Sharon Endebak

Deep Purple Magic

Science Concept:

Likes dissolve likes. Polar and non-polar compounds do not dissolve.

Materials:

separatory funnel

0.05 M liquid iodine solution

10 mL graduated cylinder

100 mL beaker

methylene chloride

Directions:

1. Measure 2 mL of 0.05 M iodine solution and dilute with 75 mL of water.

2. Pour into separatory funnel.

3. Measure 6 mL of methylene chloride and pour slowly into the separatory funnel.

4. Shake the funnel with the stopper on.

Introduction:

The iodine in this funnel is not completely happy because it cannot decide where it would like to go. Does the iodine prefer to stay in the water or would it rather move to a new liquid which is methylene chloride.

Which liquid does iodine prefer to dissolve in?

Explanation:

The iodine is not very soluble in water because the water is polar and the iodine is non-polar. The water is has a yellow/orange color from the iodine that is dissolved in it. When the methylene chloride is added to the water, it falls to the bottom of the funnel because it is more dense than the water and iodine mixture. The methylene chloride is also not soluble because it is also non-polar. The methylene chloride extracts the iodine from the water. The methylene chloride dissolves the iodine preferentially because they are both non-polar. Likes dissolve likes. The iodine thus shows it's true purple color in this solution.

Safety:

Use caution when using liquid iodine, as it will stain clothes and skin.

Disposal:

Dispose of the purple iodine/methylene chloride in the halogenated waste container in the organic chemistry lab. The water can then go down the drain.

Reference: Unknown