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 an example of a practical to cover the mandatory practical requirement for Topic 5.1 under the heading of Enthalpy changes. 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%.