Acids and bases
The resources in this list cover acids, the nature of acidity and alkalis (or more broadly, bases). At GCSE students learn that acids form hydrogen ions when dissolved in water and that alkalis contain hydroxide ions.
Students are expected to understand the concept of pH as a measure of acidity or alkalinity. At higher level, students should understand that pH is a measure of the concentration of hydrogen ions in a solution and also to have a basic understanding that pH is a logarithmic scale in terms of the pH changing by one unit when the hydrogen ion concentration changes by an order of magnitude (factor of ten).
Students need to develop a familiarity with how pH is measured using indicators or a pH probe, and the pH scale itself.
Many students find the difference between concentrated and dilute, and strong and weak, difficult to understand, so its useful to stress to students that in chemistry strong does not mean concentrated as it does in common language.
These resources also cover the reactions of acids with metals and with carbonates and neutralisation as the reaction of hydrogen ions and hydroxide ions to form water.
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
pH Scale *suitable for home teaching*
This is an interactive simulation in which students can test the pH of various substances. There is also an option to switch to the macro version which allows students to visualise what happens during dilution on a molecular level although this would be too advanced for many GCSE students.
Secondary Science Using ICT: Investigating pH Using a pH Probe
This video shows how a pH probe can be used during a titration to show how the pH change can be observed in real time. The video is a little dated but is still well worth watching to show how this technology works.
