Separating mixtures GCSE - includes paper chromatography

This lesson is the third in the atomic structure scheme of work for the 2016 AQA specification. The two previous lessons are on elements, compounds and mixtures and balancing equations. The theme of the lesson is separating cannabis chemicals in order to extract TetraHydroCannabinol (THC). This is part of a group of chemicals called 'cannabinoids' and is used as an oral spray called Sativex that treats multiple sclerosis. The lesson starts with students listing 3 reasons for and 3 reasons against legalising cannabis. There is a YouTube video showing a 3 minute BBC News report that is embedded. The link is included in the PowerPoint. Students then use the separating mixtures trump cards to state what method they would use for each stage of extracting THC. They carry out a RSC practical to extract 'THC' (it is in fact a combination of chemicals) using a pestle and mortar and the solvent propanone. Though not included in the RSC practical they could filter the solvent to remove any solids. They then use paper chromatography to see whether their sample has a pure chemical. If the chemical is pure there will be a single spot visible on the chromatogram. Students could then dry their chromatograms and calculate the Rf value of their spot. Finally a higher level question is included at the end where students consider the effect of using different solvents. Please rate these resources and leave feedback.