examinations in May 2016. One report on the first meeting has already been published (see my earlier blog) but in true political style leaks are beginning to appear on the further progress that has been made even though no further official reports have been produced yet.
At The Hague IBAEM conference in late October David Jones, the Curriculum Area Manager for Group 4, gave a presentation on the proposed changes. This is available on line as a pdf file. Shortly afterwards Fiona Clark, the Curriculum Subject Area Manager for Chemistry, gave a similar presentation in Mumbai, India. It is not clear exactly what is definite and what is still in the proposal stage but the following significant changes appear to be likely for all the main Group 4 subjects: Physics, Chemistry and Biology.
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The number of options will be reduced from 2 out of 8 to 1 out of 4 for both SL and HL
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The number of written papers at SL will be reduced from 3 to 2
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There will be a new internal assessment at SL and HL
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The nature of science is to be the overarching theme in Physics, Chemistry and Biology
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The Group 4 project will continue with an emphasis on collaboration between schools
- Physics, Chemistry and Biology will continue at both HL and SL but there will be a new science course at SL only. (The philosophy of this new course is “to bring forth through student centred activities, the wonder of science, its power to change the world for good or bad and its concomitant limitations.” It will explore six big ideas in Science which illustrate the nature and methodologies of the subject. These ideas are: The Universe, Atomic Theory, Medicine & Health, Evolution, Radiation, and Earth Science.)
Changes to the IA.
What will affect teaching most are the proposed changes to the Internal Assessment. The Chemists met again in November and the detailed proposals for Chemistry are still to be released but it does seem as though the IA changes will be subsumed into the new Chemistry HL and SL programmes. According to David Jones, “The model proposed is for one, open-ended practical investigation with new generic criteria that will allow both a wider range of activities satisfying the varying needs of the three subjects and more agreement on the marks awarded as a result of the application of the criteria. It would comprise 20% of the overall assessment. The criteria would need to reflect the learner profile and the overarching Nature of Science theme for the new group 4 courses.”
It appears that the practical activities programme will remain at 40/60 hours and the group 4 project will also remain and be assessed, as now, with the criterion personal skills.
The Assessed task will be one investigation/scientific exploration. It will be presented as written task. It is expected that the task will allow a wider range of activities than the present traditional hands on practical investigation. As well as more qualitative work being allowed these tasks might include
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Using a spreadsheet for analysis and modelling
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Extracting data from a database and analyzing graphically etc
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Simulations –which must be interactive and open ended
The present traditional hands-on investigation would remain as a possible IA task (but the detailed assessment of specific aspects of it would be undertaken in the written papers). The tasks produced would be complex and commensurate with the level of the course. They would require a purposeful research question and the scientific rationale for it and a cognitive component - critical scientific thinking element (thinking like a scientist).
The one assessed investigation/scientific exploration will have the same assessment criteria for SL and HL but may have different grade boundaries or weighting. The draft criteria for this assessment are Context, Analysis, Communication, and Reflection, each on a possible 0-4 point scale.
The rigour of the IA will be maintained by ensuring the criteria reflect the demanding conceptual understanding required by making the nature of science (NOS) the overarching theme. The moderation will probably be based on e-portfolios and e-moderated by seeding.
My comments
This is clearly a major change from current practice and has the potential to be exciting and innovative. It also has the very real potential to cause similar unhappiness with the moderation process that currently exists so the assessment model will need to be carefully planned beforehand. There is also serious potential for academic dishonesty as this one investigation will be worth 20% of the total final marks. The four criteria as proposed do not seem to be awarding creativity which is a missed opportunity. Hopefully, as the concept is developed, it will address the different ways in which Chemists, Physicists and Biologists practice their science so that different types of investigations are possible in the different disciplines. My initial thought is that it is verging much more on an Extended Essay in the subject compared to the current method of internal assessment. Will this encourage or act as a disincentive to students choosing an Extended Essay in Chemistry? Indeed, will there still be a need for Extended Essays in science?
Paraquat
Posted on 28 November 2011 at 15:51h
I took some time off recently and went on a trip to India. Whilst wandering around the fields adjacent to the backwaters around Alappuzha (formerly Alleppey) in Kerala I came across a farmer spraying his rice crop (above). I noticed that he was not wearing any protection against the spray and wondered what chemical(s) he was actually spraying on his crops.
At the edge of the field I came across his discarded canisters (left and expanded on right). He was using the herbicide paraquat. Paraquat is a substituted bipyridine salt and has the chemical name N,N′-dimethyl-4,4′-bipyridinium dichloride. Although herbicides and pesticides were once on the old Applied Chemistry syllabus they no longer form part of the food option so IB students would not be expected to know anything about them. However paraquat could be used illustrate a couple of useful concepts that are on the current syllabus. (Remember that future exam questions may well use unfamiliar substances such as paraquat to test the understanding of objective 3 concepts that are on the syllabus.)
One is the international aspect. Although paraquat is one of the most widely used herbicides in the world farmers and gardeners who live in the European Union cannot purchase it or use it as it has been banned since 2007. This is because it is very toxic and there is no known antidote – hence my surprise at seeing the farmer use it with no protection (and leaving the canisters lying around where possibly children could find them and play with them). The laws governing the use of certain chemicals in different countries provide a good example of the international aspects of chemistry.
The second is that paraquat provides a good example to test the understanding of hybridization for Higher Level students in Topic 14.2. Students have learned that the nitrogen atom is sp3 hybridized in both ammonia and the ammonium ion. Ask them what the hybridization of the nitrogen is in paraquat. They should be able to deduce that as both nitrogen atoms (actually ions) are part of the aromatic ring system the hybridization is the same and the nitrogen must be sp2 hybridized. Two of the p orbitals hybridize with the s orbital to give three sp2 hybrid orbitals with bond angles of 120o leaving one electron in the p orbital of each nitrogen ion to contribute to the delocalisation within the aromatic ring.
Peer reviewed articles
Posted on 02 November 2011 at 12:01h
Two common errors when students write extended essays in Chemistry are that they only use the Internet as a reference source and that they fail to address Criterion F properly. Criterion F deals with the application of analytical and evaluative skills appropriate to the subject. Chemistry students often look at this in a very narrow way and only concentrate on their own experimental procedure(s) as they have been trained to do for the Internal Assessment. Clearly students writing their EEs in other subjects such as History or English B have no experimental procedures so how do they address this criterion? The answer is that they look at the quality and reliability of their source material and chemists should also do this for all the secondary sources they have used. Searching the Internet may produce an excellent and reliable source but it may also produce some that are highly unreliable and possibly even completely wrong. I have often see students use unbalanced equations, wrong structures and wrong chemical statements that they have quoted from an Internet source without ever challenging the reliability of the source (see examples on the webpage on Criterion F on EE assessment). The reason why students need to go back to the original article or a reputable text book if at all possible is that it has been peer-reviewed. No such guarantee exists for an Internet site.
It is interesting to look at the history of peer-reviewing. The Royal Society claims that the first scientific papers to be peer-reviewed were published in the first edition of the Philosophical Transactions of the Royal Society in 1665 (left). The Royal Society has just announced that it is making available to the public free of charge all the archives of the society which include the publications in the Philosophical Transactions. Over sixty thousand articles are accessible from their online archive search. These include such gems as Isaac Newton’s first published scientific paper in 1671 and early papers by Michael Faraday such as ‘The source of power in a voltaic cell’ written in 1840. It is well worth getting your students to look at some of these early articles and see the value of published scientific research. For example in 1870 Thomas Huxley FRS wrote: “If all the books in the world, except the Philosophical Transactions, were to be destroyed, it is safe to say that the foundations of physical science would remain unshaken, and that the vast intellectual progress of the last two centuries would be largely, though incompletely, recorded.”
What could be an interesting exercise would be to mark one of these early papers according to the IB Extended Essay criteria. What conclusion could you draw if they did not score too highly? Perhaps the skill and demands of writing scientific papers has developed and changed considerably during the past hundred years or more, or could it be that the EE criteria are not really appropriate for judging cutting edge science? What do you think?
Failing Extended Essays
Posted on 18 October 2011 at 21:05h
Essentially a student needs 24 points to obtain an IB Diploma but there are also other conditions. For example, they must obtain at least twelve points in their Higher Level subjects and must not score less than a Grade 3 in any HL subject. So a 5, a 4 and a 3 would be acceptable but two 6s and a 2 would be a failing condition. Since 2010, students who score 28 points or less will also fail to be awarded a Diploma if they score an E grade in their Extended Essay.
Extended Essays are marked out of 36 points and an essay that scores less than 8 out of 36 is deemed ‘poor’ and is awarded an E. When this rule first came in last year I had to remark all the Chemistry Extended Essays before the grades were announced to confirm that the E mark was correct. In fact only very few were awarded an E. In all the Group 4 Extended Essays in May 2010 only 188 out of 7083 candidates obtained an E grade, that is, 2.7%. The 2011 Statistical Bulletin has not been published yet but the figures for November 2010 are very similar. 21 out of the 776 Group 4 candidates were awarded an E Grade. This is also 2.7% of the candidates. I suspect some of these would have scored less than 24 points and so failed the Diploma anyway but it seems a pity if a poor score on an EE means losing the Diploma.
An Extended Essay is a piece of research work but it is also an exercise in getting students to report their finding in an acceptable academic manner and the marking criteria reflect this. It should actually be possible for all students to gain at least satisfactory (a score of 16 or more out of 36) simply by addressing the criteria irrespective of the quality of their research. So why do some student score such abysmally low marks? From the Extended Essays that I see (and I see a lot of them) there would appear to be two main reasons. Upon analysis these actually come down to just one reason. It could be that the student is simply not up to it and is very weak but this is rarely the case. The first two marks are for Criterion A – Research Question. If this is not a sensible and reasonable topic to investigate in the subject within 40 hours then the Essay stands little chance. An unsuitable Research Question is one of the two main reasons. The other is that the Essay does not address the EE Assessment Criteria. In fact both of these come down to poor supervision since part of the supervisor’s job is to advise on the Research Question. I have much advice on this website on how to supervise an EE and have given examples of the common reasons why students do not score the maximum marks for each criterion. The point of this blog is to get you to assess your skills and knowledge as an EE supervisor. If you have not been trained demand that your school provides you with training before accepting a supervisory role – it is part of the responsibility of the school to provide training for all EE supervisors. It is not fair on students to provide them with a supervisor who cannot advise properly. No supervisor in Chemistry should allow some of the poor Research Questions I have seen. One of the most recent was “What is soap and what are the physical and chemical properties of it?” The resulting essay was just a narrative of properties found in any simple chemistry text book. There was no argument, no justification, no proper referencing of sources in the EE, and no analysis. With sound supervision even this mundane title could have been made to gain the student a minimum of 8 marks on some of the criteria but with no checklist and no proper supervision the student had no chance.
Be fair to your students – know how to advise them so that they can achieve at least a satisfactory C grade (let alone the minimum marks to avoid an E grade) just by following some very simple guidelines. It is not rocket science. No student should fail to get their IB due to lack of proper supervision on their EE.
E = m(c + a little bit)2
Posted on 24 September 2011 at 14:02h
IB chemistry teachers who fret over how to teach students the correct use of uncertainties in their IA practical write-ups can have a field day over recent work from CERN in Switzerland. Scientists have released their experimental results for all other scientists to evaluate as it would appear that they have measured neutrinos travelling faster than the speed of light.
Comparable velocities:
Beam of muon neutrinos: 299,798,454 ms-1
Speed of light in a vacuum: 299,792,458 ms-1
Speed of sound at sea-level: 344 ms-1
Usain Bolt: 10.4 ms-1
(measured as an average over 100 m)
Neutrinos are extremely small sub-atomic particles. There are three known different types of neutrinos and they all are electrically neutral. There is some debate about whether they have mass. If they do possess mass then it is extremely small – one estimate puts it as one ten thousandth of the mass of an electron. Because of these properties they can pass almost completely unhindered through matter. Scientists at CERN have sent a beam of muon neutrinos from the super proton synchrotron accelerator at CERN in Switzerland through the Earth’s crust to the Gran Sasso Laboratory – a distance of 730 km. The neutrinos are detected by special ‘bricks’ containing photographic emulsion film with a combined mass of over 1,000 tonnes. From the simple equation of distance divided by time their velocity can be calculated. The experimental result is based on the analysis of 15,000 neutrinos detections. It appears that the neutrinos travelled faster than the speed of light but the increase is less than 0.01 percent. This raises the fascinating question as to whether their ‘strange’ result is due to the uncertainties associated with their experimental technique or whether Einstein has been ‘proved’ to be wrong and something can travel faster than the speed of light. The research is by reputable scientists who have looked at every possibility and claim that their result is well above the margin of experimental uncertainty. Because of the enormous significance if their findings turn out to be correct they have released their work for others to examine and find potential flaws. What is needed now is for independent researchers to confirm or refute their results in separate experiments – these can be currently be performed in two other neutrino beam laboratories – one in the USA and one in Japan.
One question that I would like to ask is “Could an experiment be devised so that the velocity of neutrinos and the velocity of light could be measured simultaneously under the same conditions?” If this is possible, then a direct comparison could be made. At the moment the neutrinos are passing through the solid Earth’s crust through which light cannot travel.
If the results are confirmed as correct then much of physics and chemistry (relativity and quantum mechanics in particular) will need to be rewritten as the equation E = mc2 will no longer be absolute.
Chemistry/Art/IT project
Posted on 14 September 2011 at 13:52h
Those of you who have been to my workshops will know that I have a real interest in combining Chemistry and Art. In the past Science and Art were very much inter-related (see, for example, the painting “Experiment on a bird in an air pump” by Joseph Wright of Derby in 1768) but for the last two hundred years or so they have been portrayed as very different disciplines. Once they are exposed to the possibilities of combining Chemistry and Art most students find that it is something that they very much enjoy – particularly those who also study Visual Arts as one of their IB subjects. We also all know that students tend to be much more savvy with IT than most of us ‘oldies’ so why not give them a Chemistry/Art project to get involved in where they can really use their IT skills as well. Such a cross-curricula project can lead to a much greater appreciation and understanding in all three areas. Traditional teachers may say “but this is not on the syllabus” but, as the IB Learner Profile suggests, take a risk with a short amount of your allotted 240 or 150 hours. You might be surprised at the benefit that students gain, not only in increased understanding but also in their enjoyment and enthusiasm for Chemistry which will set them up for the more traditional parts of the course.
One person who has been doing this successfully is Kim Pimmel. In the example below called ‘Compressed 02’ he combines soap bubbles with a ferrofluid liquid and a red dye and sets it to music to create a story using macro lenses and time-lapse sequences. This involves both magnetic forces with the iron particles and also involves the hydrogen bonding attraction between water molecules which accounts for the capillary action. Kim also has several other examples of similar ideas shown as videos (the site calls them vimeos) on his site.
Chemistry, economics and mnemonics
Posted on 13 September 2011 at 00:15h
One element that everyone seems to know the value of is gold. Due to the ‘credit crunch’ and the continuing world economic uncertainties the price of gold has increased to nearly US$2000 per ounce. This represents an increase of about 30% over the past few months. Not a bad return for those canny investors who timed it right and moved out of equities (which have recently fallen heavily) and into gold.
However armed with a knowledge of both chemistry and economics and with a modicum of luck and good timing you could have done much better than this by investing in other precious metals. An investor who bought europium or dysprosium (right) in June this year would have tripled the value of their investment (an increase of 200%) in just three weeks! These two metals belong to a group of metallic elements which does not feature at all on the IB programme - the lanthanides. It seems odd that the lanthanide elements do not even get a mention, especially as some of them have very particular and important uses. Some of these uses are well-established but many are relatively very recent in origin. For example, cerium oxide has been used for a long time to polish glass but a more modern use is in catalytic convertors. Dysprosium compounds are highly susceptible to magnetization so one of their most recent uses is in computer hard drives and europium oxide is used in television and computer monitors due to its phosphorescent properties. Although some of the lanthanides (sometimes known as rare earth elements) are not actually that rare they are not found concentrated in nature so are expensive to extract and process. Because of their increasing uses in modern technology demand for them has increased. The two countries with the greatest production of lanthanides are the US and China. The rapid increase in price during June was because the Chinese severely cut back on production thus reducing the supply.
I do briefly mention the lanthanides to my students as they are the first f block elements. You could use the lanthanides to check whether Higher Level students really understand the relationship between position in the periodic table and electron configuration. Ask them for the electron configuration of element 61 promethium for example. For the IB under Assessment statement 12.1.6 they are required to be able to work out electron configurations for elements up to xenon (Z = 54). By extrapolation promethium, which only has seven more electrons than xenon, is likely to be either [Xe]6s25d14f4 (as it is underneath scandium and ytterbium) or [Xe]6s24f5 (as 4f comes after 6s and before 5d) which helps them to understand why the IB stops at xenon.
