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
Links and Resources
This resource is somewhat dated but still contains some useful ideas and activities. Ideas have changed little since this book was published and so the activities are as valid and modification of the basic procedures is quite possible. The resource contains both a teachers' guide and student book and is included here for ideas rather than as a photocopiable resource that can be used directly with students.
In this activity students measure the pH of a variety of different substances using universal indicator. This is an activity that could be done early on in a module of acids and bases in order to introduce the idea of pH and the use of indicators, and in particular universal indicator in the estimation of pH. Teacher notes and a student worksheet are included in the resource.
This is an interesting simulation that enables students to measure the pH of a number of common substances and look at the effect of diluting substances with water. The simulation allows students to go deeper and to investigate the relationship between hydrogen (hydronium) ion concentration and pH and to look at absolute and molar ratios of hydroxide and hydrogen ion at given pH values. A sophisticated simulation that can take students from the basics of pH to ideas that are A Level standard without being mathematical. It is a versatile resource that can be used selectively at various levels of understanding from relatively basic to the more complex.
This resource is a collection of video clips showing the reactions of acids with metals, oxides and carbonates. It draws out a number of important ideas and in particular that acid behavior depends on the presence of water by showing the reaction of calcium carbonate with pure ethanoic acid and with aqueous ethanoic acid.
This resource gives a detailed analysis of acid-base behavior and includes sections on each of the three main definitions of acids and bases, Arrhenius, Bronsted-Lowry and Lewis, as well as some less known definitions. This is not designed as a student resource but may be found useful as a quick reference to the various theories of acids and bases for teachers planning lessons in this area.
This resource contains student notes with instructions of how to carry out the neutralisation of sodium hydroxide with hydrochloric acid using a titration. The resulting solution of sodium chloride is then evaporated to dryness to obtain crystals of the salt adding another tier of interest.
In this activity students react a limited range of metals with three different acids and isolate the compounds formed. This might be a nice activity to introduce the idea of the reactivity of metals with acids. This area of the syllabus overlaps with reactivity series where the reactions of metals with acids is one way of investigating the differences in reactivity of metallic elements.
This simple investigation uses titration to investigate indigestion tablets. As it stands, the resource guides students toward assessing which of a range of tablets is most effective by a semiquantitative method. In other words, by simply measuring how much of a specific acid solution each tablet will neutralise. Students then calculate the cost benefit ratio for each tablet in order to decide which is the better value. Students who have covered chemical calculations could extend the investigation to calculate how much of the active ingredient a tablet contains and so the resource is modifiable to suit the abilities of different groups. At its most basic level it could be used to introduce neutralisation against the background of a familiar context.
This video models an approach to investigating neutralisation using a pH probe and following the changes in pH using ICT. This is a very nice idea that starts with a consideration of what acids and alkalis are and moves on to what is happening in neutralisation of an acid with a base. Overall a really nice approach to investigating neutralisation and titration curves.