Introduction to Topic 11 and Topic 21

Topic 11 - Measurement and data processing - is really two completely separate topics under the one heading. The first two sub-topics deal with error and uncertainties (including graphing techniques) and the third sub-topic is concerned with spectroscopy. Topic 21 - Measurement and analysis is additional higher level material mainly on the identification of compounds and ¹H NMR spectroscopy splitting patterns.

Should measurement and data processing be on a chemistry syllabus? Personally I think that the chemistry syllabus should reflect real chemistry as much as possible rather than the sometimes arid and often simplified 'school' chemistry with little meaning to the real world. If you are working in CERN and measuring the velocity of neutrinos and claiming that you have found that they travel faster than the speed of light then clearly the uncertainties are of paramount importance (see blog on E = m(c + a little bit)². However, in a school where we use relatively simple but quite accurate equipment such as pipettes, burettes and an analytical balance (see image on right) are the uncertainties associated with them really relevant? Probably the only common measuring instrument you are likely to use when doing accurate work which does have a high degree of uncertainty is the simple thermometer - particularly when two readings are taken to measure a temperature difference which may only be accurate to ± 1 ^oC. For a temperature difference of 10 ^oC this equates to a ten per cent uncertainty. If you look at scientific papers in chemistry the error or uncertainty associated with results is often not given. Similarly virtually all data books (including the IB data booklet!), which often give values that disagree with each other, give no associated uncertainties with the data (see 'What is the true value' in the page 5.1 Measuring energy changes). It is sad to see Extended Essays in chemistry where a student has obviously spent hours working out all the uncertainties associated with the apparatus and yet not talked about the real uncertainties and assumptions behind his or her results. In fact sometimes their results and all their associated uncertainties are not even scientific as they have not been repeated and an average taken. The same is true of many Individual Scientific Investigation reports. Often the reaction does not go to completion, other products are formed, the products have not been properly purified and impure chemicals and solutions have been used to start with. The uncertainties caused by these are far greater than the uncertainties of the instruments used. Many teachers, and hence many students, are clearly confused about how to apply uncertainty calculations correctly and one wonders if your time might not be better spent on a topic with a more obvious chemistry bias.

However the other parts of Topic 11 and 21 are clearly extremely important and it is so good that they now form part of the core programme. Understanding the basics of spectroscopy will benefit so many of you in your future studies - not only in chemistry but in medicine and other scientific disciplines. The ability to deduce an unambiguous structure by analysing spectroscopic data is a real skill and a good application of logical deduction.