For those teachers and students who like mnemonics such as OILRIG or Richard of York gave battle in vain” you could even give them “Lazy chemists probably never prosper, some even go to death having erred through youthful lethargy”. Get them to work out that this useless piece of information (!) is a way of remembering: lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb) and lutetium (Lu).
For another lanthanide mnemonic and some chemistry take a look at the Nottingham University video (below) on lanthanum (there are also videos from the same series on each of the other lanthanide metals).
Hydrogen bonding
Posted on 03 September 2011 at 11:04h
The more I look critically at the IB Chemistry Diploma programme the more I find that is either simply wrong or at best only a simplified half-truth. This is not to criticise the IB programme as such as all other pre-university programmes suffer from the same problems. How aware are teachers about the truth or otherwise of some of the ‘accepted’ chemistry on the programme?
Clearly sometimes we have to give a simplified version as the mathematics is too difficult for students at this level - an example of this is describing ethyne as containing two pi bonds at right angles to each other. Other times the models used contain so many flaws that they are wrong even though both students and teachers should be very much aware of the errors. For example, the way in which ionic bonding is often taught. Other areas are less clear cut. Hydrogen bonding falls into one of these less clear cut areas.
Students are taught that hydrogen bonding occurs when hydrogen is directly bonded to one of the three most electronegative atoms, fluorine, oxygen and nitrogen. In a sense fluorine is not so important as there is only one possible compound, hydrogen fluoride, HF. Hydrogen bonded directly to oxygen and nitrogen provides many important examples of hydrogen bonding such as the anomalous behaviour of water (left) and the ‘glue’ holding the double helices together in DNA. However a critical look at this ‘definition’ causes a problem straightaway. According to Table 7 in the IB Chemistry Data Booklet chlorine (3.2) is more electronegative than nitrogen (3.0) and bromine (3.0) has the same value so hydrogen bonded to chlorine or bromine should also show hydrogen bonding. Yet in the classic graph of the boiling points of the hydrides for groups 4,5,6 and 7 (below) only the abnormally high boiling points of water, ammonia and hydrogen fluoride are highlighted as being due to hydrogen bonding.
In fact hydrogen bonding is just a more extreme case of dipole-dipole interactions between molecules. A normal van der Waals’ type of attraction between non-polar molecules is in the order of 1 kJ mol-1, dipole-dipole interactions are a little more than this and hydrogen bonding can vary between about 10 - 25 kJ mol-1. IUPAC have this year (2011) changed their definition of what constitutes a hydrogen bond thus rendering our text books somewhat obsolete. This change, which was published in Pure and Applied Chemistry, 2011, Vol 83, No. 8, p 1637-1641, bases the definition on theoretical and experimental evidence obtained during the past century. The full text can be read as a pdf file. The new definition is “The hydrogen bond is an attractive interaction between a hydrogen atom from a molecule or a molecular fragment X–H in which X is more electronegative than H, and an atom or a group of atoms in the same or a different molecule, in which there is evidence of bond formation”. This clearly still includes hydrogen bonded directly to fluorine, oxygen and nitrogen but now it also includes, for example, hydrogen bonded directly to carbon. This bond at IB level is usually considered to be non-polar but carbon (2.6) is more electronegative than hydrogen (2.2) so the bond is in fact polar. For an intermolecular force to be classified as a hydrogen bond it has to meet certain experimental conditions which are listed in detail in the article. These include, bond angles, infrared absorptions and NMR shifts.
Probably this is another example where books and pre-university syllabi will stick with the simplified version, i.e. with the ‘hydrogen bonded directly to fluorine, oxygen and nitrogen’ definition, and yet teachers should be aware that it is nowhere near this simple in reality.
Bodyscanners
Posted on 29 August 2011 at 17:27h
I suppose we have all felt like Loukai Phillips at times as we go through airport security. Loukai was so fed up with being body searched that she decided to take matters into her own hands and stripped naked in front of security staff at Bermuda airport. However many people are now ‘virtually stripped naked’ even though they may not realise it each time they go through a body scanner.
In topic 2.3 the Assessment statement is “Describe the electromagnetic spectrum”. To make this more relevant to students you could describe briefly how body scanners work as there are in fact two main methods in use which use very different regions of the electromagnetic spectrum. One uses ‘back scatter X-rays’. These provide a two-dimensional image by detecting the scatter patterns of the ionising radiation reflected from the body. In airport scanners one image is taken of the front of the passenger and one of the back. The use of image enhancing software enables airport security staff to see a virtual image of the passenger beneath their clothing with the hope that objects such as weapons, explosives and drugs are revealed. Although X-rays are used it is claimed that the dose received by the passenger is less than that received during two minutes of flying and is virtually harmless.
The second type of body scanner uses even less harmful rays. These are known as millimetre wavescanners and may be passive or active. Both use radiation in the radio frequency (just below the tetrahertz region where the wavelength is between 0.10 mm and 1.0 mm). Passive scanners record only the raw energy that is emitted from the body (or concealed objects) and direct no energy at the passenger. In active scanners the radiation is transmitted from two antennae as they rotate around the body. This is the system in use at Schipol Airport in Amsterdam and some other EU airports. Like the back scatter X-ray system it allows screeners to see the surface of the skin beneath the clothing. Some individuals and organisations have complained that it is a breach of privacy and in the case of passengers under the age of 18 there is concern that it could contravening the UK Children’s Act by producing indecent images of minors.
Demonstration of airport scanner
A novel use for biscuits
Posted on 08 August 2011 at 19:11h
In an earlier blog about the winners of the 2010 Nobel Prize for Physics I explained how Andre Geim and Konstantin Novoselov discovered graphene using very simple equipment – essentially some sticky tape and a pencil. Graphene is a single layer of graphite which is literally one carbon atom thick. It is about one hundred times stronger than steel and a better electrical conductor than copper. It is thought that it can replace silicon in transistors and find uses in touch screens and solar cells for example.
Now scientists from Rice University in the USA have shown that it is easy to make graphene from almost anything that contains carbon, for example food, insects and waste. A graduate student was explaining this to a group of Girl Scouts and said that it could even be made from their special Girl Scout biscuits. One of the scouts challenged him to do it. The graduate student, Gedung Ruan together with another student Zhengzong Sun invited the Girl Scouts to watch the process at the Smalley Institute for Nanoscale Science and Technology. They showed how high quality graphene could be made from the biscuits (as well as grass, plastics and even the dog faeces which were provided by their lab manager’s dog called Sid Vicious!). The process uses carbon deposition on copper foil. The graphene forms on the opposite side of the foil as the solid carbon sources decompose after fifteen minutes in a furnace at 1050 oC in an argon/hydrogen atmosphere.
The process produced a sheet of graphene with an area nearly the size of thirty football pitches. Zhengzong Sun estimated that with each two-inch square piece of graphene worth US$250 it would turn in a US$15 billion profit on the original purchase price of the biscuits. The serious point is that cost of producing graphene is now very low and this means that it will be more readily available for further research into its potential benefits such as for use in flat-panel and touch-screen displays, solar cells and LED lighting.
The chemists from Rice University have posted a video of the process on You Tube.
Teaching with ketamine
Posted on 24 July 2011 at 17:18h
Avid subscribers to this website will have looked at the pages on using the IB Data Booklet creatively to give them ideas as to how they can enhance their teaching of some of the concepts contained in the assessment statements. Students like to relate chemistry to ‘real life’ and by stimulating their interest they can understand fundamental concepts more easily. It also prepares them for Objective 3 type questions in the final examination which requires them to think rather than just regurgitate assessments statements and teacher’s notes from the guide.
News items can also generate great material for teaching ideas and help you connect with your students while also increasing their understanding. Recently the BBC put out an article about how the use of ketamine as a recreational drug has increased over the past decade. This was forcibly brought home by a report today which claimed that Amy Winehouse bought ketamine (along with cocaine and ecstasy) in the hours leading up to her untimely death. So what is ketamine?
A quick look on the Internet will give both its formula and some background information. It was originally developed as an anaesthetic and was used by surgeons on the battlefields of the Vietnam war in the 1960s. Mostly now it is used in animal surgery (particularly with horses) but since the 1970 it has also been used as a recreational drug by clubbers.
Although pure ketamine is a liquid it is available in powdered form as its hydrochloride salt (see image on left) and so is sometimes confused with cocaine and crystal methamphetamine. It is said that its hallucinogenic effects can range from rapture to paranoia to boredom.
Its IUPAC chemical name is 2-(2-chlorophenyl)-2-(methylamino)cyclohexanone. So how can it be used in teaching?
All the groups it contains are listed in the HL programme (assessment statements10.1 and 20.1) so we could start by getting students to build up the molecule from its name.
1. Get them first to draw cyclohexanone and then identify the second carbon atom.
2. Place a methylamino group on the second carbon atom (to form a secondary amine).
cyclohexanone structure.jpg)
3. Then place a 2-chlorophenyl group also on the second carbon atom to give the required structure.
ketamine
You can then get them to build a model (or show them a '3-D' representation) of the structure.
The molecule possesses several interesting features which illustrate important points on the IB Chemistry syllabus.
1. Polarity. Would your students expect the molecule to be soluble in water or fats? In fact it is slightly soluble in water due to the possibility of the hydrogen atom on the secondary amine forming some hydrogen bonding with water molecules – however it is essentially a not very polar molecule and is much more soluble in non-polar solvents.
2. Given that it is not very soluble in water how can its solubility be increased? It is a secondary amine which means that it is basic. Assessment statement G.8.3 covers this. By converting the molecule into its hydrochloride salt (the white powder used by clubbers) it can be made much more polar. This is similar to the examples on the syllabus of morphine and fluoxetine and are also covered under assessment statement D.9.4 - Discuss how the polarity of a molecule can be modified to increase its aqueous solubility and how this facilitates its distribution around the body.
3. It contains a ketone group. You could ask your students to give the equation for its reaction with 2,4-dinitrophenylhydrazine (G.4.1) or ask them to devise a two-step synthesis to turn ketamine into a carboxylic acid with the formula:
This covers both G.2.2 (nucleophilic reaction with hydrogen cyanide) and G.2.3 (hydrolysis of cyanohydrins) and G 7.1 (reaction pathways).
4. If you are teaching option A you could ask them what characteristic peak would be seen in the IR spectrum of ketamine (A.3.2). The obvious answer being a sharp single peak in the region of 1700 – 1750 cm-1 due to the C=O bond absorption .
5. Ketamine contains a carbon atom bonded directly to a halogen atom. During a review (US) or revision (UK) of nucleophilic substitution reactions you could ask students how they would expect ketamine to react with warm dilute aqueous sodium hydroxide solution. Because the chlorine atom is bonded directly to a phenyl carbon atom this neatly covers assessment statement G.5.2 - Describe and explain the relative rates of hydrolysis of benzene compounds halogenated in the ring and in the side chain.
6. Ketamine is also interesting as it is a chiral molecule so an obvious question would be to get the students to identify the asymmetric carbon atom within the molecule.
One way to represent the two different enantiomers of ketamine
This covers assessment statement 20.6.5 and you could go on to ask about how the properties of the two enantiomers might differ (D.8.2 ) and how they could be distinguished (20.6.6).
A lot of good IB chemistry contained in one small molecule!
Getting hold of chemicals
Posted on 10 July 2011 at 21:26h
Those of you who have read ‘Uncle Tungsten’ by Oliver Sachs will know that once it was easy to get hold of almost any chemical that a budding young chemist might want to experiment with. When I was about aged ten I was the proud owner of a Lotts Chemistry Set and performed many an experiment in my bedroom or kitchen – adding acid to iron(II) sulfide, FeS, was one of the favourites. My dentist even gave me a test-tube full of mercury to play with! Now that the dangers of certain chemicals have been recognised, Health and Safety regulations sensibly dictate what can be purchased by members of the general public. It is definitely not a good idea to let young people play with mercury (although it doesn’t seem to have done me much harm!) or buy concentrated sulfuric acid etc.and chemistry sets containing any 'real' chemicals have disappeared from toy shops. However I recently discovered that even some relatively harmless chemicals can also now be difficult to get hold of although their sale is not banned or illegal. One such example is citric acid.
At this time of year many people make elderflower cordial. This is easy to make and a good recipe to use is:
1 litre water
1.5 kg sugar
1 sliced lemon
75 g citric acid
20 elderflower heads
Boil the water, add sugar and lemon, remove from heat while sugar dissolves, then reboil. Add citric acid and flower heads. Leave to cool, strain then bottle.
There is just one problem. You cannot easily buy citric acid anymore even though it is present in many citrus fruits such as lemons.
Citric acid (2-hydroxypropane-1,2,3-tricarboxylic acid) is usually sold as its monohydrate (which can be converted to its anhydrous form if it is heated above 78 oC). It is a weak acid and acts as a preservative. All my local pharmacies no longer sell it to the general public as it is used by addicts to cut their heroin (it actually works as a buffer and increases the solubility of heroin in water). Luckily a shop in my local market which sells equipment and substances for home brewers does stock it. If you can convince them why you want to buy it then they produce a package from under the counter! Whilst talking to one of the pharmacists I also discovered that they do not sell the tried and tested old fashioned diarrhoea mixture ‘kaolin and morphine’ any more. Again this is due to addicts who allow it to stand to precipitate the kaolin then they concentrate the liquid to extract the very small amount of morphine present. The threat of terrorism has also put paid to the ready availability of certain chemicals. Try buying hydrogen peroxide in any strength after it was used by the shoe-bomber. Similarly getting rid of persistent weeds in the garden is now much harder. Sodium or potassium chlorate are very effective weed killers (the weeds mistake the chlorate ion for the nitrate ion) but because they are also used in home-made bombs they are now impossible to get hold of in any quantity. At this rate all that will be left for budding young chemists to experiment with will be simulations.
'Chemistry man'
Posted on 03 July 2011 at 12:54h
I’ve been running a Chemistry workshop in Astana for this past week. The aim was to give examples of good practice to teach ‘the IB way’ rather than cover the IB in specific detail. The teachers came from schools all over Kazakhstan where they are trying to modernise their education so that it measures up to international standards whilst still retaining their unique Kazakh culture. At the same time my colleague Birgit Jennings, a former Chief Examiner, was running a similar workshop for the Visual Arts. For the whole of one afternoon we put the Chemistry and Visual Arts participants together. This is something we have done at previous workshops and have published in IB World (November 2002 page 20).
.JPG "'Chemistry man'")
One of the 'products' of the afternoon
Although the sessions are meant to be fun there is a very serious point to the exercise. The reason for combining the participants is to help them to understand how their subject can relate to other subjects in the IB ‘Hexagon’. The students they teach will be exposed to solving problems in subjects in all the five other groups so it is good for the teachers to also understand this so that they can incorporate it into their teaching. After a short presentation - looking at how Chemistry and the Visual Arts have been related throughout history – the participants working in groups were asked to first list the qualities they saw as essential for Artists and Chemists and then compare whether they were the same or different. They were then asked to devise a set of common criteria for assessment. Finally they were asked to create a work of Scientific and Artistic merit, present it to their colleagues and explain its significance then assess it according to the criteria they had devised. The day before we had been shopping in a local Astana supermarket to buy everyday products. This provided the participants with all the materials available for them to use.
.jpg "Working on the qualities and criteria")
jpg.jpg "Teachers from Kazakhstan working on making a product with scientific and artistic merit")
Working on the qualities and the criteria Working on making the product
We were really pleased with how the sessions went. Interestingly the participants found that that the qualities required for a good artist are almost exactly the same as those for a good chemist. These include:
- Passion for subject
- Open-mindedness
- Imagination
- Risk-taking
- Skills of observation, knowledge, techniques, experimentation and analysis
- Ability to think laterally
- Hardworking and conscientious
- Perseverance
- Curiosity
- Critical thinking
- Patience
After reporting back and discussing what each group had suggested the five criteria upon which work should be assessed (each worth 4 marks to give a total of 20) were:
1. Research skills
2. Creativity/originality
3. Technical skills
4. Perseverance
5. Quality of product
Although the real value of the exercise was on the process rather than the product (in a similar fashion to the Group 4 Project) the four groups all produced interesting outcomes. One produced a working volcano (using baking powder and vinegar to produce the eruption). Another produced several working items along the theme of energy including a hot air balloon and another produced a family to represent healthy living and attention to the environment. Our favourite was ‘chemistry man’. What I particularly liked about it was the tear in his eye to show his emotion at having made a major discovery – a nice way to bring in TOK by showing emotion as a ‘way of knowing’ in Chemistry.
