Year 9 looked at the effect of temperature on the rate of diffusion using potassium manganate crystals. They then took different foods such as cheese puffs and bread flour and filled some dialysis tubing with solutions on the crushed food. They found that iodine solution could diffuse through the dialysis tubing and colour the food blue/black.
This showed us that although the iodine was able to diffuse through the tubing, the starch molecules in the food were too big to get through the microscopic pores in the membrane. There was quite a lot of fun comparing rice crispy juice with cheese puff juice!