Worksheets and lesson ideas to challenge students aged 11 to 16 to think hard about filtration and crystallisation (GCSE and Key Stage 3)
Filtration allows us to separate an insoluble solid from a liquid or solution. Students will have studied filtration at primary school, so it’s worth thinking about how we should build on this knowledge and not just repeat information. Ask students to draw particle pictures to show how filter paper works. Make sure all students can fold filter paper correctly – do a challenge to see who can folder the paper the fastest! Can students use terms such as filtrate and residue correctly? Making and separating a precipitate, made from sodium hydroxide and copper sulphate solution, can be a great practical to use.
Filtration and crystallisation – separating soluble salts
KS3 practical activity to separate salt and sand. This practical is an open activity that asks students to come up with their own method to separate salt from sand. To increase the challenge, students should be allowed to select the apparatus they want to use. It’s worth pointing out the difference between evaporation and crystallisation – i.e. leave some water for crystallisation to take place in. At the end of the practical the percentage yield of each group is calculated and a winner declared. You could use this method for teaching about preparation of solution salts. (PDF)