Falling life expectancy
Posted on 23 June 2011 at 21:37h
Chemistry often gets a bad press. Some obvious examples are environmental pollution such as the Deepwater Horizon oil spill, the use of toxic defoliants such as Agent Orange or the siting of nuclear power plants in Earthquake zones such as in Fukushima, Japan. Those of you who have read the first chapter of my Chemistry Course Companion will know that I counter this by looking at the very large increase in life expectancy during the past century. This is very much down to chemists who have provided the means for providing safe drinking water and synthesised antibiotics and other drugs to treat major illnesses and diseases etc. In fact the general public now seem to take it for granted that life expectancy will continue to rise. In the West in particular this is causing problems with ageing populations.
The governments of many countries are increasing the retirement age and also increasing the contributions that workers have to make in order to try to fund the projected pensions of future retirees. This is seen as a big problem because ‘people are living longer and will spend many years in retirement’. Many workers are unhappy with their governments’ actions and are taking strike action. What no-one seems to question is the underlying assumption that life expectancy will continue to rise. For some time I have felt that this may not actually be the case. Whilst some individuals may well have a long and healthy life for many others the story may be very different. Obesity in many countries is now a major issue and coupled with a sedentary lifestyle, increasing exposure to pollutants (particularly secondary pollutants from photochemical smog) and alcohol and substance abuse it may well be that the next generation will not actually live as long as the current generation unless there is a huge change in lifestyle. This is now borne out in fact. A recent study by a team from the University of Washington has shown that there are now large variations in life expectancy within the different counties in the United States. For men it varies from 65.9 to 81.1 years and for women from 73.5 to 86.0 years. More significantly between 2000 and 2007 80% (men) and 91% (women) of American counties fell in standing against the international life expectancy standard. Put another way American citizens who have among the highest standard of living in the world are losing out on life expectancy compared to other countries. As chemistry teachers we need to educate our students to use the benefits that chemistry can bring wisely and not abuse all the undoubted advantages that a high standard of living can bring.
Added later: 11 July 2011. I've just read an interesting article by Eric Reiter, S, Jay Olshanskey and Yang Yang published in Health Affairs published after I wrote the blog above which confirms this. They have used a new way of predicting mortality rates by using current statistics on cadiovascular death rates caused by obesity in the 25-29 age range and extrapolating it to older people and have reached exactly the same conclusion that life expectancy in the US is set to fall.
Added even later: 8 May 2012. Today I received a nice e-mail from June Owensboro who works as a Staff Researcher/Part-time Writer for TremLifeInsurance in the USA. She came across this blog whilst she was researching for information to write an article on life expectancy and found it helpful for her research. Her article on Popular Ways of Increasing Life Expectancy looks at what you as an individual can do to boost your chances of living longer - so if you want to buck the trend and live a long life it is well worth spending some time looking at it!
IB May Chemistry exams
Posted on 15 June 2011 at 16:48h
The two May IB Chemistry exams (TZ1 and TZ2) have recently been sat and marked and the results are eagerly awaited. Teachers were encouraged to complete G2 forms to comment on these exams but as these went directly to the IB for consideration during the Grade Award Meeting in Cardiff they are confidential. However several teachers have also given their comments on the OCC. There was one comment that stood out for me.
Generally teachers tend to make negative (although often constructive) comments but this year there is one that pleased me as it is so positive. The teacher liked the Data Response Question on Time Zone 2 Paper 2 (both SL and HL). The question gave some raw data about an enthalpy experiment and students effectively were asked to use Hess’s Law to calculate the enthalpy of hydration of anhydrous copper(II) sulfate, CuSO4, to give the solid pentahydrate, CuSO4.5H2O.
Anhydrous copper(II) sulfate, CuSO4.
Completely white or slightly blue due to absorbing water from the atmosphere?
In the raw data one of the observations made was that the anhydrous copper(II) sulfate used (which should be a pure white solid) appeared slightly blue. The last part of the question asked students to evaluate their result and suggest improvements. What was wanted was that the copper(II) sulfate may already have absorbed some water from the atmosphere so it might be a good idea to dry it in an oven first to drive off any absorbed water. The comment on the OCC liked this and said it provided a good example to show to students to help them when they come to evaluate their practicals. Those of you who are astute will see that this example has actually been given on this website for some time as a marked practical under the heading of Hess’s law in Marked Practicals. Why I approve of the comment is that I think exams should also be about educating students as well as testing them.
There was a second comment (which was more typical) about whether the variation of carbon dioxide in the atmosphere due to seasonable changes should be asked as it is not specified on the syllabus. This is very similar to a complaint made by a teacher about a question on the November 2010 paper (P2 HL and SL Question 3) which asked why a very low pressure is required in a mass spectrometer. Assignment statement 2.2.1 states “Describe and explain the operation of a mass spectrometer” which is clearly Objective 3. The teacher’s notes however mention vaporisation, ionization, acceleration, deflection and detection but do not specifically talk about low pressure. The teacher’s comment on the OCC was, 'How would we know to prepare students for something like this? This sort of thing drives me crazy as it seems like the kind of thing that pushes to introduce a haze of random information only loosely connected to the syllabus.' I think this raises an important point. The syllabus does not start on p41 of the guide. The Aims and Objectives of the subject are also important. Objectives 1 and 2 test what students know and this should be clearly stated on the syllabus. Objective 3 tests what the student understands. The Assessment statement covers this in ‘Explain the operation of a mass spectrometer’. If a student understands the underlying theory then Objective 3 should be testing whether they can use this theory to deduce something reasonable. If all the deductions are listed in the teacher’s notes and they simply repeat what they have learned then they are only really being tested on Objectives 1 and 2 despite the fact that the command term used may be an Objective 3 command term. A similar argument can be made for the variation in carbon dioxide in the atmosphere which appeared on the May paper. Assessment statements E.3.2 and E.3.3 which are concerned with carbon dioxide and the Greenhouse Effect are both Objective 3.
In future exams more of the Objective 3 questions will be genuine Objective 3 questions. That is, questions in which they will have to think rather than just remember. This will bring the IB more into line with A level and pre-U exams where 30% and 40% of the marks respectively are of the IB Objective 3 type whereas in the IB it is currently only 28%.
Cows' farts
Posted on 12 June 2011 at 16:50h
A past Paper 3 question for Option E : Environmental chemistry asked students to identify a natural source of methane. Several students gave the journalistic answer “cows' farts” which earned them zero marks. To gain the marks the answer needed to include mention of the anaerobic decomposition of organic material.
In fact grazing animals such as cows are thought to account for around one fifth of the total global emission of the greenhouse gas methane but the precise amount is difficult to quantify. Researchers from the University of Bristol in the UK have recently been trying to use a marker to estimate the exact amount. In a recent article published in Animal Feed Science and Technology they have been looking for the presence of archaeol (see below) which is produced by the symbiotic or 'friendly' microbes that live in the foregut of ruminant animals. These organisms are called archaea and they produce methane as a by-product of their metabolism which is then released by the animal as burping and flatulence.
Structure of archaeol
What the researchers have shown is that cows fed on grass silage require less feed but form more archaeol and emit almost twice as much methane compared to cows fed on a concentrate based diet. This work confirms that manipulating the diet of cows may be one important way of controlling the emission of greenhouse gases.
Chemical passwords
Posted on 28 May 2011 at 15:04h
The very fact that you are reading this tends to suggest that you use the Internet a lot. One of the frustrating things that I find is that I am often required to give a username and a password to access particular sites – particularly those that would like me to part with my money!
The username is easy but what to do for the password? Many people simply use the same password for all sites as it is easy to remember. The problem with this is that like PIN numbers once the security is breached then it puts all the accounts in jeopardy. There have been many examples of this particularly when people use the same password for sites such as Twitter and Facebook.
If you are responsible and use a different password for each site then the problem is that you cannot possibly remember them all correctly so they end up getting written down which again compromises security. I recently forgot a password and the computer-generated one that was sent to my e-mail account after I requested it was 6xo7g5nNp8. Clearly this is not something I am going to carry in my head and so as usual I was asked if I wanted to change it to one of my choosing. Like most strong passwords this must contain at least six characters and be a mixture of lower and upper case letters and contain at least one number.
At last I have found an everyday practical use for all that Chemistry you teach in school!!
Most organic compounds such as glucose, C6H12O6 are not going to be any good as they do not contain lower case letters but ionic salts are a gift in terms of being able to remember them easily (as you only need to remember just two or maybe three words e.g. zinc nitrate or hydrated copper sulfate).
Here are just a few of the thousands that you could use:
ZnNO32, CuSO45H2O, NaCH3COO, MgSO47H2O (Epsom salts) and IrCOPPh32Cl (Vaska’s complex)
Make up your own from your favourite chemical and you need never write down or forget a password again.
Alcohol in the body
Posted on 19 May 2011 at 12:20h
Many people’s jobs (e.g. health workers and airline pilots) depend on the fact that they abstain from taking alcohol. The chemistry behind the common methods used to determine the amount of alcohol in the blood, urine and breath are covered in Option D: Medicines and drugs under Assessment statement D.4.3 . These include the reduction of the orange dichromate(VI) ion to the green chromium(III) ion used in the ‘blow in the bag’ and the use of infrared and fuel cells in different types of intoximeters.
The amount of alcohol present in alcoholic drinks is usually listed clearly on the label on the can or bottle. However alcohol can be imbibed unintentionally in other ways apart from drinking alcoholic drinks. For example, certain mouth washes, gripe water for infants (see left), hand washing gels, hairsprays and cosmetics can all contain ethanol. All of these can boost the amount of alcohol in the body and lead to positive results even if the person in question has not been drinking alcohol as such. Researchers at the University of Florida have been looking at another way of determining alcohol body content by examining the breakdown products in urine. The two breakdown products in particular are ethyl glucuronide (EtG) and ethyl sulfate (EtS). 
They have shown that non-drinkers who clean their hands regularly using hand sanitisers showed levels of ethyl glucuronide in their urine consistent with alcohol drinkers. However the level of ethyl sulfate was considerably lower. They hope this difference in the levels of the two chemicals may lead to a more reliable test to distinguish between those who have imbibed alcohol and those who have absorbed it through their skin and thus prevent false positive tests and the potentially very damaging wrongful charge of alcohol abuse.
A video
detailing this has been produced by the University of Florida.
Isocyanic acid
Posted on 17 May 2011 at 20:23h
When we breathe in smoke from a wood fire we may be breathing in toxic amounts of isocyanic acid. Isocyanic acid is the simplest molecule to contain all four of the most common elements in organic compounds. It has the formula HNCO and was first discovered by Wohler in 1830.
Using a specially designed mass spectrometer to measure gases in the atmosphere researchers from the University of Colorado have reported that isocyanic acid is produced in the smoke from biomass fires. Initially they detected it in controlled fires in a laboratory where the amount was up to 600 parts per billion by volume (ppbv). However they were also able to show that it was produced during the recent forest wild fires that occurred near Boulder, Colorado. What surprised them was not only that it was present in the smoke but it was also detected in the atmosphere several miles away. They have also found isocyanic acid in the urban atmosphere in Los Angeles and the level is higher during the day suggesting that it may be formed as a secondary pollutant in photochemical smogs (see Option E, Assessment statement E.10.2 ). Isocyanic acid has also been detected in tobacco smoke (relevant for Option D, Assessment statement , D.5.3).
Isocyanic acid is known to be toxic to humans. It is soluble in blood and if levels exceed 1 pppv then it may contribute to health problems such as cardiovascular disease and arthritis. Isocyanic acid is related chemically to methyl isocyanate, the compound that caused the deaths in the Bhopal tragedy (see separate blog on Chemistry and politics). The team at Colorado University have produced the following video on isocyanic acid in smoke
.
Tech-savvy generation
Posted on 12 May 2011 at 14:35h
I wonder how many teachers are taking on board the quantum shift that has occurred during the past fifteen or so years that has completely changed the way a whole generation communicates. Most of the students in an IB Diploma class cannot remember pre-Facebook/Twitter days. They have grown up in a digital world and are totally accustomed to instant communication and multi-communication (e.g. watching a video clip, listening to music and surfing the Internet simultaneously). When I worked in India a few decades ago I was basically reliant on the postal system for my inter-country communication. To be fair to the Indians the service was excellent – I once got a letter brought to me in the Himalayas one day’s journey away from a road that had been posted in the UK two days earlier! – but, it was hardly instant. Now using my i-phone I have the choice of whether to phone at relatively low cost or use VOI (Skype) linked through wifi for free to call a colleague easily and effortlessly anywhere in the world. There are clearly wonderful advantages, such as making links with schools, teachers and students in different continents let alone just different countries. This whole Chemistry InThinking website assumes that short video clips will be used regularly and links are made to a vast amount of virtual, instant information. Unfortunately there are downsides to this instant world of communication too.
This generation of students finds it much harder to concentrate on any one topic for more than a relatively short space of time. To capture their attention so that their mind does not wander for a whole hour is an immense challenge to a teacher – students are simply not wired in to this approach as it is alien to the whole way in which the rest of their life operates. When I observe a teacher with a laptop class (whether the class is made up of IB students or IB teachers in a workshop) it is noticeable how many are surfing the web or e-mailing at the same time as they are listening (or pretending to listen) to the teacher or workshop leader. Some teachers have banned the use of laptops and mobile phones in the class for this reason but surely a better solution is to embrace the technology. What we need to do is encourage students to be selective in their use. It can liberate us from the drudgery of providing all the factual information as the facts are all ‘out there’ anyway. We should be concentrating on helping them to understand the underlying concepts and use the technology to best advantage. In other words, we should be training them in how to use the facts discerningly and how to apply their knowledge to solve problems in unfamiliar situations.
A nice example of this can be found in the work being done on the importance of protein structures (covered in Topic B2 in the IB Human biochemistry option) by Professor James Hinton at the University of Arkansas in Fayetteville. This is described in an article in Science Nation
which also includes the following video.
There are many programmes that show the 3-D structure of proteins using computer (laptop) screens in so-called 3-D. However they are still displayed on a 2-D screen so the 3-D is an illusion and students do not gain a true understanding. When I cover ‘Shapes of simple molecules and ions’ in Topics 4 and 14 I know that ‘3-D’ images on a laptop (which superficially look good as they rotate - see the video above) are not really that helpful. Students have a much better grasp of the structure and shape of simple molecules if they can physically make and handle real 3-D models using kits such as MOLYMOD®. What Hinton has done is make his virtual images genuinely 3-D using 3-D glasses1 so that students can ‘walk inside’ proteins and begin to grasp at first hand the importance of the three-dimensional structure to the way in which proteins function.
13-D glasses have been around since Victorian times so combining them with modern computer screen images is a nice example of an extension to the technology of earlier generations. They were used in WW11 to locate the site of German V1 and V2 rockets. By taking and aligning photographs scientists in Britain were able to see the landscape in 3-D which showed up where the sites were being built. This use of 3-D probably saved the lives of thousands of people.
Hookah pipes
Posted on 30 April 2011 at 12:40h
I’ve never believed that teachers should tell their students how to live their lives outside of the school premises although hopefully we can certainly influence them by setting an example as good role models. We do however have the responsibility to inform them so that they can make their own choices and decisions. Within Chemistry this may be linked with ‘Aim 8’ issues which include an ethical dimension and sometimes the syllabus itself contains an explicit reference to such issues. For example Assessment Statement D.5.3 in Option D – Medicines and drugs states “Discuss the short- and long-term effects of nicotine consumption” and D.10.3 states “Discuss the arguments for and against the legalization of cannabis.”
I’m currently en-route to Kazakhstan where arguably they are importing my knowledge of western education (see my earlier blog on “How 'International' is IB Chemistry?”). The East however is exporting part of its own culture to the west. There has been a marked increase recently in the use of the hookah by students in Western countries. Hookah pipes go by several names such as shisha, narghile, galyan, water-pipe or hubble-bubble pipe but essentially they all work in similar fashion. Tobacco is heated by coal or charcoal in a bowl and the smoke is passed through water where it is ‘purified’ and cooled before entering the pipe where it is smoked. Part of the attraction of the hookah is that smoking it can be a very sociable experience. The pipe may be passed round or several pipes may come from the same hookah (see left). One of the other often quoted advantages is that as the smoke passes through water many of the harmful substances are absorbed by the water in the ‘purification’ process so that it is a lot less harmful to health than smoking cigarettes. However there is strong evidence that this is not true. Smoking a hookah can significantly increase the risk of developing lung cancer, respiratory illness and heart disease as well as causing pregnant mothers to give birth to babies with a low birth-weight.
