With this lab, students will observe osmosis! To set up this lab all you need is water, cornstarch, a ziplock bag, and iodine tincture (available at grocery stores!). the cornstarch water is sealed in the bag and placed in the iodine water mixture. After a few hours, the iodine passes through the cells of the bag and reacts with the cornstarch. The cornstarch cells are too large to pass through the bag, so the iodine mixture does not change color.