I picked up a copy of ‘Periodic Tales’ recently by Hugh Aldersey-Williams. It’s a Sunday Times bestseller and a great read.
It’s divided into five parts : power, fire, craft, beauty and earth. The book can be dipped into and I picked a great chapter about the use of chromium and cadmium compounds in paints. There was a fascinating story about how 150 pounds of the fluorescent pigment zinc cadmium sulphide was dropped from a plane on Norwich in 1963. The Ministry of Defence wanted to investigate how biological agents would spread if dropped from height. Although it is considered safe there is still some debate about the long term health effects associated with the study. There are so many great stories in this book, as the Sunday Telegraph says ‘ Aldersey-Williams is full of good stories and he knows how to tell them well ‘ .
I’ve also joined a book club – now this is not just any book club but the Chemistry World book club !
This month it’s Michael Gordin’s book Scientific Babel which examines the history of scientific language, may be one for the Christmas stocking !
So as we all know, there’s not a class that doesn’t benefit from a chemistry sing-a-long and it got me thinking what is your favourite chemistry song ? Here is one that my A level pupils swear is the best way to remember electronic structure …
I spotted this video clip on the Chemistry World Twitter feed. Recently I blogged about graphene and it looks like it now can be considered an active material. The material is actually graphene oxide-polydopamine layers deposited in a pattern onto a graphene oxide base. The folding affect is caused by water in the structure evaporating when IR light is shone on the material. The researchers inspiration apparently came from nature and the behaviour in plants. I could watch this video clip all day it’s mesmerising !
Do you ever feel left out, you have missed a trick or if only you had known something sooner ? Well, I spotted something on Twitter recently and when I read the link it felt that a lightbulb went on ! The article in question was about the theory of the chemical triplet. Ask any chemist about triplets and their first response will inevitably be based around NMR and splitting. But this theory is fundamental to the teaching of chemistry and was introduced by Johnstone in 1991. It identifies the idea that there are three levels when teaching chemistry – macroscopic, sub-microscopic (is that nanoscopic then ?) and symbolic which can also be referred to as descriptive, explanatory and representational. (Diagram from RSC)
I found an excellent research paper on this theory ( I’ve attached the link below). It looks at three teachers with different experience and levels of knowledge of triplet theory. One of the teachers believes that the topic dictates which teaching triplet is most important, for example the macroscopic level to teach acids or symbolic to teach equilibrium. Another believes that the topic should always be introduced through macroscopic everyday examples. One of the teachers believes that particle theory, particle models, particle diagrams are the essences of the microscopic level of triplet relationship. I found this interesting as recently I tried a different approach to teaching redox. I asked the pupils to carry out simple experiments such as displacement and burning magnesium which they would be confident completing.
Instead of asking for observations which would be an intrinsic part of a normal practical I asked them to draw diagrams showing electronic representations of the atoms/ions of the reactants and products to see if they could work out what was happening before embarking on constructing the symbol equation representations. Little did I realise at the time I was moving between all three levels. Whether it improves their understanding will be seen with their topic test.
Triplet theory holds resonance with me as I have always felt that chemistry involves a leap of faith – we are asking our students to relate macroscopic observations which they can see to sub-microscopic behaviour that they can’t. This is probably one of the largest hurdles a chemistry teacher has to overcome but it is a journey they have to make on their own. Pedagogic content whilst training is for the most part generic and does not focus on subject mastery. Continuing professional development is also very much linked to the school’s development plan leaving little focus on subject mastery. The importance of social media and organisations such as the RSC and ASE cannot be underplayed as they reach out to teachers and provide material and ideas to develop their subject mastery.
This is a quick post about polyethylene terephthalate. Basically we found this brilliant ad for terylene by M&S and I decided that I would have to share it with you (is it just me or have Gap adverts been inspired by this). Polyethylene terephthalate is the forth most common synthetic polymer and it pops up as ‘terylene’. The advert shows that it’s cultural history is as interesting as its chemistry ( apparently ranked 87 in the most important British innovation of the twentieth century). Terylene was seen as the material of its time, discovered and patented by Whinfield and Dickson in 1941, it’s first commercial use was in 1948 when it was used to make lace curtains. Watch the advertisement above and see just what a revolutionary material terylene was – the promise of a hardwearing, crease resistant material seemed too good to be true and of course it was ! The big problem with terylene is that it is waterproof and during the summer it can be an uncomfortable material to wear as it does not absorb sweat like cotton does. Now natural fibres such as cotton and linen are seen as much more desirable as they are seen as sustainable and are considered to be carbon neutral.