What is alarming is the result of a recent study by researchers from The University of New York at Buffalo published in Biomedical Health Central Public Health. As perhaps might be expected the prevalence of hookah smoking by young people is high in Middle Eastern countries (for example, 5-6% of pregnant women smoke the hookah in Lebanon) but this study also shows that hookah smoking among school-aged students is increasing in Western countries such as the United States and Estonia. In other Western Countries such as the United Kingdom it is also popular among university students. Most, but not all, of these young people smoking the hookah are of Middle Eastern origin. In the US students as young as 13 have been reported as regular users.
Simply telling students that smoking a hookah is harmful to their health is unlikely to get them to take the facts on board as they believe (wrongly) that the water filters the impurities. However a more powerful approach is to get them to understand why and include the dangers of hookah pipes when covering D.5.3 and D.10.3. In addition to nicotine there are estimated to be over 400 toxic substances in tobacco smoke of which about 60 are known to cause cancer. Students can see from the structure of nicotine (right) that it is essentially non-polar and will not therefore dissolve in water to any meaningful extent. Many of the other toxic substances are hydrocarbons or aromatic tars that are also non-polar. Even the poisonous gas carbon monoxide which is slightly polar only has a solubility in water of 0.026 g dm-3 at 20 oC so much of it will not be absorbed by the hookah water. Some users also go on to smoke marijuana mixed in with tobacco using a hookah pipe in the belief that it will not harm their health so the same arguments apply.
P.S. What did surprised me is that when I visited a restaurant in Kazakhstan one of the waiters had the job of lighting all the hookah pipes for the customers. This involved him breathing in clouds of smoke from the tobacco and coals directly before it passed through the water. After having done one he then moved on to the next one and kept this up for the whole evening. Health and Safety?
IT and workshops
Posted on 15 April 2011 at 17:36h
I’ve been running IB workshops for many years – the first was in the 1980s and I have seen a lot of changes. Like all changes there are usually advantages and disadvantages. Until recently in Europe and in Latin America (the old IBLA region) workshop venues were always schools. In North America they have always favoured so called professional venues which usually means hotels. Apart for the fact that this could imply that a school is not a professional place of work (!) there are real advantages and disadvantages for both types of venue. I once spent four hours on a bus going round the Paris périférique being transported from a hotel to a school so I do appreciate that in hotel venues there is no travelling. On the other hand there is no access to laboratories in a hotel which does make including hands-on practical work in Chemistry either impossible or at the very least rather superficial. For the past three years or so ‘professional’ venues have become standard across all of the IB regions. I even did a workshop in Disneyland, Paris shortly after IBAEM switched over! Of course, the best solution of all would be to hold them in hotels but organise it so that a couple of sessions could be spent in a local IB school. On balance, however, the switch to hotels is probably a good thing. InThinking has always held its workshops in hotels and one other advantage is that InThinking sessions finish early enough for the participants to enjoy Paris, Berlin, London, Madrid or Barcelona as the hotels are always very central.
A marking session during a recent Chemistry workshop in Zurich in the Radisson Airport Hotel
One other recent change though is not so good. IT is generally an excellent tool. In Europe we insist that the workshop leader has Internet access throughout the whole workshop. Often this also means that all participants can be on line throughout the workshop too. This is essential to deliver a modern workshop that meets the needs of the syllabus and it amazes me that this is not something that is routinely provided in the IBNA region. After the first day I like to talk to my participants and ask them if they are happy with the way the workshop is running as it means that if there is a problem, for example, if their level of English is preventing good communication, then there is time to address it during the workshop. Until the IB Global Architecture for Professional Development in workshops was launched in 2009 it was normal to give all participants an evaluation form to complete and hand in at the end of the workshop. This meant that the workshop leader got instant feedback when the workshop was fresh in his or her mind and that we got 100% return from all the participants. Now the evaluation is ‘done’ electronically. Participants receive an e-mail with a form to complete a few days after the workshop has finished. Even after more than two years of this system it still does not work. I am lucky if I get responses from about half of my participants and after collating by the IB the feedback arrives anywhere from between six weeks and three months after the workshop has ended and so is virtually useless. We have gone from a 100% instant return to about a 50% return many weeks later – this is not progress. For this reason at InThinking workshops we still ask all participants to fill in an evaluation form during the last session of the workshop – it may be using the old-fashioned technology of a pen and a piece of paper but in this instance it is far superior to the fallible IT alternative.
Illiterate chemists
Posted on 10 April 2011 at 15:59h
It is that time of year again when I get to see many Extended Essays in Chemistry. Two factors stand out. One is very pleasing to see – more and more students are actually writing genuine research Essays rather than just writing up yet another practical experiment that simply follows the Internal Assessment criteria. This trend of following the IA criteria came in during the mid 2000s when the IA really took hold following the new programme for first examinations in 2003. It was responsible for students not achieving so well – not only in Chemistry, but also in Physics and Biology. During the past two years this trend has been reversed and the percentage of students gaining an A has started to go back up again. Perhaps of even more importance is that the percentage of students gaining A, B or C – i.e. writing an Extended Essay that is at least satisfactory with the opportunity to be awarded bonus points - is also increasing. I am hopeful from what I have seen so far that this trend will continue this May session.
The second point is perhaps more to be expected – many students are not really able to express themselves well using the accepted chemical language. I have written on this at length with examples in the TOK section (as language is one of the four IB ‘ways of knowing’). I suppose it is not too surprising as apart from the IUPAC convention for naming organic compounds etc. the use of correct chemical terminology is not stressed on the programme. Also students are unlikely to be penalised heavily for the wrong use of terminology provided that they can be understood. I had put this down to teachers not having enough time to stress how to write ‘good chemistry’. However now I am not so sure. Look at the following diagram of the mass spectrum of sulfur and the sentences that follow:
You might expect that I have culled this from an Extended Essay written by a student. In fact it was written by an experienced IB teacher. I was recently asked to edit some material written by two IB teachers for publication. It surprised me to find that the teachers were making many basic errors in how they express their subject. If the teachers do not know how to write good chemistry how can we expect our students to do it? Sometimes it is actually wrong but at other times it just does not follow the accepted manner of expression. This may not matter except that the IB is quite particular about the conventions it uses (most, but not all, are taken from IUPAC). Using M instead of mol dm-3 is not really wrong but it could confuse students as they will never see the use of M in an IB examination (except perhaps a specimen paper which has not gone through rigorous checking). In my page on language I make the point that perhaps when a student cannot answer a chemistry question it is not because they do not understand the chemistry but because they do not understand the language that the question is written in. The language page has many points listed but for starters next time you write a practical sheet, worksheet, some notes, a PowerPoint or a test it might just be worth checking the following.
- Elements and ions do not have capital letters (except when they start a sentence).
‘Silver nitrate solution reacts with sodium chloride solution to form a precipitate of silver chloride’ is correct. ‘Silver Nitrate solution reacts with Sodium Chloride solution to form a precipitate of Silver Chloride’ is wrong.
- Formulas should not be used on their own in sentences.
‘NaOH solution was titrated with HCl is wrong’. (HCl is a particularly bad formula to use as it could mean hydrochloric acid or hydrogen chloride). It is usually considered good practice to write the name of the chemical then, if the formula is needed, put it after the name. For example, aqueous silver ions, Ag+(aq), react with aqueous chloride ions, Cl-(aq), to form a precipitate of silver chloride, AgCl(s).
- When using state symbols do not make them subscript.
Ag+(aq) is better than Ag+(aq).
- When a compound can exist in more than one oxidation state then include the oxidation state.
Copper(I) bromide or copper(II) bromide.
-
Physical constants are written in italics. This really seems to not be widely known. If the constant is qualified then the qualification is written as a subscript but not in italics (unless it is the standard state sign in which case it is a superscript). For example, ∆H
c, pKa, E.
- Use mol dm-3 as the normal unit for concentration – not M.
- In a table where the units are given at the top (or on the axes of graphs) use the ‘slash’ notation for the units. For example, if you wish to express 10.0 s as a number then you need to divide by seconds 10.0 s/s = 10. At the top of the table it is therefore better to write time / s rather than time (s).
Hopefully you will now write better chemistry and your students will have less difficulty making sense of IB examination papers.
Vacant seats on planes
Posted on 29 March 2011 at 14:53h
March has been a hectic month for travelling. I’ve run workshops in Berlin, London (twice) and Zurich as well as set the 2011 European Baccalaureate examination in Brussels and next week I am in Italy. All this has meant a lot of flights from my local airport, Cardiff. The airline I use, KLM, rewards me for this with a Gold Elite Plus Card and frequent flyer air miles. It does make travelling a lot easier and I’ve written many of my blogs while waiting in the executive lounge in Schiphol Airport in Amsterdam. However I’m not proud of my global carbon footprint. I’m also not very sure that people who fly a lot should be rewarded for their loyalty with access to lounges and offers of subsidised flights with the air miles they have accumulated. It would actually make more environmental sense if they were taxed more heavily to offset all the emissions of carbon dioxide and oxides of nitrogen created by flying. To add to this I discovered that, since the clocks changed on Sunday, KLM have made another change which further increases the inefficiency of their flights. Everyone would like the seat next to them on a plane to be vacant but it is an added bonus when it happens by chance. Since 27 March 2011 KLM have introduced a new business class on all their European flights. Business class passengers are guaranteed that the seat next to them will be empty. Does it really make environmental (or even economic?) sense to be flying planes with guaranteed vacant seats?
Early X-rays
Posted on 17 March 2011 at 15:19h
I’ve come across three completely separate references to the early days of X-rays recently that have intrigued me. It could be argued that X-rays are not on the IB Chemistry syllabus but when teaching Topic 2: Atomic structure it is certainly worth including the work of Henry Moseley who used X-rays to show that each element is defined by a unique atomic number.
It is a well-known fact that X-rays were discovered by Wilhelm Roentgen in 1895. Roentgen was a professor of Physics in Bavaria who was exploring the path of electrical rays in a partially evacuated glass tube when he realised that rays were given off that could penetrate a number of objects. He used his own hand, and later that of his wife, to take the first X-rays of the internal structure of the body.
I was therefore surprised to find a plaque (see above) in my local hospital in Bridgend, South Wales honouring what appeared to be the discovery of X-rays as long ago as 1785. This plaque commemorates Dr William Morgan (1750–1833) and states that he constructed the first X-ray tube. This would tend to suggest that he actually discovered X-rays but the TOK part of me says that if you read it carefully he just constructed a tube that produced X-rays not that he recognised that they were present.
In an article published today in Radiology, Gerrit Kemerinck of Maastricht University in Holland has compared an X-ray machine made in 1886 with a modern machine. The old machine in Maastricht was assembled originally by a High School teacher called H.J. Hoffmans together with the director of the local hospital only a few months after Roentgen announced his discovery. This machine, which has lain in a warehouse for many years, still functions well but to obtain a comparable image to a modern machine radiation some ten times higher is needed and the image, although recognisable, is not as sharp.
This leads on to the third reference I came across. In the workshop I was running for experienced IB Chemistry teachers recently in Berlin one of the participants talked about using X-rays in the 1920s to determine how well shoes fitted. I can remember these machines well myself as their use continued into the 1960s. It used to be great fun as a kid to put your foot into one of these 'pedoscopes' (see right) and see all the bones in your feet. Parent would stress how useful these machines were as having properly fitting shoes would ensure that their children’s feet were less likely to suffer problems in the future. It is a good example of how people use 'current' scientific knowledge with the very best of intentions without realising the possible potential for damage. Later, of course, the machines were banned when it was realised the harm that repeated exposure to X-rays can cause.
Diamond chemotherapy
Posted on 13 March 2011 at 19:59h
One of the things I enjoy doing is making links between the different topics in Chemistry and treating Chemistry holistically rather than taking a modular approach. A nice example which encompasses nanotechnology, catalysis, organic chemistry, acids and bases, nucleic acids and medicines and drugs has just been reported.
One of the most common drugs administered as part of chemotherapy is doxorubicin. This compound is an antibiotic which was first obtained by mutating a strain of the bacterium Streptomyces peucetius. It functions by binding to DNA and preventing nucleic acids from replicating and thus preventing cell division.
It is known as an anthracycline and has the chemical formula:
You could ask students to identify the functional groups in a molecule of doxorubicin. These would include ketone, hydroxyl (alcohol), ether and amine as well as aromatic rings. It will have some polarity due to the many –OH groups but it is administered in an ionic form as its hydrochloride salt (the amine becomes protonated by the hydrochloric acid) to increase its solubility in an aqueous medium.
Doxorubicin is given to treat many different types of cancer including cancer of the breast, ovaries, lymph glands and the thyroid. There are however several problems with administering doxorubicin. It is required in relatively large doses and can cause quite serious side-effects such as cardiac problems as well as nausea and hair loss. This relates well to the benefit to risk ratio and to the concept of therapeutic window in Option D.
A more efficient way of delivering much smaller doses of doxorubicin has been developed by a team at Northwestern University. In an article published in Science Translational Medicine they report how they have reversibly bound doxorubicin to nanodiamonds. The nanodiamonds are thought to act as a surface catalyst and the doxorubicin remains in the body ten times longer. Currently this has only been tested in mice but the doxorubicin has been shown to be much more effective when it is delivered in this way and less toxic. Nanodiamonds have the characteristic diamond structure but are only 2 to 20 nanometres in diameter. They are found in the detonation products from explosions and are also present in some meteorites. They are being increasingly used in research in living systems as they show antioxidant and anti-inflammatory properties. It is thought that certain biologically important molecules interact with the surface of the nanodiamonds and it is this which led to the research with doxorubicin.
Perfect cup of coffee
Posted on 09 March 2011 at 20:27h
If you are like me, you can’t teach until you’ve had that first cup of coffee in the morning. I was lucky where I worked as Val, my technician, used to bring me a freshly brewed cup just as my first class was starting at 8 o clock every day.
At the moment I am being inundated with Extended Essays to mark as the deadline for them to be with the examiner is 15 March. One of the perennial favourite topics for Chemistry Extended Essays is something along the lines of ‘What is the best way to make a cup of coffee?’ and the students analyse the amount of caffeine obtained from different types of coffee and/or the different ways of preparing a cup of coffee. I’ve just read an article in Scientific American which relates how Rich Nieto, the co-owner of a coffee bar in Queens has perfected the art of making good coffee. The article, written by Summer Ash, explains how he has followed the scientific method and tested all the variables to produce the perfect cup.
Next time one of your students wants to do their Extended Essay on caffeine just refer them to this article.
Cannabis & mental illness
Posted on 02 March 2011 at 14:26h
Should the use of cannabis be legalised? Assessment statement D.10.3 in the Medicines and Drugs option asks students to discuss the arguments for and against the legalisation of cannabis. The teacher’s notes given alongside the statement are not that helpful and in fact some of the arguments often given are not really specific to cannabis. For example, because cannabis is often imbibed through smoking, arguments about causing damage to the lungs and increased likelihood of cancer etc. are given even though they more accurately refer to nicotine and the products of combustion of tobacco leaf. Similarly the argument that taking cannabis leads on to taking harder drugs is not really about cannabis as such but any illegal drug. There is some sound research that cannabis can give relief for certain diseases which is an argument for legalising it but the counter argument often given is that taking cannabis can lead to mental illness. Opponents of this argument often say that there is no real evidence to support it – perhaps people who already have a mental illness are more likely to be cannabis users, i.e. which triggers which?. A recent study published in the British Medical Journal does now support the argument that taking cannabis does cause psychotic disorders such as schizophrenia.
A group of researchers from Germany, The Netherlands, Switzerland and the U.K. studied a group of 1,923 young people between the ages of 14 and 24. They were carefully screened beforehand to ensure they had no previous diagnosis of psychotic disorders and were initially reported to be non-cannabis users. Over a ten year period they were monitored for both cannabis use and psychotic disorders. The findings showed that taking cannabis significantly increased the risk of developing psychotic disorders. The study did determine that social factors and the taking of other sorts of drugs did not appear to be significant but did not determine whether the stronger types of cannabis (i.e. skunk) caused more disorders than the milder cannabis resin or marijuana.
Electronic marking
Posted on 25 February 2011 at 22:11h
The days of physically sending scripts etc. half way (or indeed all the way) around the world are numbered. In May this year the IB is introducing e-marking for the first time in Chemistry. Scripts will be sent to a central base, scanned and then sent digitally to assistant examiners. In May this year e-marking will be limited initially to Paper 2 - Paper 3 will still be marked the old way.
