The plastic baggie was permeable to which substances?

The plastic baggie was permeable to Iodine.

Explanation:

The plastic bag is a good example of the cell membrane as it is semipermeable. Experiments show that a plastic bag is semipermeable. Take corn starch nin a plastic bag and dissolve it in water. Now take a beaker with water and add Iodine indicator. The colour changes to brown.

Place the plastic bag inside the beaker. After some time the colour of the starch solution turns blue from white. But the solution in the beaker is of the same colour. This shows that the plastic bag has numerous tiny holes and thus acts like a semipermeable membrane allowing Iodine to pass through it. Apparently it retains the large starch molecules from passing out.