Osmosis and Diffusion demonstration | Iodine starch experiment with bag | Science Experiments | elearnin | Chemistry demo | Diffusion and osmosis in plants explanation | Diffusion and osmosis in cells explained | Diffusion and Osmosis definitions | Diffusion and Osmosis though a semi permeable membrane

This experiment shows the movement of particles through a membrane
For this experiment you will need:
• Water
• Starch solution
• Iodine
• Dropper
• Zipper plastic bag
PROCEDURE:
• Mix the starch solution in the water in a beaker.
• With the help of the dropper put some iodine solution in the zipper bag.
• Zip the plastic bag.
• Now turn up side down to check whether there is any leak.
• Submerge the plastic bag into the beaker with starch solution.
• Leave the arrangement for half an hour.
• A layer of deep purple-black color layer is formed on the membrane of the plastic bag and the color slowly diffuses into the starch water.
EXPLANATION:
Iodine is used to test for the presence of starch. When Iodine reacts with starch, it turns deep purple-black.
The iodine molecules are small enough to pass through the membrane of the plastic bag, however starch and water molecules are too big to pass through the membrane.
The movement of the iodine through the plastic membrane is functionally the same as movement of molecules through biological membranes, that is, any cell membrane. The molecules will move from higher concentration to lower concentration. Osmosis is the net movement of solvent molecules (in this case, iodine) through a partially permeable membrane (like a plastic bag) into a region of higher solute (water) concentration, in order to equalize the solute concentrations on the two sides.
Here, by partially permeable membrane or semi-permeable membrane, we mean a permeable to the solvent, but not the solute.
Diffusion is that physical process in which any solvent moves, without input of energy, across a semi permeable membrane separating two solutions of different concentrations.