The only obvious difference that the students will see is that whereas before they had one or more (dotted) lines in which to write their answers, these lines will now be encased in a box.
To illustrate how this will work, last year’s paper has been put on the OCC formatted with the new changes. Some of the problems that the system will need to be able to cope with are how to deal with the student who writes outside the box or continues to answer the question on an attached separate piece of paper.
There are clear advantages to e-marking. The most obvious being the cost – both economic and environmental. In future examiners may well mark just one or two questions, not the whole school and moderation will take place during this marking as they must mark within the same range as the Principal examiner who will have already marked a few of the boxes unbeknown to the assistant examiner. If the assistant examiner’s marks do not lie within this range their marking will not count and the boxes remarked by someone whose marking is in accordance with the standard set by the Principal examiner. This should help to ensure a more uniform standard of marking and eliminate bias as different questions from the same student will be marked by different examiners.
However there are some disadvantages and care will be needed to ensure that candidates (and schools) are not disadvantaged. For example, several boxes will need to be ‘lumped together’ so that 'Error Carried Forward' can be used correctly. Care will be needed to avoid penalising candidates more than once on the whole paper for incorrect use of significant figures and units. Also, by not marking all the papers (and questions) from one school, examiners will not be so aware of schools with problems and it may be harder to spot cases of plagiarism or other forms of cheating. Candidates and schools also need faith in the system that all the marked boxes will be properly correlated. An example of what can go wrong came to light only yesterday when it emerged that 146 students in the U.K. were given the wrong A level grade, resulting in 13 of them being denied a place at university. This was because of a failure in the examination board’s online marking system.
A mole of information
Posted on 20 February 2011 at 14:41h
How big is a mole? A group from the University of California has for the first time estimated the total amount of information stored digitally in the world. In a recent article published in Science Magazine they estimated that currently (well actually in the year 2007) 94% of the information in the world is stored in digital format. They concluded that people are storing almost 295 exabytes of information - that is almost 300 billion gigabytes or 3.0 x 1020 bytes of information.
It is not often you see numbers of this sort of magnitude bandied about – unless, of course, you are a chemist. Maybe in this era, where students are often more at ease with technology that their teachers, we have finally got a concept we can use to try impress upon our students exactly how massive the value of Avogadros’ Constant (L) really is.
We would only need another 1999 planets identical to Earth to store and communicate just one mole of bytes of information. Put another way that is 602 zetabytes or 0.602 yottabytes of information.
Thinking critically
Posted on 19 February 2011 at 11:24h
How can we get our students to think critically? Often there seems to be so little time just to cover what is on the IB Chemistry syllabus let alone get them to think and criticise what they read or are told. By the time they reach age 16 or 17 much of their innate curiosity seems to have been drummed out of them by the demands of taking one exam after another. I think we can no longer rely on students to think critically unaided. We need to show them how whenever the opportunity arises.
I’ll try to illustrate this with just one example. I’ve recently written the webpage on Nucleophilic addition to cover sub-topic 2 in Option G. Superficially it is very straightforward. Just one reaction really – the addition of hydrogen cyanide to aldehydes and ketones. All the text books, websites etc. make it look so simple.
The carbon atom of the C=O group is δ+ as oxygen is more electronegative than carbon. So cyanide ions, CN-, are attracted to it to form an intermediate anion with the negative charge on the oxygen. This anion then picks up H+ to form the cyanohydrin product. This sums up pretty much all there is about this in the text books. All students have to do is learn it, answer the questions by essentially repeating this in the Paper 3 examination and they are on their way to achieving grade 7. But is it really this simple?
Firstly consider the nucleophile. The topic actually says the nucleophilic addition of hydrogen cyanide not cyanide ions. Why can’t hydrogen cyanide itself act as the nucleophile?
Like water and ammonia, two nucleophiles that students have already come across when studying nucleophilic substitution, hydrogen cyanide is also a polar molecule with at least one non-bonding pair of electrons. A student might reasonably expect the non-bonding pair of electrons on the nitrogen atom to be attracted to the carbonyl carbon atom (similar to what happens with ammonia when it substitutes in halogenoalkanes). Clearly this doesn’t happen – why not?
Now consider the cyanide ion which does act as the nucleophile. It actually contains two non-bonding pairs of electrons. One on the carbon atom, and one on the nitrogen atom (see below). Nitrogen is more electronegative than carbon so it would seem reasonable that it would be the more negative nitrogen atom that would preferentially approach the carbonyl δ+ carbon atom to form a C-N bond but this does not happen. Why not?
You can extend this to look at how a cyanide ion can act as a ligand with transition metals. Again its Lewis base properties depend upon the non-bonding pair of electrons on the carbon atom not the more electronegative nitrogen atom. It is the carbon atom that forms the coordinate bond to the transition metal as in iron(III) hexacyanide, [Fe(CN)6]3+.
An analogous situation arises with carbon monoxide which is isoelectronic (contains the same number of electrons) to the cyanide ion. It too has two non-bonding pairs of electrons (see above). Why isn’t carbon monoxide a good nucleophile – the carbon atom and the oxygen atom both have one non-bonding pair of electrons they could use to approach a δ+ carbon atom? After all it is a good ligand and like cyanide ions when it acts as a Lewis base with transition metals again it is the non-bonding pair on the carbon atom, not the more electronegative oxygen atom, which forms the coordinate bond (as, for example, is shown in the image on the left for iron pentacarbonyl, Fe(CO)5).
I’ve asked a lot of questions here and given no answers. Shouldn’t we be training and encouraging students to ask these sorts of basic questions instead of just accepting what is on the syllabus without really understanding it?
Curriculum review
Posted on 16 February 2011 at 11:16h
.jpg "Report of the first Curriculum Review meeting which can be downloaded from the OCC")
The IB Chemistry programme (along with the other Group 4 subjects) is due to be revised to start teaching in September 2014 with the first examinations in 2016. In October last year 24 participants (including 16 IB teachers) held the first review meeting which looked at Group 4 subjects as a whole. The first subject specific meeting will be held early this year. The report of the October 2010 meeting has just been published and practicing IB teachers can download it from the Chemistry page on the Online Curriculum Centre (OCC).
Two major recommendations emerged from the meeting. The first concerned Higher Level and contains no real surprise. The new Higher Level courses must be up-to-date and be a good preparation for students to go on to further study at university as well as giving them an element of all round scientific literacy. The second recommendation addresses the fact that the meeting felt that there is no clear distinction between Higher Level and Standard Level courses. It is proposed to design a new Standard Level specific course called ‘Science and Technology’. This course would be for those students who may not study science again but will provide them with an understanding of scientific issues and how they impact upon their lives. This course may, or may not replace existing subject-specific Standard Level courses. For those of us with longer memories this has echoes of the concept behind the old (pre-1996) Standard Level Applied Chemistry which was very much a Chemistry course for those not going on to study science at university or beyond.
The meeting also looked at Internal Assessment where it was acknowledged that the present scheme is still problematical. Some time was spent discussing the fact that state of the art software has blurred the distinction between real and virtual investigations. Practical activities need to be widened to take on board new developments in technology and to reflect the real world of science. As I predicted in my blog on Practical work and assessment it seems likely that more of it could be assessed through written papers than is currently the case.
The meeting also looked at assessment and intends to reduce the Standard Level examinations to just two papers and also reduce the number of options offered to four. Surprisingly there is no mention of the assessment weighting except to say that Internal Assessment may be reduced from 24% to 20%. The IB is out of line with other major international examinations in the weightings it gives to the Objectives (see my earlier blog on Syllabus content). The IB gives 28% to the higher level of thinking Objective 3 whereas the Cambridge Pre-U, for example, allocates 40% of the total marks for this with less on factual recall. I hope in future meetings this will be discussed.
One other thing that surprises me is that there seems to be little discussion about how the sciences differ. Only since 1996 have the three sciences Physics, Chemistry and Biology followed the same IB model. Why should this be as they are very different subjects? They may all follow the scientific method but they do it in very different ways. The IB does recognise this fact with Design Technology, a Group 4 subject which is allowed to be different - why can't Chemistry also go its own way?
There are still more than three years before the new Chemistry syllabuses (syllabi?) come into being. If past experience is anything to go on the final versions will incorporate some but not all of these suggestions – watch this space.
A-Levels 'not fit for purpose'
Posted on 15 February 2011 at 11:37h
In a damming report published today the Royal Society has condemned British A-Levels as not being fit for purpose. Specifically in its State of the Nation report it bemoans the fact that many students are applying for university having studied only one science subject and no mathematics. It calls for what all IB teachers already know – a broader-based baccalaureate-type education!
The spice of life?
Posted on 11 February 2011 at 16:53h
Curcumin is one of the compounds covered in Option F: Food chemistry. It is found in turmeric – the yellow spice used in Indian curries. It is included in the IB Chemistry programme as it is an effective natural antioxidant. It may now have a use for victims of strokes.
tumeric powder and roots
The structure of a molecule of curcumin shows the presence of two phenolic groups which account for its antioxidant properties. You can also get your students to explain why it is coloured (due to the extensive conjugation of the double bonds). This could be used either in Option A: Modern analytical chemistry (A.8.4) or in Option F (F.10.2).
It was reported yesterday by Dr Paul Lapchack who works at the Cedars-Sinai Medical Center in Los Angeles that a new compound, CNB-001, has been developed from curcumin. This compound is more effective at crossing the blood-brain barrier than curcumin and has been shown to be effective in mice at repairing stroke damage. There are hopes that it may be able to regenerate brain cells if given within three hours of a patient suffering a stroke and trials are about to begin on humans. A video describing this has been produced by Insider medicine.
Real (as opposed to virtual) chemistry
Posted on 09 February 2011 at 17:47h
Today a blue plaque is being erected outside a house in Notting Hill, London to commemorate the life and work of Sir William Ramsey. This is part of the way in which the UK is celebrating the International Year of Chemistry. William Ramsey (1852-1916) was a Scottish chemist who won the Nobel Prize in 1904 for his discovery of the noble gases. The house in Notting Hill is where Ramsay lived while he was Professor of Inorganic Chemistry at University College London. What Ramsey did was to compare the molar mass of the ‘nitrogen’ obtained from air once the oxygen, carbon dioxide and water had been removed with the molar mass of nitrogen gas obtained by chemical means. The very slight difference led him to discover argon which then led him further to discover helium, neon, krypton and xenon - a whole group of the Periodic Table which was previously unknown.
I wonder if a modern chemist would have reached the same conclusion? The difference in mass and density was very small and could easily have been put down to ‘experimental error’ or attributed to the uncertainties inherent in the apparatus. Are we teaching our students the skills to physically perform experiments with such care and dexterity? I often debate with Chris Hamper (who runs the InThinking Physics website) about the validity of simulated experiments. If Ramsey had relied totally upon simulations for his experimental work then I very much doubt if he would have been successful. A simulation is only as good as the people that write the programme. How could someone who has absolutely no knowledge that a whole group of ‘inert’ elements exists incorporate the presence of argon into a simulation package. Don’t misunderstand me. I can see that simulations have many excellent points (virtual libraries and combinatorial chemistry to mention just two) but they should never be allowed to replace completely ‘real’ hands-on practical chemistry’.
Without Ramsay’s discoveries we would not have neon advertising. The first neon sign was demonstrated by George Claude at the Paris Motor show in 1910. The video “How neon tubes are made” produced for Bright Neon Signs is worth watching.
Multiple choice answers
Posted on 07 February 2011 at 11:21h
Although some multiple choice questions can be quite challenging generally the markscheme is clear and there is only one correct answer for each question. In fact as you can see (below) from the instructions given on the front of the question paper students are required to give the best answer rather than the correct answer as occasionally another answer apart from the best answer could be considered correct under certain specific circumstances.
But what happens if there is more than one ‘best’ answer? Teachers are encouraged to do the paper themselves after the students have sat the examination and comment on the G2 form about any particular problems they have come across. At the grade award meeting these comments are scrutinized and if the examiners agree they have the option to delete the question or allow two right answers. An example of this occurred in the M2001 Paper 1 SL examination. Question 11 asked which out of MgS, HCl, CO2 and CaO had the greatest ionic character. Initially the answer given was CaO as it has the largest difference in electronegativity values. However some teachers argued that the states were not given and HCl is a strong acid in aqueous solution so is fully dissociated into ions. At the grade award meeting it was decided to accept both HCl and CaO as correct answers. When this does happen the decision is referred to in the Chief Examiner’s Report published shortly after the examination session has ended.
Within the next few weeks teachers are likely to be giving a mock examination to their students and one of the likely contenders for the mock exam are the May 2010 TZ1 papers. Take a look at Question 22 on the SL Paper 1 (the same question appears as Question 26 on the corresponding Higher Level Paper). Essentially the question asks which is the correct statement about two solutions of equal volumes of NaOH(aq) and NH3(aq) when both solutions have a concentration of 1.0 mol dm-3. The answer according to the markscheme is answer C which states that sodium hydroxide has a higher pH than ammonia. This is clearly correct and the two answers A and B are obviously wrong. However answer D states “Sodium hydroxide has a higher hydroxide concentration than ammonia”. This answer is clearly correct too and is essentially a rewording of answer C since a higher hydroxide concentration will result in a higher pH value. I find it amazing that this seems to have got completely through the system without being challenged by teachers on the G2s and not being altered at the grade award meeting. There is no specific mention of this question to explain why only answer C is correct in the M2010 TZ1 Chief Examiner’s Report. If you do use this as your mock examination it will be interesting to see if any of your students comment upon it. Possibly a printing error has occurred in the papers or markscheme sold after the session had ended.1
Perhaps this illustrates that with the best will in the world mistakes can still get through – after all examiners (and the people who print the examination papers) are only human. I am acutely aware of this myself when I put material on this site. Because I cannot use past IB questions for copyright reasons all my 500 or so multiple choice questions are brand new. I have checked them and the answers as carefully as I can but they have not been externally checked so if you do find any errors please let me know. One of the great advantages of a live website is that mistakes (once pointed out) can be rectified immediately.
1. In fact I have just found out that it was a printing error in the CD that was sent out (so the examiners are off the hook!!). On the original paper the wording for answer D was "When the basic solutions exactly neutralize separate identical solutions of ethanoic acid, more of the ammonia solution is needed". This explains why there was no comment on this question in the Chief Examiner's Report.
Relevant environmental chemistry?
Posted on 02 February 2011 at 12:27h
The IB Diploma is clearly international but how far does it reach within society? In the early days almost all IB schools were private schools which just educated the elite. Now in many developed countries such as the US and the UK more and more state (public) schools have joined the IB so that in theory the course is open to any 16-19 year old. This is far from true in many other countries though where only those who have received an education in English (or Spanish or French) and who have sufficient financial means and social standing can follow the programme. I feel that the IB Chemistry syllabus and examinations do not always reflect this.
Some years ago there was a question on Paper 3 for the Environmental Chemistry option. The question basically asked how a householder could save water. What was interesting were the two suggested answers. 1. Take a shower rather than a bath and 2. Put a brick in the toilet cistern. Both of these answers showed how culturally ignorant the examiners were. Many households throughout the developing world do not have baths, shower or toilets or even taps and running water. Many people have to go to a well or pump or river to get their water. For these households the answers were a nonsense but, of course, generally these are not the homes where our IB students come from .
A similar issue arises with pollution. The Environmental option tends to be much more concerned with pollution caused by the rich people of the world who drive cars and have refrigerators etc. In fact the world’s most deadly pollution comes from smoke within peoples own homes. In many parts of the world families cook on wood or dried animal dung fires without proper ventilation. The fumes from these cause many respiratory and eye-related diseases.
It is estimated that over two million people die each year from the pollution caused by these fires with 44% of these being from childhood pneumonia – the biggest cause of child death in the world.
The Global Alliance for Clean Cookstoves supported by the UN has recognised this and has launched an initiative to try to reduce this death toll. Perhaps as well as focusing on catalytic converters and alternatives to CFCs the IB syllabus should also look at the pollution problems associated with the many people who probably will never get the chance to study for the IB Diploma.
Perhaps at least we can make our students more aware of the problems faced by many in their day to day living. This could also provide fertile ground for meaningful CAS projects.
Anyone for tennis?
Posted on 29 January 2011 at 12:03h
Chemistry has finally made it in the world of tennis -well two elements have almost done it.
Lithium and sodium (aka. Li Na) played in the final of the women’s Australian Open Championship today (29 January 2011).
Unfortunately for Chemistry Kim Clijsters prevailed and won the final 3-6, 6-3, 6-3. Hopefully Li Na from China has a bright future ahead of her and will one day become a Grand Slam champion.
Watch this space!
