Letters - March 2009

Fun competition, flawed research

As a fellow of the Royal Society of Chemistry (RSC) I was angered to receive a request to sign a petition about examination standards. This was based on a seriously flawed piece of work, ie a competition using examination questions from the past 50 years.

Is this really the policy of the Society, developed and approved by its committees and councils? A learned society should be more rigorous in its approach. I have no objection to the competition itself - it was a piece of fun, it raised some interesting issues worth discussing further and it was profitable for some schools and students. However, to pretend that the competition was a significant piece of research is unscientific and risks alienating the two constituencies that the RSC most needs to influence, ie chemistry teachers and the Department for Children, Schools and Families (DCSF).  

I took my A-levels in 1959 and started teaching to the examination in 1964. At that time, the examination was largely based on rote learning and, in so far as there was problem-solving (and you could opt out of most of the problems, because there was a wide choice of questions), the problems fell into neat categories for each of which you could learn a strategy. Not having been trained in those strategies, most modern students did badly at the older O-level questions in the RSC's competition. 

The fact is, exam specifications (ie syllabuses) change over time. You cannot go back and test 1960s candidates on some 2008 questions. I embarked on A-level never having met the Periodic Table, or ideas of chemical bonding, or measured a rate of reaction. That would not be true of today's students.  

I recall arguing with a member a few years ago: '[Students] don't even know the colour of copper sulfate', he said. That's probably not true, but giving him the benefit of the doubt, I asked what colour neodymium nitrate was (actually a very pale lilac-pink). He didn't know, but would look it up if he needed to. What's so special about copper sulfate? If students need to know the colour of copper sulfate or neodymium nitrate, they can look it up and I suggest today's students would be much better at doing so than a student of 1960. There is more than one type of problem-solving, but the competition was loaded in that it only tested a narrow range of problems. 

Peter Borrows, Amersham Old Town

A-level chemistry - more demanding

I refer to the editorial in the last issue of Education in Chemistry, RSC on the campaign trail. While I cannot comment on the mathematical content of current GCSEs because it is not my area of expertise, I think the case made by the Royal Society of Chemistry (RSC), as far as A-levels stand, is much overstated. 

I think it would be more helpful and constructive to separate the mathematical demands and other issues. There is probably a good deal of truth in the assertion that the requirements of mathematical skills in A-level chemistry papers is less than it was 20 or 30 years ago (I started teaching A-level chemistry 40 years ago). There has also been a change of demand from the use of logs and slide rules to the use of calculators, which has brought with it less of a requirement to think about the mathematical steps undertaken. But it is a bit unfair to blame chemistry teachers for underlying changes in maths education. 

In terms of problem solving and critical thinking I do not feel that there has been a reduction in demand. In fact there has been a change in recent years in the opposite direction. In the Salters' A-level chemistry papers, for example, questions are always set in context, often a different context from those the students would have met in the 'chemical ideas'. The students are therefore required both to unravel the chemistry within the context as well as to understand and solve chemical problems. This is a much higher demand than responding to a straightforward chemistry problem asked in a similar way in each examination. The recent Salters' A2 questions are tough. 

Another area that perhaps the RSC has not fully considered is the response by students in investigations. Again Salters' A-level chemistry students are required to research, plan, carry out, analyse and evaluate their own investigation. This requires many of the skills that universities and employers say they value, and is far removed from a practical task that students of previous decades practised over and over again. 

Is this the response of a chemistry teacher in denial? It certainly doesn't feel like it to me. 

Derek Denby, Scunthorpe  

Solubility solved

As is not unusual when a Chatelierian approach is used, Almond's answer to Jolliff's question is inadequate.

The standard molar change in entropy (ΔS°) for dissolution in a solvent is an important factor in any solubility - the activity of a solute B in a saturated solution is given by an expression:

-RT log_e (a_B)_sat = ΔG° = ΔH° - TΔS° 

or its analogue for such cases as that of an ionic solute. Correspondingly, however, the ΔS° affects the solubility by a factor e ^ΔSo/R in (a_B)_sat - a factor which does not become either considerably more or less favourable if the temperature is altered.

The dependence of solubility on temperature is, rather, determined by an enthalpy change (ΔH).  The relation in terms of an activity, ie 

(∂log_e(a_B)_sat /T)_p = ΔH°/RT²

indicates unambiguously that the activity of the solute in the saturated solution increases with temperature if the ΔH° of solution is positive. Perhaps less obviously, it is the sign of ΔH for dissolving the solid in an almost saturated solution, and not the standard value ΔH°, which determines whether the concentration of the saturated solution increases or decreases with increase in temperature. An instance where the distinction is even qualitatively important is provided by the solubility of NaOH in water: the ΔH^oof solution is negative, while the concentration of the saturated solution increases with increase of temperature.

For Jolliff's question, it is important to consider what the solid is which is actually involved. If the measurements of the solubility relate to the solid hydrate Na₂SO₄.10H₂O(s), the concentration of the saturated solution increases as the temperature increases; if they relate to the anhydrous solid Na₂SO₄(s), the concentration of the saturated solution decreases as the temperature increases. An experimentally determined solubility usually relates to Na₂SO₄.10H₂O(s) at temperatures below about 32°C, and to anhydrous Na₂SO₄(s) at temperatures above about 32°C. The observed peak in the solubility of sodium sulfate(VI) at 35°C queried by Jolliff's student thus corresponds to two intersecting solubility curves, one for each of these solids - one curve with a positive slope and one with a negative slope - and not to a single solubility curve exhibiting a smooth maximum.

P. G. Wright, Dundee   

Look who's 'in denial'?

