Worksheets and lesson ideas to challenge students aged 11 to 16 to think hard about acids, alkalis and salts (GCSE and Key Stage 3)
For many students the acids and alkalis topic marks the beginning of their chemistry course. It is here that they find out that similar substances can be grouped together based on their chemical reactivity, and that chemicals can be detected using analytical techniques such as indicator paper. The topic also represents a great example of how scientific theories change and develop during history. I think it is worth using formulae early on so that students become familiar with symbols such as HCl, NaOH and H2SO4; familiarity breads confidence!
The pH Scale
GCSE activity on the human pH scale. Students create a human pH scale by lining up in the classroom holding numbers -1 to 14. Other class members place different substances on the scale. This is a great exercise to assess prior learning – it could be used before any lesson on pH or acid/base chemistry. Slides showing pH of 0 and -1 are available if you feel brave enough to explain that pH is a measure of hydrogen ion concentration (pH=-log10[H+]) and can therefore be negative. (PDF)
Reactions of acids
GCSE and Key Stage 3 practical activity on reactions of acids. Students plan and carry out an investigation to identify a series of unknown substances. They must use their knowledge of reactions of acids. Students react unknown carbonates, metals, metal oxides and metal hydroxides with HCl. They test the products and use this information to identify the substances. It challenges students to problem-solve and think about reactions of acids rather than simply learning equations. (PDF)
Making an insoluble salt
GCSE practical activity on preparing an insoluble salt. Students are challenged to produce a white precipitate of barium sulphate floating in a colourless solution. They work together to devise a method to produce the insoluble salt, using only HCl, NaOH and copper (II) sulphate. This is a great activity as it makes assessment of learning visible. This resource was contributed by Sana Badri. (PDF)
Preparing a soluble salt
See our page on separating techniques for an activity to separate NaCl from a mixture.