International Year of Chemistry
Posted on 26 January 2011 at 12:22h
2011 has been officially designated the International Year of Chemistry. You can download a prospectus 
which sets out the aims of the year which was jointly proposed by IUPAC and UNESCO and officially adopted by the UN.
Essentially the aims are to:
• Improve the understanding and appreciation of chemistry by the public.
• Enhance international cooperation by serving as a focal point or information source for activities by national chemical societies, educational institutions, industry, governmental and non-governmental organizations.
• Promote the role of chemistry in contributing to solutions to global challenges.
• Build capacity by engaging young people with scientific disciplines, especially the scientific method of analysis developed by hypothesis, experiment, analysis and conclusions.
Many different organisations in almost every country in the world are organising events to celebrate and publicise the year. For example, to name but two, the Royal Society of Chemistry and The American Chemistry Society.
In a small way this website is making a contribution. Since it was launched on 18 January, one week ago, IB Diploma Chemistry teachers from 82 different countries have logged in – IB Diploma Chemistry is definitely international!
What is your country doing and what will you be doing with your students to celebrate this special year?
Syllabus content
Posted on 24 January 2011 at 16:25h
I’ve recently written a proposal for a 16-19 Chemistry syllabus for a group of Egyptian schools to fit the brief that it should meet ‘International Standards’ as well as fit the Egyptian curriculum. This has meant looking in detail at other internationally recognised programmes such as the International A Level, the Pre-U Cambridge Examination, Advanced Placement (AP) and the European Baccalaureate (EB) as well as the International Baccalaureate. It has been an interesting exercise and one in which the IB comes out of rather well. Even so, we can learn from other programmes and consider what they include and what we leave out and vice versa.
The IB is quite distinct in having so many options. This has many advantages and indeed I was one of the teachers pressing for this when the syllabus was overhauled in 1996 so that the good points from Applied Chemistry could be incorporated when it was subsumed into Chemistry. There are some disadvantages though. It worries me that a Chemistry student can gain the IB Diploma without knowing anything about the principles and uses of spectroscopy and personally I think it was a mistake to remove the basics of this from the core during the last review in 2007. One other noticeable fact is that some of the other programmes place more emphasis on Objective 3 and less emphasis on recall than the IB. In the IB Objective 3 type questions are worth 28% of the final mark whereas for A level and the Cambridge Pre-U they are worth 30% and 40% respectively.
There are many topics that we used to include such as colligative properties that are still retained in some of the other programmes (e.g. AP) and we have topics, such as Combinatorial Chemistry, which as far as I am aware do not appear in any other 16-19 year old Chemistry syllabus. But what are the topics that other programmes cover which we have never included?
The Cambridge Pre-U Chemistry syllabus has some interesting new topics. These include van Arkel diagrams, C-13 NMR and anti-bonding orbitals. Another topic that occurs on some of the other programmes is the concept of ‘atom economy’ which fits in with the idea of ‘Green Chemistry’.
Van Arkel diagrams are used to help explain the bonding in all types of binary compounds. By plotting their position on a single graph using electronegativity values a van Arkel diagram aims to unify all chemical bonding types whether they are ionic, covalent, metallic or semi-metallic. It is a step-up from the rule of thumb (which does not work very well) that a compound is ionic if the difference in the electronegativity values of the two constituents is more than 1.8. However I personally do not find them much more convincing than just interpreting the electronegativity values within the context of the Periodic Table.
Carbon-13 NMR. I wonder if this is included as it is simpler to deal with than 1H NMR. The big advantage of C-13 over 1H NMR is that the chemical shifts are predictable and the spectra are routinely decoupled. The Pre-U claim that as a result questions can be considered that involve more complex and interesting molecules. However the real strength of 1H NMR is the splitting patterns caused by neighbouring protons. I feel that once students understand how to interpret splitting patterns and the integration trace then the chemical shift becomes less necessary as a tool to elucidate structures. From an intellectual point of view I favour 1H NMR over C-13 but of course the best outcome would be to have both on the syllabus!
Anti-bonding orbitals. I always feel uncomfortable that the IB includes molecular orbitals and hybridisation but does not include anti-bonding orbitals when looking at the combination of atomic orbitals to form molecular orbitals. For this reason I have included a brief mention of them in my IB Chemistry Course Companion. The Pre-U includes them for their importance in spectroscopy. How else can one explain the transitions that occur when considering whether an organic molecule will absorb in the UV or visible region? Currently in the IB we just mention degree of conjugation (or delocalisation) but an understanding of electronic transitions to anti-bonding orbitals would be helpful here.
Atom economy. This term was coined by Barry Trost of Stanford University US (for which he received the Presidential Green Chemistry Challenge Award in 1998).
Atom economy = Mass of atoms in desired product x100
Mass of atoms in reactants
This is different to, and more useful than, the percentage yield. The percentage yield gives some useful information but does not show how efficiently the reactants have been used in industrial processes or how effectively the amount of waste products is being reduced. The real strength of using the concept of atom economy is in comparing different routes or pathways to synthesise the same product.
When the IB Chemistry programme next comes up for review it would be worth the reviewers considering what changes would bring the IB more up-to-date. There is not room to include everything in the programme so by necessity a judgement has to be made and some valid topics omitted. However, some of these topics omitted from the programme can still be included in the examination as they provide fertile material for the Data Response questions in Section A of Paper 2. Here much of the necessary background information can be provided to the students in the questions. You can also use these omitted topics in your teaching to stretch your students and challenge and prepare them to apply their knowledge to solve problems in unfamiliar areas.
Atomic masses change
Posted on 30 December 2010 at 18:22h
It has been known for a long time that the relative atomic mass, Ar, of lead, Pb, changes slightly depending upon the origin of the lead as it is the end product of natural radioactive decay series. If the lead originates from an area rich in 238-U then the end product will be richer in 206-Pb whereas if the area was originally rich in 232-Th then the resulting lead will have a slightly higher relative atomic mass as the end product of the decay of 232-Th is 208-Pb. However, the working assumption has always been that the relative atomic masses of the other elements are fixed and precise values are given in all Periodic Tables. This has now changed. Now the only fixed values are for those elements with only one stable isotope such as fluorine, aluminum, sodium and gold.
In a recent publication by Michael E. Wieser and Tyler B. Coplen (who work at the University of Calgary,Canada and the U.S. Geological Survey, Reston, USA respectively), the values for the relative atomic masses of eleven common elements have been revised. These are hydrogen, lithium, boron, carbon, nitrogen, oxygen, silicon, sulfur, chlorine, germanium and thallium. For germanium the change is straightforward – from 72.63 to 72.64. The change is anything but straightforward for the other ten elements. Instead of a single value the relative atomic masses for these ten elements are now given as a range depending upon the precise isotopic make up of the particular source of the sample i.e. its physical, chemical and nuclear history. This will not affect IB chemistry calculations to any great degree as the range is quite small and in fact to two decimal places it often has the same value as that given in the IB Periodic Table (Table 5 of the IB Data Booklet). For example, the range for hydrogen is 1.007 84 to 1.008 11. The old value was 1.007 95 which is actually unchanged at 1.01 when quoted to two decimal places. For some of the other elements the change is just significant to register at two decimal places. Thus boron now will be quoted in the range 10.806 to10.821. So the relative atomic mass to two decimal places could be 10.81 or 10.82 (the old value was 10.811 which corresponds to the value of 10.81 given to two decimal places in the current IB Chemistry Data Booklet).
In a news report about the published article the International Union of Pure and Applied Chemistry, IUPAC, explains that advances in modern analytical techniques (Option A) means that relative atomic masses can now be measured much more precisely. These small changes, due to the relative abundances of particular stable isotopes in the sample, are important in research and industry. For the IB they can also be related to particular options. For example precise measurements of isotopic carbon abundance and be used to determine purity in food products (Option F) and precise measurements of the nitrogen content can be used for tracing pollutants in streams or underground water systems (Option E). There are uses for Option B: Human biochemistry too. Performance enhancing steroids can be detected in the human body because the relative atomic mass of carbon in natural testosterone is higher than in testosterone from pharmaceutical sources.
This is an interesting TOK aspect to Chemistry in that it shows how scientific ‘knowledge’ is constantly changing and indeed that the Law of Constant Composition is not as immutable as it was once thought to be (see the page on Topic 1 under Incorporating 'Aim 8', TOK and the International Dimension in Core and AHL). One other noteworthy aside is that if you look at the articles nowhere is relative atomic mass mentioned. IUAPC still calls it relative atomic weight!
Practical work and assessment
Posted on 27 December 2010 at 14:40h
Probably the most contentious area in the current IB programme is the assessment of practical work. Teachers who have recently retired or moved away from teaching the IB have told me that they only thing they don’t miss is the IA. This dissatisfaction with the whole of the IA is also obvious at workshops where it can tend to dominate the discussions and it can also be clearly seen by the number of times it crops up in one form or another on the OCC discussion forum. The IB practical programme does have one very real strength. Teachers are completely free to devise their own programme and the assessment part of it only needs to take up about 15 hours (plus the ten hours for the Group 4 Project) so much of the programme can be tailored to suit the needs of students. Unfortunately the somewhat haphazardous nature of the assessment has taken much of the enjoyment out of practical work. Many teachers now spend most of the time (40 or 60 hours) doing assessed practicals which means that good practicals which do not meet the assessment criteria tend to get passed by. It is to be hoped that the current review of the programme will produce significant changes for the new programme for first examinations in 2016.
So what can be done to improve it? My feeling is that the current programme is neither scientifically or educationally sound. It seems odd that students MUST perform five different types of ICT but do not have to learn and use fundamental chemistry manipulative skills, for example, reflux (see image on the right). Are our students actually good practical chemists by the end of the course? – at the moment there is no guarantee of this. It also stereotypes the scientific method with absolutely no credit given for using imagination (or, in IB Learner Profile parlance, ‘taking a risk’.) The whole process of designing an experiment is also flawed. Chemists usually do know what the problem is (rather than just ‘investigating some aspect’) – the challenge is how to solve the problem. On top of all this with the best will in the world there is no certain format to moderate samples from all schools in a reliable and unbiased way. So how could it be changed to accommodate these points and still retain its strength?
1. Change the way of assessment. Some factors like recording raw data, working safely with respect for others and working in a team can only be assessed fairly by the teacher (or by self- or peer assessment) during the two year course. Other factors, like processing and presenting data, drawing a conclusion and evaluating an experiment can be assessed just as well using a written examination paper. I would suggest reducing the internal summatively assessed mark to no more than 10% of the total amount and the remaining 10-14% for practical work can be examined externally through a 1 hour written paper. By reducing the percentage of the internally assessed component many of the current problems (perceived or actual) due to moderation would be significantly reduced. This could be aided by linking the moderation (as it used to be before 1998) to the quality of the programme and how the school as a whole performs on the written practical paper.
2. Stipulate the manipulative skills that must be performed by the student during the two year course and that the teacher must show (on the form 4PSOW or equivalent) which experiment(s) was used to exemplify each skill. These skills could be:
Carry out each of the following with due regard to accuracy and safety.
- Precise transfer/measurement of volumes of liquid using a pipette and burette
- Measurement of mass by difference using a top-pan balance
- Measurement of temperature by the correct use of a thermometer
- Measurement of gaseous volume
- Separation of a solid-liquid mixture by filtration
- Separation of two immiscible liquids using a separating funnel
- Separation of a mixture of two or more components by paper or thin layer chromatography
- Determination of the melting point of a pure organic compound
- Distillation
- Reflux
- Recrystallisation
- Use of a data logger to record raw data
- Use of software for graph plotting
- Use of a spreadsheet for processing data
- Use of a data base
- Use of computer modelling or simulations
3. Encourage students to extend their practical abilities by giving credit for imaginative and original solutions to design experiments rather than just following well-worn and predictable paths.
Hopefully this will provide some food for thought for discussion particularly to those reviewing the programme.
World's smallest Periodic Table?
Posted on 22 December 2010 at 15:40h
Two days to go to Christmas. What do you give a chemist for Christmas? Well, although it was for his birthday, not Christmas, Nottingham University’s Dr Mike Fay at the Nanotechnology and Nanoscience Centre has presented Professor Martyn Poliakoff with his very own Periodic Table. What is unique about this present is that it is written on one of his own hairs. Martyn Poliakoff is the author of the excellent series of videos on the Periodic Table – a fantastic resource for teaching Topics 3 and 13. This particular Periodic Table was etched on one of his (silver!) hairs using nanotechnology to produce a table with the dimensions of just 89.76 μm across and 46.39 μm from top to bottom (helium to lawrencium). Each element is just 4 μm across so takes up an area of just 16 μm2 (16 x 10-12 m2). As Professor Poliakoff says, “It is the best birthday present I have had today -although I've only actually had two presents”. It can probably claim to be the world’s smallest Periodic Table. The video clip
below shows exactly how it was done and is well worth showing to your students.
Blue light cystoscopy
Posted on 10 December 2010 at 15:07h
Recent research into cancer detection and treatment provides an interesting example of how connections can be made between various parts of the IB syllabus. Specifically porphyrins in hemoglobin (B.9.2), UV-VIS spectroscopy (A.8.4), enzymes (B.7.1), drug design (D.8.4), functional groups (10.9.1), esterification (20.4.1) and acid-bases (8.3.2) – to name just a few!
Protoporphyrin IX (PpIX) (left) is a porphyrin derivative that combines with Fe2+ ions to form the heme of hemoglobin, i.e. it is an intermediate in the biosynthesis of heme. It fluoresces in the red region of the spectrum with λmax of 621 nm. Mutant cancer cells, which proliferate excessively, accumulate substantially more PpIX than normal cells.
Part of the biosynthesis of PpIX involves the formation of 5-aminolevenulic acid which is catalysed by the enzyme 5-aminolevulinic acid synthase. If extraneous 5-aminolevulinic acid is added to cancerous cells it induces the biosynthesis of an excess of Pp IX. Shining blue light onto the cells photoactivates the PpIX which then fluoresces with its characteristic red light. Hence cancer cells show up in the blue light which aids in their early detection.
The effect of the aminolevulinic acid (right) is enhanced even further if it is delivered in the form of an ester (with a relatively long carbon chain) as this makes it more lipophilic which means it remains in the cancer cells longer. The ester (hexyl aminolevulinate) is delivered in the form of its hydrochloride salt, shown below, (causing protonation of the –NH2 group) to increase its solubility in water before the ion reverts back to its molecular form once inside the cell.
In the video below consultant urological surgeon Rhidian Hurle working at the Princess of Wales Hospital in Bridgend, Wales, UK shows how he is using this technique for the early detection of bladder cancer.
Explosives
Posted on 01 November 2010 at 11:13h
What might be flying with you – or even with your IB exam scripts, extended essays or IA samples for moderation as they are sent round the world as cargo courtesy of DHL? On 29 October 2010 two parcels that contained explosives were detected in cargo planes bound for the USA – one in Dubai and one in East Midlands Airport in the UK. The parcels are thought to have originated from Yemen.
The explosives (which in one of the parcels were concealed inside a printer ink cartridge) contained the explosive PETN. Explosives are not on the IB course as such although we do mention the role Fritz Haber played in fixing nitrogen which very probably prolonged the First World War. Most people have heard of nitroglycerine or nitrocellulose – but what exactly is PETN? In fact it is not new and was used as an explosive in World War I. It was first synthesised in 1891 by the German chemist Bernhard Tollens (1841 – 1918). Many will recognise the name Tollens as it is the same Tollens who introduced Tollens’ reagent, the silver mirror test for the presence of aldehydes using ammoniacal silver nitrate which also produces an explosive solid. Tollens and his co-worker Wigand nitrated pentaerythritol, C(CH2OH)4, to form pentaerythritol tetranitrate or PETN. It obviously has many similarities with nitroglycerine except of course it contains an extra nitro-group as the starting material possesses four –OH groups rather than the three in propane-1,2-3-triol (glycerol).
.png "pentaerythritol tetranitrate (PETN)")
I wouldn’t recommend discussing the synthesis of this with your students – MI5 (or is it MI6?) are probably logging this already(!) - but since many of us and our students travel internationally it seems reasonable to have some chemical knowledge of what we might be up against. PETN has been the explosive of choice recently. On Christmas Day 2009 a Nigerian student tried to blow up a NorthWest Airlines flight as it approached Detroit – the PETN was contained in his underwear - and a few years earlier in 2001 the ‘shoe bomber’ Richard Reid, had PETN concealed in his shoes and was prevented in his attempt to blow up an American Airlines flight en route from Paris to Miami. There are several reasons why terrorists are using PETN. Although not impossible, it is very difficult to detect and it is also considerably more stable than many other nitro- explosives such as nitroglycerine. I have seen one report that the recent bombs contained lead azide, Pb(N3)2 to initiate the reaction but it can also be detonated by an electric spark and a mobile phone was reported to be present with the bomb at East Midlands Airport. The ‘shoe bomber’ attempted to use triacetone triperoxide as his detonator. For this reason there are severe restrictions on the amount of liquids that most air travellers are allowed to take on board with them.
