Diffusion lad Questions???????!!!!!?

Question

We did a lab where we put startch in a zip lock bag and iodine in a Beaker. we but the startch in the beaker and left it for an hour. after that the startch turned black.


So these are the Questions and please explain im so confused.

Based on your observations which substance moved. the iodine or startch?


How did you determine this


What if you did the oppisite?>

Answer 1

1. The starch turned black. That's what happens when you put iodine on starch. So the iodine must have come into the bag in order to make the starch black.
2. If the starch had moved, the black would be outside the bag. The iodine must have moved.
3. If you put the starch on the outside of the bag and the iodine on the inside of the bag, the iodine would still move through the bag and the starch would not. (Starch molecules are too big to pass through the bag, but the iodine molecules are much smaller.) So the iodine would go through the bag and the starch would turn black outside the bag.

It's actually a very dark blue instead of black, but you get the idea.