Moving Iodine

Good morning scientists! We just discovered that we can make Iodine move without touching it. Want to find out how? Try this experiment with your little scientists.



Bottle of Iodine (Found in the Pharmacy area of store)


Large Plastic Storage Bag

Small Plastic Storage Bag (The cheaper the better your results)


Optional: Baking Sheet or Tray (To set your experiment in just in case it leaks)


**Note Iodine will stain skin and clothing, use caution. Do not eat or drink in a lab setting. Wash thoroughly when done**

  1. Have your little scope several spoonfuls of cornstarch into the small plastic storage bag. You want a nice layer across the bottom of the bag. Seal the bag completely getting most of the air out as your close it up.
  2. Place the small plastic bag inside the larger plastic bag and pour iodine into the large bag. **I poured in the iodine rather then my little scientist** Seal the large plastic storage bag completely. Let the bag sit for an extended period of time out of reach from children and pets. (We waited several hours).
  3. I’d recommend this being an adult only step. Carefully retrieve the small plastic storage bag from the iodine solution. (I gently rinsed mine off to limit mess). You should see dark purple/black color in the cornstarch, this is where the iodine entered the small plastic bag.

Talking Points

This investigation simulates the movement of particles across a cell membrane. The Cell membrane is the thin outer-layer of a cell, in out investigation the small plastic bag represented the cell membrane. When a substance travels across the cell membrane from higher concentration (area with more) to lower concentration (Area with less) it is called diffusion. In this experiment iodine particles were able to move across the cell membrane (small plastic bag) from the outside where there was a higher concentration of iodine to the inside of the bag where there was a lower concentration of iodine.

Cornstarch is an indicator or a substance that has a change if a specific substance is present. Cornstarch acts as an indicator for iodine. When iodine touches the starch it changes the starch to a dark purple/black color like we seen in our experiment.


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