Some time ago I wrote a question for an IB exam and the markscheme essentially said “If they give the answer ‘yes’ and this reason award the marks; if they give the answer ‘no’ and give this reason (a different reason) award the marks. The question was rejected by the external examiner with the comment, “In Chemistry there is always a right answer we cannot have an either or answer”. This approach to chemistry worries me.  It doesn’t seem a problem with other subjects, e.g. History where there are many different answers to “Discuss the causes of the First World War”. There are many areas on our syllabus where the chemistry is extremely questionable and evidence can be found to both support and refute the statements made. If we are serious about testing Objective 3 where students need to construct, analyse and evaluate then these areas can provide fertile ground for assessing students understanding and encourage them to think much more critically about what they are learning.   

For example, both Option B and Option F have sub-topics on Fats and Oils (although in Option B they are called lipids). One of the statements made (F.2.5) is that mono- and poly-unsaturated fats are healthier for the heart than saturated fats and another (B.4.4) asks students to state the importance of omega-6 and omega-3 fatty acids. The generally held view (i.e. the ‘right’ answer) is that switching from saturated fats to unsaturated fats high in omega-6 (linoleic acid) and omega-3 (linolenic acid) will lower the risk of death from coronary heart disease and cardiovascular disease.  There have been several studies in the past that have questioned the validity of this claim. Recent research has now shown that in the case of omega-6 the reverse is actually true – increasing the amount of omega-6 you consume is bad for your health. The data used is not new as the research was carried out in the late 1960s and early 1970s in Australia. The trial involved 458 men aged between 30 and 59. What researchers from several universities writing in the British Medical Journal have done is to re-evaluate this data and they have shown that switching from saturated animal fats to omega-6 polyunsaturated vegetable fats leads to an increased risk of death not only from cardiovascular disease and coronary heart disease but also from all other causes. This is bad news for the margarine industry which for decades has been promoting margarine high in omega-6 as good for your health (see image). Sources of omega-6 include safflower oil, corn oil, soybean oil, sunflower oil, and cottonseed oil.  The research does not report any findings on omega -3 which is present in fish oils. Some researchers, e.g. Eduardo Siguel,  claim that what is important for health is a high omega-3:omega-6 ratio rather than vice-versa. Clearly much more research needs to be done and our syllabus would be better served by a discussing the evidence for and against the claims rather than just dogmatically stating that “poly-unsaturated fats are healthier for the heart than saturated fats”.