Vitamin C Makes Iodine Disappear

1. Vitamin C Makes Iodine Disappear Materials: Dilute iodine/starch mixture; vitamin C solution What you do: Add vitamin C solution dropwise. What students see: Dark color fades/disappears. Question: Where did the color go if we didn't dilute it much? 2. Bendy Potato Osmosis Materials: Potato strips pre-soaked in fresh vs salty water What you do: Compare stiffness/bendiness. What students see: One strip becomes firmer, another limp. Question: Why did the same potato become different? 3. Fixed vs Movable Pulley Materials: Pulley setup; rope; small load; spring scale What you do: Lift same load with fixed pulley and movable pulley. What students see: Movable setup requires less pulling force but more rope. Question: Where did the 'saved force' go?

Predict → observe three demonstrations → compare what changed → choose independent activity station → cleanup/share. Guiding questions: Question: Where did the color go if we didn't dilute it much? Question: Why did the same potato become different? Question: Where did the 'saved force' go?