Why not sweeten lessons by experimenting with sugar? At key stage 3 pupils could learn basic filtering by starting with brown sugar, adding water and warming with activated charcoal. Watch their amazement as the black messy solution filters to a clear solution, left to evaporate and produce white sugar crystals (even better from beet!) At KS4 pupils often test for protein, carbohydrate, fat and sugar with various test solutions. For sugar this involves Benedict’s test (blue to orange when heated) but why not test some real foodstuff. My favourite would be a few ml of concentrated sulphuric acid into a 50ml beaker of slightly damp sugar to convince of the dehydrating hazards of concentrated sulphuric as the black volcano grows (illustrating C6H12O6 becomes a foamy charcoal and steam) but do use a fume hood and care. Finally, at KS4 or KS5 use urine “clinistix test strip” which contains glucose oxidase and goes from blue to purple with glucose to investigate an enzyme reaction (vary the temperature, pH, substrate and even a few poisons!)