Line up five glasses. Add 1 tablespoon of sugar to the first glass, 2 tablespoons of sugar to the second glass, 3 tablespoons of sugar to the third glass, and 4 tablespoons of sugar to the fourth glass. The fifth glass remains empty.

 

Add 3 tablespoons of water to each of the first 4 glasses. Stir each solution. If the sugar does not dissolve in any of the four glasses, then add one more tablespoon (15 ml) of water to each of the four glasses, or heat water briefly in the microwave.

 

Add 2-3 drops of red food coloring to the first glass, yellow food coloring to the second glass, green food coloring to the third glass, and blue food coloring to the fourth glass. Stir each solution.

 

Now make a rainbow using the different density solutions. Fill the last glass about one-fourth full of the blue sugar solution.

 

Carefully layer some green sugar solution above the blue liquid. Do this by putting a spoon in the glass, just above the blue layer, and pouring the green solution slowly over the back of the spoon. If you do this right, you won't disturb the blue solution much at all. Add green solution until the glass is about half full.

 

Now layer the yellow solution above the green liquid, using the back of the spoon. Fill the glass to three-quarters full.

 

Finally, layer the red solution above the yellow liquid. Fill the glass the rest of the way.

 

The sugar solutions are mixable, so the colors will bleed into each other and eventually mix.

 

If you stir the rainbow, what will happen? Because this density column is made with different concentrations of the same chemical (sugar or sucrose), stirring would mix the solution. It would not un-mix, like you would see with oil and water.