Amount of substance

The section on amount of substance revises, builds upon and extends the work students will have done on the mole concept and chemical calculations at GCSE. Balanced chemical equations are usually given for all but the simplest of reactions. Students will be familiar with many of the types of manipulation in this section such as calculation of empirical and molecular formulae, reacting mass calculations, molar volumes and calculations on solutions, but will very often need further practise and consolidation to become confident.

Students are expected to have a much clearer understanding of the mole as a concept and these resources will help with that. Although they will have met the idea of molar volume at GCSE, this is extended at A level to include the ideal gases equation (pV = nRT).

In addition, problems at A level will frequently require application of ideas from different areas in order to arrive at a solution to one problem. For example, a question may start as a reacting mass type problem, but then require calculation of the concentration of a product gas which is dissolved in a given volume of water. Questions that require switching from one tool to another in this way is one of the reasons that students can find this area of the syllabus difficult. It is crucialy important for this reason that students can clearly identify the 'type' of problem that is being posed at each stage of the process so that they are able to select the correct approach from their 'toolkit'.

The resource list draws together a number of activities to provide practise in this area of the syllabus and includes both theory and practical activities designed to place the concepts and skills required in an interesting context.

Whilst this list provides a source of information and ideas for experimental work, it is important to note that recommendations can date very quickly. Do NOT follow suggestions which conflict with current advice from CLEAPSS, SSERC or other recent safety guides. eLibrary users are responsible for ensuring that any activity, including practical work, which they carry out is consistent with current regulations related to Health and Safety and that they carry an appropriate risk assessment. Further information is provided in our Health and Safety guidance.