Like many substances, nitro- compounds can often be used for both good and bad purposes. Both nitroglycerine1 and PETN are used in medicine as vasodilators in heart conditions – so maybe there should be a small amount of these 'explosives' kept in the medicine cabinet on all planes!
Happy (and safe) flying!
1.There is a nice TOK point here related to language. In the same way that nuclear magnetic resonance is called magnetic resonance imaging in hospitals to avoid the use of the word nuclear, nitroglycerine is called glyceryl trinitrate to avoid the connotation with explosives.
Sticky tape & a pencil
Posted on 06 October 2010 at 14:37h
So you need fancy electronic data loggers or university analytical machines to do real research these days? Not so – all you need is a pencil and a roll of sellotape® (sticky tape). The Nobel Prize has just been awarded to two scientists working at Manchester University in the U.K. (the very place where I was awarded my Ph.D.!). Professor Andre Geim ( 1958 - ) and Dr. Konstantin Novoselov (1974 - ) who were both born in Russia were awarded the 2010 Nobel Prize for Physics for their discovery of graphene. Every IB student will recognise graphene as it is literally one layer of the normal structure of graphite where the carbon atoms are sp2 hybridized and arranged in hexagonal rings in a flat plane (see Assessment Statement 4.2.9). The difference is that graphite consists of many of these layers with delocalised electrons from the unhybridized p orbitals able to travel between them which explains why graphite is a good conductor of electricity. Typically a 1 mm layer of graphite contains about 3 x 106 individual layers of graphene stacked on top of each other.
What Geim and Novoselov were able to do was obtain single layers of graphene which are literally one atom thick and therefore virtually transparent and 2-dimensional. They first published their work in 2004. What is amazing is that they were able to obtain their single layers of graphene by using a roll of sticky tape to pull the layers off the ‘lead’ in a graphite pencil. Graphene has been shown to be extremely strong and a good electrical conductor which means it could have a wide range of practical uses. It is in fact about one hundred times stronger than steel and a better electrical conductor than copper. It is thought that it can replace silicon in transistors and find uses in touch screens and solar cells for example. This fits in neatly with the sections on nanotechnology and silicon and photovoltaic cells in Option C : Chemistry in industry and technology.
Nottingham University have already produced a video on graphene
There are several slightly bizarre facts associated with this award. Aged only 36, Dr Novoselov is one of the youngest recipients of a Nobel Prize in recent years. Ten years ago Professor Geim together with Professor Sir Michael Berry from Bristol University were jointly awarded a ‘tongue in cheek’ Ig Nobel Prize. These are given for ‘improbable research’ and they were awarded it for their experiments on levitating frogs using magnetic fields. Finally Professor Geim should perhaps be also awarded the Nobel Prize for modesty. When he learned that he had won the Nobel Prize he stated in an interview with the BBC that,
“In my opinion, there are several categories of Nobel prize winners. There are those who, after getting the Nobel Prize, stop doing anything for the rest of their lives, which is a big disservice for their community.
There is another type of person who thinks that other people think they won the Nobel Prize by accident. So they start working even harder than before."
I am in neither of these categories and will "muddle on as before".
Perhaps the only really bizarre fact is that despite discovering a material that is clearly a ‘chemical’ they were awarded the 2010 Nobel Prize for Physics not Chemistry – but then, of course, Physics is a minor branch of Chemistry.
How 'International' is IB Chemistry?
Posted on 09 September 2010 at 22:01h
Is IB Chemistry truly international? When I worked just in the British system teaching A level Chemistry I did not realise at the time how anglocentric my view of Chemistry was. I only used British (as opposed to US, Canadian or Australian etc.) books. ‘Dot and cross’ diagrams were the norm for drawing what I now call Lewis structures as was expanding the octet for molecules such as sulphur dioxide and sulphur trioxide (note the ph spelling of sulfur too!). I also learned names such as Dalton, Davy, Priestley and Faraday as the pioneers of Chemistry. Working with international students and setting examinations for both the International Baccalaureate and the European Baccalaureate has widened my horizons considerably and made me realise that Chemistry is perceived differently in different countries. Recently, though, I have realised that both the IB and the EB are not really ‘International Chemistry’. They are in fact ‘western Chemistry’.
Kazakhstan is now an independent country but it used to be part of the USSR. The president of Kazakhstan, Nursultan Nazarbayev, has given his backing to setting up twenty specialist schools called the JSC “Nazarbayev Intellectual Schools”. These schools will specialise in the sciences and maths and will be trilingual (Kazakh, Russian and English). The proposed Chemistry syllabus has been drawn up by some very eminent Kazakh chemists and is very impressive. I have been asked to visit Kazakhstan in order to review the programme and make constructive suggestions to bring it into line with international standards so that it will be accepted as a university entrance qualification worldwide. I have found it fascinating to look at a programme which has been put together by chemists who essentially learned their chemistry dominated by USSR culture. Of course much of the actual chemistry is the same, but its cultural context is different. Let me give just one example. In the West we know of Mendeleyev and Markovnikov but generally Russian chemists do not readily spring to mind. Throughout the Kazakh syllabus there are references to A.M. Butlerov. I must confess that I have never heard of Butlerov so I thought I would look him up. It seems that he is little known in the West. Wikipedia only has a very small entry and the ‘latest’ article in a western journal about Butlerov is dated 1940. In 1978 (the 150th anniversary of his birth) a tribute was published in the Russian Chemical Bulletin. There is also a translated article available from the Russia-Infocentre.
Alexander Mikhaĭlovich Butlerov (1828-1886) was born in the town of of Chistopol near Kazan which lies at the confluence of the Volga and Kazanka Rivers in Russia. He became a professor of Chemistry at Kazan University and later (on the recommendation of Mendeleyev) at St Petersburg University where Markovnikov was one of his students. For some reason the name of Butlerov seems to have been ‘airbrushed’ out of western chemical culture and yet his achievements are of immense importance. Butlerov was the first person to realise that structural formulas should not just be an abstract image of a molecule but they should represent the true structure and that each organic compound is made of molecules that have their own specific structure. He reasoned that studying the chemical properties of substances can lead to their chemical structure and vice versa. This is something we now take for granted and yet it is crucial for the understanding of organic chemistry. Using this logic he was able to predict the existence of many new organic compounds. For example, he was able to synthesise isomers of butanol and pentanoic acid1 (known then as ‘valeric acid’) which were predicted by his theory. Perhaps we should be asking why we in the West remember Kekulé for determining just one structure – the structure of benzene- but ignore Butlerov who arguably made a much greater contribution to organic chemistry. In Kazakhstan and Russia he is known as ‘The creator of the theory of chemical structure’.
1As an exercise for your students you might like to ask them how many isomers of pentanoic acid (which must contain the –COOH group) they can find. The article in Russia-Infocentre states there are four but I can find five – four structural isomers but one of them has a chiral carbon atom.
Women in Chemistry
Posted on 26 August 2010 at 17:09h
Two thirds of people living in the UK cannot name a single female scientist either living or historical. For 18-24 year olds this figure rises to 88%. These shocking figures from a recent survey by the Royal Society are also depressing as they reveal that only 50% of the population could name any scientist, male or female. Most who could, named Einstein. The figures are only for Britain but I wonder if they are true for other countries too?
Assuming this is a worldwide phenomenon (as opposed to a uniquely British problem) it raises many important issues. One of the concerns I have about our current IB Chemistry syllabus is that apart from the discovery of penicillin (assuming you do Option D) it contains no historical references and in a sense it is devoid of the culture of Chemistry. How can we expect our students to know of famous scientists if we do not refer to them in our teaching? There will soon be a new generation of Chemistry teachers who, unless they have done their own research, will be seriously lacking in any knowledge of the background of our subject.
The lack of knowledge of famous female chemists is a slightly different problem. Unlike their male counterparts there simply are not very many. When I was drawing up my Chemistry quotations that appear on the side of each page I was struck by difficult it is to find any by women. Off hand, how many famous female chemists can you think of? The Royal Society has produced a list of ten famous British female scientists. Only four of them were involved in Chemistry. Three of these made their name in crystallography: Kathleen Lonsdale (1903-1971) crystal structures of inorganic and organic molecules, Dorothy Hodgkin (1910-1994) structure of penicillin and vitamin B12 and Rosalind Franklin (1920-1958) structure of DNA. The fourth was Elsie Widdowson (1908-2000) a nutritional chemist. Perhaps the most famous female chemist worldwide is Marie Curie (1867-1934) who won two Nobel Prizes (one for Physics and one for Chemistry) for her pioneering work on radioactivity. The only other famous female chemist that springs readily to my mind without doing any further research is the Canadian Maud Menten (1879-1960) who worked on enzyme kinetics. It is perhaps not surprising that there are very few famous women scientists from more than 100 years ago as many of the universities and scientific professions and societies were closed to women. However for many decades now women have had more or less equal rights to education and to the professions in most parts of the world. When I look back at the numbers of students I have taught IB Chemistry to over the past thirty years I estimate that slightly more than half were female and this ratio is also true for the teacher participants who have attended the many Chemistry IB workshops I have run. Women are certainly studying and teaching Chemistry but somehow they are either not making as much impact as men or their achievements are going unrecognised. There is certainly some truth in this last statement as many people have re-evaluated the work of Rosalind Franklin and feel that she deserved the Nobel Prize in 1962 for elucidating the structure of DNA just as much as Watson, Crick and Wilkins. I think that all teachers of IB Chemistry need to be aware of this problem. There is a lack of role models from the past – somehow it needs to be changed for the future.
Agricultural chemistry - an option?
Posted on 22 August 2010 at 13:05h
In the early 1970s when I first started teaching the 16-19 age range I worked at a comprehensive school in Whitby in Northern England and lived in a small fishing village called Staithes in Yorkshire. Staithes is where the British explorer Captain Cook worked as an apprentice to a grocer and where he is thought to have gained his love of the sea. Although a few of the people living in the village still earned their livelihood by fishing, most worked in the newly opened potash mine at Boulby a few miles north along the cliff top.
Potash used to refer to potassium carbonate, K2CO3, but now it refers to any minerals containing potassium and the Boulby potash mine produces mainly potassium chloride. The potassium was deposited millions of years ago by inland seas and the mine is very deep (1,200 – 1,500 m). In fact so deep that scientists from the Institute of Underground Sciences are using it to carry out research into ‘dark matter’ (the ‘missing’ mass of the universe). The main use of the potash obtained from the mine is as fertiliser.
Because of this background I was interested to read recently that BHP Bilton, one of the largest mining companies in the world has launched a US$40bn hostile bid to take over the Potash Corp of Canada. This would give them control of much of the world’s output of potash. The question is why? What will they gain from it?
World food prices have been increasing recently and it has been calculated that global food production will have to rise by 70% by the year 2050 to meet demand. Investing in commodities like wheat (it takes 8 kg of grain to produce just one kilogram of beef) is fickle due to drought or floods some years with times of plenty in other years. What BHP Bilton have realised is that there will be an inexorable increasing demand for fertilisers in the coming years. Farmers will not be able to increase the amount of arable land to meet the demand so they will need to resort to technology and use substantially more amounts of fertiliser to increase their yields. The company that controls the potash will be the company that makes the money.
Apart from the fact that there will be increasing demands for more genetically modified (GM) food to meet the demand (F.5.2) much of the above does not really impinge on the current IB programme. In the old IB Applied Chemistry course there was an option on ‘Agricultural Chemistry’ – maybe there is a need to bring this back. Food production includes pesticides, insecticides, plant growth regulators (synthetic plant hormones) etc. as well as fertilisers and in fact may well contain more solid chemistry in it than the current Option F on food. Something to think about?
Objective 3?
Posted on 10 August 2010 at 20:34h
Consider the following typical IB question for HL Option C: Chemistry in industry and technology.
“Discuss the properties needed for a substance to be used in liquid-crystal displays.”
Discuss is an Objective 3 command term. The definition of discuss is, ‘Give an account including, where possible, a range of arguments for and against the relative importance of various factors, or comparisons of alternative hypotheses.’
This would seem to be very much an Objective 3 type question. The sort of factors a student might wish to include in such a discussion would be:
The chemical stability of the substance
The ability to maintain a liquid-crystal phase stable over a range of temperatures
The necessary polarity in order to change orientation when an electric field is applied
The necessity for a rapid switching speed
A student who included these four factors in their answer is likely to score very highly and they have indeed had to draw upon their knowledge of Chemistry to construct a suitable argument. There is just one problem. In reality this is an Objective 1 question because all they have had to do is recall what is written in the syllabus. If you look at C.6.5 you will see that both the question and the four properties are all listed. One of the problems of using command terms and giving very detailed notes in the syllabus is that students often are not required to think and select relevant factors for themselves they just need to repeat what is on the syllabus. This is one of the reasons why many teachers and students spend so much time practising with past papers. I once analysed the 25 mark Option D section of a HL Paper 3. Although superficially it had twelve Objective 3 marks according to the command terms used in reality 24 of the marks were objective 1 or 2. Strangely the only truly Objective 3 mark out of the 25 was for identifying a chiral carbon atom on a molecule they had not seen before. The command term used for this question was ‘State’ which is Objective 1!
A few years ago when I was writing the IB Paper 2 I included a question which did not have a ‘right’ answer. The markscheme basically said that if the student says ‘yes’ and gives a valid reason then give them the marks and if the students says ‘no’ and gives a valid reason then also give them the marks. The external advisor’s comment was that you cannot have a question which does not have a right answer in a Chemistry exam! The question was cancelled. But why do all Chemistry questions have to have ‘right’ answers? Other subjects such as History do not always have right answers. The Objective 3 skill is to construct an argument and give the strengths and weaknesses of opposing views. To see how my students would respond I gave them an end of year exam which had some typical IB-type questions then one final genuine Objective 3 question. The question was, “Which is more reactive, a sodium atom or a sodium ion? Explain your answer.”
You might like to think how you would answer this question – which does not start with a command term (but does have one in the second sentence).
The initial response from most students was that sodium atoms are more reactive as they readily lose an electron to form a sodium ion. Sodium ions have a noble gas configuration so are expected to be very unreactive. The experimental evidence is that if you put sodium metal on water then a vigorous exothermic reaction takes place and hydrogen, hydroxide ions and sodium ions are formed (with a suitable equation) whereas if you put salt (sodium chloride) in water it merely dissolves and the process is slightly endothermic. Put more succinctly, you put sodium chloride on your fish and chips you do not put sodium metal and chlorine gas separately on them!
However the student who thinks critically will go much further than this. What sort of sodium ion is being referred to in the question? Salt is not a sodium ion it is an ionic compound of sodium ions and chloride ions. If the question refers to sodium ions combined in a compound then the atoms are more reactive but what if we look at free sodium ions in the gaseous state? In fact, when you remove an electron from a sodium atom the process is highly endothermic. You need to put energy in to turn it into the gaseous state then you need to put more energy in to ionize it to form the sodium ion. The reason why the reaction of sodium metal with water is so exothermic is because of the large amount of energy released when gaseous sodium ions become hydrated by the water to form Na+(aq). If they feel uncomfortable using hydration energies (which are not strictly on the syllabus) then a similar argument can be made using the formation of sodium chloride from its elements and involving the lattice enthalpy. By drawing on their knowledge of Born-Haber cycles a good student can deduce this for themselves. I wish IB exams gave more scope for students to really show what they understand rather than more often asking them to simply repeat back what is on the syllabus.
Isotopes in teeth
Posted on 24 June 2010 at 20:46h
.jpg "Analysis of the strontium isotopes in teeth have shown that the remains buried in Magdeburg Cathedral, Germany do indeed belong to Queen Eadgyth, (c910-946).")
It seems strange to me that in Topic 2.1.7 you will need to discuss the use of radioisotopes and yet the theory of radioactivity as such is not on the syllabus. The examples listed in the teacher’s notes in the guide on page 51 include carbon dating which, of course, is perhaps the best known of all the classic examples. Carbon dating relies upon the fact that carbon dioxide in the air contains some 14C. Living things are continually replenishing their carbon content through respiration so they contain a fixed ratio of 14C to 12C. Once death occurs the 14C gradually breaks down and forms nitrogen by β- emission:
Because the half-life of carbon-14 is 5730 years the ratio of 14C to 12C gradually decreases and from its measured value the time that has elapsed since death can be determined accurately up to a period of about 60000 years.
