The Lost Cross and Mandatory Lab 6.1

Mandatory Lab 6.1 refers to ‘Investigation of rates of reaction experimentally and evaluation of the results’. Here, in the UK, I have been introduced to a new way of carrying out the ‘lost cross’ experiment with respect to changing the temperature. The experiment is a classic. A solution of sodium thiosulfate is added to hydrochloric acid. Over time, a precipitate of sulfur is produced: 2HCl(aq) + Na2S2O3(aq)  --> 2NaCl(aq) + SO2(g) + S(s) + H2O(l) The initial rate of reaction can be measured by timing how long it ...

The Mandatory Labs / Skills: Topic 5.1, A Calorimetry Experiment for an Enthalpy of Reaction

Over the last couple of months I have posted some ideas of lab work for you to help with the mandatory labs or mandatory skills that the IB has stipulated are carried out over the duration of the IB course. So far we have looked at labs for deducing the empirical formula of compounds, examples of titration labs and labs to calculate the Mr of a substance using the ideal gas equation. This months post will take up where the others have ...

Mandatory Lab Ideas, Topic 1.3, Titrations

Last month's post focused on the mandatory lab covered in section 1.2, ‘The obtaining and use of experimental data for deriving empirical formulas from reactions involving mass changes’. This month, I thought I would carry on with this theme and focus on the second mandatory lab found in topic 1.3, namely ‘use of the experimental method of titration to calculate the concentration of a solution by reference to a standard solution’. Personally, I think titrations form the nuts and bolts of the ...

Mandatory Lab Ideas, 1.2, Empirical Formula

As you well know, the IB now tells us that we must carry out up to twelve mandatory labs or skills (I say up to as there is some debate whether 9.1, the application of the Winkler method is mandatory or not and the ‘single replacement labs’ occur twice, in 15.1 and 19.1). So I thought I would focus the next few blog posts on some of these mandatory labs, starting with the first on one the list, namely, topic 1.2, ...

Getting your practical programme together

Hopefully, by now you will have had time to reflect on the new course and start thinking about your practical programme (PSOW). It is my intention of this blog post ot give you some ideas of things you can add to your PSOW. Are you aware of the ten mandatory labs / skills that you are expected to teach your students? These are listed in the guide ….. but they are not very clear. If you look at the biology guide you will ...