Interestingly, polyethylene terephthalate is also used as the world’s packaging choice for many foods and beverages because it is hygienic, strong and lightweight. Check any soft drink bottle and you will see the PET symbol indicating that it is made of polyethylene terephthalate. The starting materials for this plastic are oil based but it can be recycled. The European recycling rate is 57% and it is the most recycled material. Demand for PET is rising with polyester and food and beverages industries determining market behaviour. At present annual world wide production of PET is approximately 40 million tonnes with 65% used to make fibres, 5% for film and 30% for packaging. Polyethylene terephthalate is made by the polymerisation of benzene-1,4-dicarboxylic acid and ethane-1,2-idol. This makes pelts of the polymer which are then melted and squeezed through fine holes to form a fibre (terylene). To make PET used in plastic bottles, the pellets are further heated to a molten liquid stage and the polymer chains stretched in two directions. The polymer is then cooled quickly while it is stretched, the chains are frozen with their orientation intact leaving an extremely tough material.
Looks like this polymer will continue to shape our world – Apple announced this week that they have been developing ways to make their phone screens shatterproof and one patented idea is to use tabs to surround the phone to act as shock absorbers with the suggestion that they could be made from polyethylene terephthalate. So it looks like the exam board have missed a trick using the term ‘terylene’ in the specification, polyethylene tetraphthalate is so much more than a dated clothing fibre !
Last week I read an article in the Daily Telegraph with interest – it’s seems a homeopathy conference in Germany descended into chaos when attendees took remedies that contained hallucinating properties. The police are investigating whether the attendees knowingly took the drug which had been banned in Germany in 2014. The molecule in question is a member of the amphetamine family – and this got me thinking – how does a molecule be considered legal or illegal ? Molecule of the Month has an excellent article about methyl amphetamine and the story of the British skier Alain Baxter. In 2002, he was the first British skier to obtain an Olympic medal for alpine skiing but was stripped of his bronze medal after failing a drug test due to L-methamphetamine. It had been present in his decongestant, and has no stimulant activity but was on the Olympic banned substance list. However its optical isomer, D-methamphetamine, is the illegal stimulant commonly known as speed. In this case the only difference in these molecules is their stereochemistry – connectivity, molecular formula, physical and chemical properties are all the same.
Another interesting molecule is cathinone which has a structure very similar to amphetamine with the only difference being a carbonyl group. It is found in khat leaves and is considered a cultural norm in South East Asia where up to 20 million people take it each day.
However, elsewhere in the world it is a controlled substance and the appearance of 4-methylmethcathinone in the UK as a legal high under the name ‘Meow meow’ made headline news with reports of a cluster of deaths. At present the UK are in the process of bringing in the psychoactive substances Bill which will ban all ‘legal highs’ . In a very interesting article in the Guardian the point was raised that the bill will mean the researchers and pharmaceutical companies will have huge obstacles if they wish to study the therapeutic effects of these molecules. It uses ketamine, a drug that has therapeutic properties but is a controlled substance due to its recreational use, as an example. The recreational mood altering effects have been investigated and it has been found that ketamine may be a fast acting antidepressant.
Of course banning molecules is nothing new, with probably the most famous case being prohibition where the ban of alcohol in the USA lasted from 1920 to 1933. This new law will state that if a molecule alters your brain function it will be banned but substances such as alcohol, tobacco, caffeine, food and medical products will be excluded from the scope of the Bill. This seems like a sweeping statement but it is an attempt to stop the chemical modification being carried out by distributors of legal highs. The problem at present is if a molecule is identified as being problematic, for example 4-methylmethcathinone, the data that needs to be collected before it can be banned is so time consuming that newly modified versions can be created and marketed to fill the hole left once the original drug is banned. The discovery of 4-methylethcathinone on the market illustrates this problem. This molecule is an analogue of methylcathinone, with a slight modification of an ethyl group on the amine, but with similar psychological and behavioural effects. The hope is that this Bill will address the cat and mouse game being played but it looks like there will be major debate before it is passed.