My initial reaction to the January Column article, RSC on the campaign trail, was to be uncomfortable with some of the assertions, and also challenged by the 'in denial' comment.

My own view is based on having taught chemistry at KS4 and KS5 since 1981. At KS4 this takes me from O-level and CSE chemistry through GCSE chemistry to GCSE double award science, and now the 21st century science course. And post-16, from doing JMB A-level myself, through teaching traditional London board, to Salters' A-level chemistry. 

Anecdotal though it is, my A-level chemistry involved, for example, learning by rote three industrial processes - the production of sulfuric acid, nitric acid and ammonia - and we knew one would come up in the final exam and could have a good guess at which one. The form of question was predictable - equations, conditions, equilibrium etc and I do frequently contrast this with my students today who learn about equilibrium but their questions will almost certainly be in a context they have never come across - maybe the industrial production of a medicine. In past decades practical work was prescriptive too, usually a titration (permanganate/oxalate). Today practical work is much more important and skilfully taught and learned.  

Thirty years ago the subject was dry - I had no model kits, no access to ICT, no Internet and, yes, log tables. Curriculum developments have brought the subject to life - textbooks are better written, better illustrated, with clearer explanations. Bodies like the Salters' Institute, the Nuffield Foundation, the Royal Society of Chemistry (RSC) and the Association for Science Education (ASE) have brought educationalists, academics and industrial researchers together to produce rich resources, as well as the opportunity to go on industry study tours and teachers' conferences.  

Although chemistry in HE has struggled periodically to recruit, this is more often to do with competition with other subjects. Often students think other subjects are easier, and they see little opportunity for career progression as well as a media view that chemists have spoiled the world, not helped to solve its problems. Thankfully the work shared between HE, schools and colleges, and the RSC (the programmes of widening participation and other RSC outreach projects for example) has started to show students chemistry is worthwhile - and perhaps they are realising that the intellectual and other challenges deliver them a very good qualification and potential career. 

At KS4 the changes are more difficult to map. There is no doubt in my mind that O-level chemistry and GCSE science are far apart - but surely this comes down to purpose and audience? Grade boundaries in O-level chemistry were very low, even for the higher grades and so the old O-level did feel very difficult and did put potential chemists off progressing - much was repeated in A-level.  

One matter of concern I do have is that in some of the very recent KS4 assessment models questions demand little narrative, and are merely a series of options and boxes to tick. This is easy to mark by a computer at a time when getting experienced or even inexperienced examiners might be difficult, and it offers consistency. But pupils do not learn material thoroughly because they can 'wing' it to an extent and the learning style does become very different. I think some pupils surprise teachers by doing well in an exam yet we know they find the subject hard. I have seen this affect post-16 work too and I am sure there is more room for more rigour.  

Maybe higher education will need more time to get students to the required competencies, including their level of maths - a price to be paid but one better than having fewer chemists which I think is my considered alternative. 

I dare say I am now in denial - but teachers are inspiring young people to study and succeed in chemistry. We have an eye on league tables but more importantly take a pride in those students we have inspired to enjoy, engage and study science (good), especially chemistry (better) and those who continue to use chemistry into a lifelong career (best). 

John Dexter, Nottingham 

Chemistry for all - the grand challenge

The November Column article Chemistry's grand challenges mentions concern that focusing on the Grand Challenges identified by the Engineering and Physical Sciences Research Council (EPSRC) consultation, may distract from responsive mode funding. But is there evidence that responsive mode funding suits everyone?  

Jessica Lober Newsome in her report The chemistry PhD: the impact on women's retention, published by the Royal Society of Chemistry (RSC) in 2008, writes: 'Women [in her study] reported that they would prefer if academic chemistry was more cooperative in nature... Increasing emphasis on interdisciplinary work, which by its very nature is cooperative... will provide a better environment for women'. 

The Grand Challenges with their focus on interdisciplinary collaboration may help address the grandest challenge still facing chemistry, to engage effectively with all sectors of society. 

 Paul Taylor, University of Warwick

Are we playing it too safe?

I write in response to the review of Sean Connolly's book Wholly irresponsible experiments! published in January's Reviews. The reviewer was worried about the safety of experiments designed to encourage children to do their own experiments with their parents at home. The example given was the use of a mildly caustic reagent without specifying eye protection. I have read through every experiment in the book and the only chemicals used are washing-up liquid, sodium bicarbonate, nail varnish remover and vinegar. I am concerned that we are constantly upping the precautions to be taken over the use of what are very mild chemicals. Should children wear safety specs before they wash their faces with mildly caustic soap? 

Many of us work hard to get young people to realise that chemistry is about everything that they use, not about dangerous chemicals in bottles in the lab. All of this is lost if students get the message that they have to wear safety specs to handle ordinary household chemicals. 

The idea of risk from chemicals seems to apply only when it's a chemistry experiment. If it was cooking or craftwork, the same precautions aren't seen as necessary. Can you imagine getting a risk assessment signed off by the H&S officer for an experiment which involved putting pieces of wet potato into oil boiling in an open pan. What precautions would he insist on - safety specs, heat-proof suit, fire brigade on hand? And yet chips are cooked at home every day of the week. It's only when it's chemistry that a fuss is made. This gives chemistry a bad name. 

Children do not have safety specs at home or in junior school. If they are told, by professionals, that eye protection is needed, they will not do the experiments. If we want children to do experiments themselves, we need to keep a sense of proportion over the use of safety specs.  

Please can we, as a chemistry community, agree that safety specs are not necessary when handling chemicals bought from the supermarket and freely available in the home. 

Lorelly Wilson, Knutsford