The age of rocks which are of course much older can be determined by other radioisotope dating. For example 87Rb decays to 87Sr with a half-life of 4.88 x 1010 years (49 billion years).
So that different minerals containing strontium will have a different ratio of 87Sr to 86Sr depending on their age.
During the past twenty years archaeologists have used the analysis of isotopes of strontium in teeth to look at migratory patterns of humans as the ratio of the isotopes vary according to temperature, altitude, distance from the sea and local geology. This is a nice contemporary example to illustrate topic 2.1.7. Strontium, a Group 2 element, is absorbed by the body through soils and through the food chain where it substitutes for calcium. Depending on its source the ratio of 87Sr to 86Sr varies. As the strontium is absorbed by the body it becomes fixed in tooth enamel as the person grows thus providing a permanent record of the environment that the person grew up in.
This ‘geographical signature’ has recently been used to prove beyond reasonable doubt that bones found in Magdeburg Cathedral in Germany belonged to the Anglo-Saxon Princess Eadgyth. Eadgyth was the granddaughter of Alfred the Great and is known to have to have married Otto the son of Henry, King of Saxony which was part of the German empire in 929 AD. When Henry died in 936 AD Otto became king of Germany and Eadgyth ruled as his queen until she died in 946 AD. Analysis of the 87Sr to 86Sr ratio of the teeth found in her tomb in Magdeburg confirmed that she had indeed spent the early part of her childhood in southern England.
Chemistry & politics
Posted on 19 June 2010 at 20:11h
The chemical industry is big business and inevitably involves national and local politics. As teachers we are concerned not to bring our own political views into the classroom but this can mean that we become completely apolitical about our subject for fear of being accused of indoctrination. We should not be afraid of raising issues and asking pertinent questions in order to encourage students to develop their own views and opinions from an informed basis. Although there are no specific issues highlighted on the syllabus, many political issues arise under ‘Aim 8’ which covers social, environmental and moral concerns of chemistry.
Two recent news items raise very important questions about the morals of the chemical industry and society in general.
It used to be said that the commercial prosperity of a country could be judged by the amount of sulfuric acid it consumes (Justus Von Liebig, 1803-1873). Whilst this may still be true it cannot be extended to the amount of sulfuric acid it produces as many heavy industries have been transferred from the rich western developed world to less developed countries where both the rules and cost of regulation are much reduced. In June 2010 eight former local employees of the Union Carbide company in India were found guilty of causing death by negligence when toxic gas1 inadvertently released from the Union Carbide India Limited pesticide factory in Bhopal killed thousands of people. This was more than 25 years after the actual Bhopal disaster which occurred on the night of 2/3 December 1984. Seven of those found guilty were fined US$2000 each and given a prison sentence of two years (the eighth had already died). It is alleged that the Chief Executive of the American owned Union Carbide, Warren Anderson, knew about a safety report issued in 1982 which identified 30 hazards in the Bhopal plant and in a similar plant in the US. These hazards were dealt with in the US plant but ignored in Bhopal. Precise details of the damage caused in Bhopal are difficult to quantify as estimates vary. The official immediate death toll has been put at 2259 but many more have died since and some estimates put the total at more than 20000 with more than 500000 seriously affected.
Union carbide (which was taken over by Dow Chemicals in 2001) agreed to pay a sum of US$490 in full and final settlement in 1991 and no-one from the parent company has faced charges over the incident. Charges of manslaughter have been brought against Warren Anderson, the CEO, but he has evaded an international arrest warrant even though India has an extradition agreement with the USA. Union carbide maintains that the release was caused by an act of sabotage but this has never been proven.
The plant itself has still not been removed or decontaminated and more than 300 tonnes of toxic waste still continue to pollute the area heavily.
Contrast this with what has recently happened in the Gulf of Mexico. On 20 April 2010 the Deepwater Horizon, an oil rig owned by Transocean and leased to BP, exploded killing eleven workers. The subsequent oil leak resisted attempts to stem it for at least eight weeks during which time millions of gallons of crude oil leaked into the sea off the coast of Louisiana. BP initially downplayed the incident and estimated about 5000 barrels of oil a day were leaking – more recent estimates put the figure at between 35000 and 60000 barrels a day. Barack Obama, the US President, was very quick to lay the blame on BP and has made them accountable for the full cost of the environmental clean-up. Tony Hayward, the Chief Executive of BP has accepted responsibility and on 16 June 2010 (less than two months after the explosion) BP agreed a US$20billion settlement for victims of the disaster.
Why is compensation and blame for an industrial accident reached so quickly when it happens in a rich nation like the USA and yet more than 25 years on an industrial disaster in India that has had a much more serious effect on the lives of so many more people is still not resolved?
1 Even now the Union Carbide Company of India has not released the composition of the toxic gas. The leak was caused by water entering a holding tank of methyl isocyanate, CH3-N=C=O. Apart from methyl isocyanate which is extremely poisonous, other poisonous gases that may have been in the cloud of gas include phosgene, hydrogen cyanide, oxides of nitrogen, hydrogen chloride and carbon monoxide.
Fish oil
Posted on 07 June 2010 at 20:31h
A team of researchers led by Dr Robert McNamara at the University of Cincinnati, USA, has recently reported in the American Journal of Clinical Nutrition that boys aged 8-10 who take daily dosages of docosahexaenoic acid showed a big improvement in their ability to concentrate and in their performance doing tasks that involved attention.
This report is interesting for several reasons. It can be used to support Assignment statement B.4.4 on the Human Biochemistry option and Section F.2 on the Food Chemistry option. It is also interesting to look critically at the findings and the validity of claims involving food supplements.
The structure of docosahexaenoic acid
Docosahexaenoic acid, known as DHA, is an essential fatty acid that is found in fish oil. It has the molecular formula C22H32O2 and the IUPAC name docosa–4,7,10,13,16,19–-hexa–enoic acid with all the double bonds in the cis- form. The IUPAC numbering systems takes the carboxylic acid carbon as the first carbon atom. It is also common practice in Food Chemistry to count the carbon atoms from the other end of the hydrocarbon chain. Using this system the first double bond appears on the third carbon atom so it is known as an omega–3 fatty acid.
Evaluating the findings
DHA is widely promoted as a food additive (see advert on left). For example, the US National Library of Medicine, National Institutes of Health states states that DHA is good for people with a history of heart disease and also for promoting healthy brain development in children along with other claims (such as a lack of DHA in the brain being associated with the onset of Alzheimer’s disease).
Clearly there are strong commercial considerations when research into food supplements supports or contradicts such claims. If the reference above is scrutinized carefully it will be see that its two authors. L.A. Horrocks and Y.K. Yeo, work for Docosa Foods Ltd, 1275 Kinnear Road, Columbus, OH 43212-1155, USA. This does not mean that their claims are wrong but clearly they are likely to be putting the benefits of such a food supplement in the best possible light. If you look at the Wikipedia reference for docosahexaenoic acid it currently states that a citation is needed to support the claim that DHA supports healthy brain development in young children. This underlines the importance to the industry of the findings reported recently by McNamara et al.
McNamara and his team are obviously very much involved in research into the benefits of docosahexaenoic acid as they are currently carrying out a separate trial into its effect on children suffering from clinical depression. They are also looking at how effective it is to tackle attention deficit hyperactivity disorder (ADHD) in children. These trials are ongoing and the results have not yet been evaluated and published. Both the abstract (at no cost) and the full paper (for a small fee) that has been recently published by McNamara et al. on improvements in the concentration of young boys are available online. We teach students to evaluate their own work critically and for the need to repeat their experiments several times to ensure that the results are reproducible in order to give them validity. When dealing with purely chemical systems this usually presents few problems as the work can be reproduced by others using exactly the same conditions as there are relatively few variables to control. If different results are found then usually one of the variables has not been controlled properly1. The effect of food supplements on the human body is a very different scenario as no two humans are identical so there is much less control of the variables. McNamara’s conclusions on the effect of DHA on boys aged 8-10 are based on only 33 volunteers. Some of these were randomly given a placebo which reduces the number actually given the DHA. Those who received a low dose showed less change than those given a higher dose. The effect on the activation of the dorsolateral prefrontal cortex was determined using functional MRI. The question to be asked is how valid is such a small sample? This result will prove important to the food supplement industry. Statistically the sample is significant but should the sale of food supplements depend on such a small sample or should much larger trials be carried out before such significant claims can be made?
1. A good example of this is the addition of hydrogen bromide to asymmetric alkenes. In the early literature some researchers found the expected Markovnikov addition product, but others found anti-Markovnikov addition occurring. It was later realized that the alkene needed to be carefully distilled to remove the presence of peroxides in order to get only Markovnikov addition so that the only mechanism operating was electrophilic addition. In the presence of peroxides the faster free radical mechanism predominated.
Plant food or drug?
Posted on 07 June 2010 at 19:13h
Very sadly the BBC reported that two British students (aged 18 and 19) died on Monday 15 March 2010 after taking a substance called mephedrone. They were not doing anything against the law as at that time mephedrone had not been classified as an illegal substance. It was in fact sold as a plant fertiliser. As a result of these two deaths mephedrone was rapidly made illegal in the UK. The ban came into effect on 16 April 2010.
Mephedrone is interesting both from a chemical and from an ethical point of view.
A fertiliser?
Several websites legally advertised to sell the substance as a fertiliser before 16 April 2010. For example, plant-food.net1 and plantfeeders. They advertised it as a plant food. Interestingly enough some of them did not seem to sell many other types of well-known plant food and they specifically stated that the mephedrone was available in crystalline form with more than 99% purity whereas most of the other plant foods were sold as solutions etc. with little importance being given to their purity.
The benefit of phosphorus, nitrogen and potassium containing fertilisers is well known. Plant food sites claimed that mephedrone causes lush growth etc. but the science quoted was very vague. For example, the site miracle feedshad a question and answer section which contained the following:
"Can I use Mephedrone Plant Feed on my herbs growing on my kitchen window sill?
No! Mephedrone is a research chemical which works by infinitely diluting the key molecules with pure water which helps promote plant growth. However the chemical is untested and therefore it is strictly not for human consumption or for use on plants intended for human consumption.
Can I use Mephedrone Plant Feed on plants grown hydroponically?
Mephedrone is a research chemical which works by infinitely diluting the active molecules with pure water and was not designed for use in such an intensive system. Mephedrone works by promoting natural and spiritual growth. Therefore we would recommend Phostrogen Plant Food for this purpose."
…so mephedrone is a ‘research chemical’ which works by infinitely diluting the ‘active molecules’ promoting ‘spiritual growth’ in plants. Not very enlightening in a chemical sense.
Another site, plantfeeders, was a little better. It stated,
"It has been shown that mephedrone directly stimulates the key complexes within plant structure that ensure that leaves and stems are strong and mobile, enabling plants to maximise their light absorption and subsequently increase levels of photosynthesis, yield of sugar production and ultimately promoting healthy growth.”
However it gave no reference to “it has been shown."
The sites did say that the product was not for human consumption. It may therefore sound cynical, but is the reason that these sites were actively promoting the sale of mephedrone in a pure form because it had become a fashionable recreational ‘drug’ for young people?
A recreational drug?
Mephedrone has street names such as “M-Cat”, “MC”, "meow meow", "plant food" and "bubbles". During the past year it had become an increasingly popular substance taken by young people (some as young as 12) at night clubs and at universities. People who took it (either by snorting or in tablet or capsule form) reported that the effects were somewhere between methamphetamine (speed) and MDMA (ecstasy). It gives them energy, increases their heart rate and gives them a ‘feel good’ factor but is relatively short-lasting. It was an attractive alternative to illegal drugs in the UK before it was made illegal and currently there are no laws in many other countries governing its possession and use.
Chemical structure
So what is the chemical structure of mephedrone – is it chemically similar to adrenaline and amphetamines?
Its chemical name is 4-methylmethcathinone which is sometimes shortened to 4-MMC. It is also known as 2-methylamino-1-para-tolylpropan-1-one. It has the following structure:
It can be useful to give your students this structure and ask them what functional groups it contains and whether it does have similarities to the chemical structures of adrenaline and the amphetamines. This fits in neatly with assessment statement D.5.2 at both SL and HL in Option D: Medicines and drugs. The structures of just adrenaline and amphetamine are given in the IB data booklet and the structures of phenylethylamine, adrenaline, amphetamine, methamphetamine and ecstasy (MDMA or 3,4-methylenedioxymethamphetamine) are all given on page 345 of the second edition of my IB Chemistry Course Companion.
4-MMC contains a ketone, an aromatic ring, and is a secondary amine. Note that it also contains a chiral carbon atom and it is not clear whether the drug that is sold is one particular enantiomer or a racemic mixture.
Adrenaline and amphetamines such as methylamphetamine and designer drugs such as ecstasy (see structure below) are all derived from the phenylethylamine structure (shown on the left).
It can be seen that this is essentially also true for mephedrone as the –CH2- group next to the benzene ring has simply been oxidised to a carbonyl group (C=O). In fact apart from this difference and the fact that there is a methyl group in the 4- position (para-) on the aromatic ring the drug has an identical structure to methamphetamine (shown on the right).
It is therefore not surprising that mephedrone can mimic adrenaline and the amphetamines and cause effects such as increased alertness and a speeding up of heart rate.
Like many other drugs, mephedrone contains a basic amine group and the drug is often given in the form of its hydrochloride salt. This fits in well with topic D.9.4 on drug design for HL students studying the Medicines and Drugs option and also for both SL and HL students studying Option G: Further organic chemistry under G.8.3. It also relates to the separate page on Salt formation under novel uses for the data booklet.
More legal highs
One of the problems that governments have is keeping up with the number of legal new synthetic drugs that are currently being made (mainly in Asia) and imported into Europe and the US. The European Monitoring Centre for Drugs and Drug Addiction (EMCDDA) reported in 2009 that it had detected 24 new psychoactive substances through its international early warning system.
As exemplified above synthetic drugs like mephedrone can easily be designed to mimic the effects of other already banned substances. It would appear that most of these of these drugs are related either to the phenylethylamine structure of amphetamines or to cannabis related structures.
As the EMCDDA reports,
“The appearance of a large number of unregulated synthetic compounds…. specifically designed to circumvent drug controls presents a growing challenge to current approaches to monitoring, responding to and controlling the use of new psychoactive substances.”
Examples of how the structures of three other legal highs bear a striking resemblance to the structure of ecstasy can be found in another BBC article.
Ecstasy is the street name of 3,4-methylenedioxymethamphetamine (MDMA) and you can see from its structure (right) that it also is a derivative of phenylethylamine.
1 The web page advertising mephedrone for sale was removed once the drug was made illegal in the U.K. If you want to see how the company were advertising it then I have it saved as a pdf file 
.
Developments in MRI
Posted on 07 June 2010 at 06:48h
In the past year there have been two important new developments in Magnetic Resonance Imaging (MRI). 1H NMR was developed for use in body scanners by Nobel Prize winner Sir Peter Mansfield of Nottingham University, UK in 1973.
To avoid the use of the word ‘nuclear’ the technique is known as Magnetic Resonance Imaging. MRI and its uses are on the Chemistry syllabus under Assessment Statement A.5.2 in Option A: Modern analytical chemistry. By looking at the behaviour of hydrogen atoms in water in the body using non invasive radio waves in the presence of a strong magnetic field a scan can be built up to show abnormalities caused by diseases such as cancer.
1. A window into living breathing lungs
Researchers at Sheffield University have boosted the power of MRI by one million percent using a technique known as hyperpolarization. They have tested the new technique on 150 volunteers and used it to examine their lungs. In this way they have detected early signs of emphysema and revealed obstructions caused by cystic fibrosis and asthma.
2. Communicating with a person in a vegetative state
Perhaps even more amazing is that MRI has been used to communicate with people in a vegetative state. A team led by Dr Adrian Owen at the Medical Research Council Cognition and Brain Sciences Unit in Cambridge together with a team led by Dr Stephen Laureys at the Univerity of Liège in Belgium have reported that they have devised a technique which enables a patient in a vegetative state to say ‘yes’ or ‘no’ to a simple question. By thinking of playing tennis for ‘yes’ the motor activity part of the brain is stimulated and by thinking of wandering from room to room in his house for 'no' the patient stimulates the spatial awareness part of the brain. The different stimulations in the different areas of the brain can be detected by functional MRI (functional MRI works by detecting the changes in blood oxygenation and flow that occur in response to neural activity) and thus enable people who otherwise show no sign of consciousness to be able to communicate.
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