Examples of databases

A good example of a database in action is when GLC is combined with a Mass Spectrometer in the analysis of blood or urine to determine whether an athlete has taken a banned substance. After the components have been separated by GLC (gas liquid chromatography) each one is then separately passed through the Mass Spectrometer. In the past it would have taken a long time to match each spectrum mIB Docs (2) Teamally with a book containing the mass spectra of all known substances to identify all the components. Now the information is all stored on an integrated computer and it is done automatically so that the spectrum is not even required – instead a print out simply lists all the components present and the percentage amount of each.

Chemists are well served with databases. Perhaps the best starting point for an IA exercise is the one produced by the Royal Society of Chemistry. Not only does this have many data sheets and bases and interactive programmes, it also has many links to other sites with good databases. It is self-explanatory and you can get students to carry out some of the interactive exercises. These include shapes of molecules and ions, indicators and calculating lattice enthalpies using Born-Haber cycles for a vast number of ionic compounds. All of these are on the core or AHL and in one sense you do not really need more than this. You can also provide individual exercises such as plotting a graph of 2^nd Ionization energies of the elements against atomic number and comparing it with the more usual plot of 1^st Ionization energies against atomic number. To continue on the theme of periodicity you can ask students to plot other factors such as density, melting point, boiling point, etc. to see how periodic these properties really are.

One topic where databases are really useful is Topic 11.3 (and 21.1) - Spectroscopic identification of organic compounds where students are unlikely to have good access to actual spectrometers. You could give them a series of compounds and ask them to predict the main absorptions/peaks etc. in their IR, ¹H NMR and Mass Spectrum then get the students to retrieve the actual spectra from a database and compare the two. There is probably scope for some good 'hands off' Individual Scientific Investigations here. There are many databases of spectra. Perhaps the best free one is organised by the National Institute of Advanced Industrial Science and Technology (NIST). This includes the ¹H NMR, IR and Mass Spectra of thousands of compounds and also includes spectra from spectroscopic techniques not on the IB syllabus such as ESR, ¹³C NMR and Raman.

One exercise you could give students is with infrared spectroscopy. They can see from the IB data booklet that IR absorptions occur in a range (e.g. C=O occurs between 1700-1750 cm^-1). They should also know that the precise absorption depends on the neighbouring atoms attached to the functional group. By selecting a variety of compounds and determining the precise absorption from the database they can see whether any patterns emerge.

Another good database which is continually updated is the one produced by NASA’s Eyes on the Earth concerning climate change. This contains much information on sea levels, atmospheric carbon dioxide concentrations, land and sea temperatures and ozone ‘holes’.

A good source of 64 different free chemistry databases has been put together by Richard Apodaca, whose company, Metamolecular, creates innovative solutions to chemical information problems. This list can be used to provide much fertile material for the Internal Assessment.

Many students are now using WebMO as the basis of their IA. WebMO gives students immediate access to five of the best known and comprehensive databases and it allows students to run state-of-the-art computational chemistry programs from the web-browser on their computer. For a brief introduction as to how WebMO works it is worth spending 35 minutes looking at the video WebMO for IB Chemistry produced by James Midgley.

  WebMO for IB Chemistry

James would be the first to say that he is only just getting to grips with how this programme works. It has a lot of potential but it should be noted that users need to be aware of a few pitfalls. Students need to look critically at the information they obtain. For example, you will note that after about ten minutes James changes butane at one point into but-1-ene by adding a double bond between the first two carbon atoms and taking away two hydrogen atoms. However because the page has not been refreshed it does not accommodate this and is still stating the carbon atom is sp³ hybridised, the bond angle is 109^o and the bond length is 1.54 Å (i.e. 0.154 nm , the length of a C-C single bond). It is also important not to 'go round in circles'. For instance it is a nice exercise to change the bond length and get the programme to work out the new energy associated with it and then to plot the graph which gives the actual bond length at the lowest energy. However the values can be obtained directly by a student straight from the the graph in the LibreTexts book without the need of the database so it is not suitable for a good IA exercise. There is one more worrying problem which has been reported by some teachers. When IAs using WebMO have been sent for moderation, the moderation factor is more wildly unpredictable. Moderators tend to either mark up, as they are astounded at the content, or they massively mark down as they do not understand what they are reading. The IB needs to address this problem.