Create a liquid rainbow!


1. A few paper cups (As many as the number of food colors + one more)
2. Water
3. Food color (It would be good if you use all the seven colors of rainbow)
4. Salt
5. A transparent tube about a foot long with a bit small diameter
6. A funnel that will fit in the transparent tube
7. Some scotch tape or duct tape


1. At first add an equal amount of water to each cup.
2. Then add a few drops of food coloring to each cup.
3. Add no salt to the first cup.
4. Add two tablespoons of salt to the 2nd cup.
5. Then add four tablespoons of salt to the third cup.
6. Raise two more tablespoons of salt for the next cup, two more for the next cup and so on.
7. Now stir the salt added cups with spoon.
8. Use scotch tape or duct tape to seal up one end of the tube.
9. Now check out your record to see which one of the colored solution has the most salt in it.
10. Use the funnel to pour some of that solution into the tube to 1 inch.
11. Then pour about 1inch of the solution that has the 2nd greatest amount of salt in it.
12. Continue pouring rest of the different colored solutions into the tube like this. And also remember to pour the colored solution in descending order of the amount of salt. For example, the mixer with the first greatest salt poured first, mixer with 2nd greatest salt poured second etc.
13. Now observe and write down what the water tube looks like.


If the colored solutions are poured in the proper order the many different colors should not mix.


Each of the different salt solutions has different works. Some solutions are lighter than others and some solutions are heavier than others. The heavier solutions will go bellow the tube and the lighter solutions will tend to float on the mixer of solutions. That’s why the colors will not mix with each other because they have different density. If you are careful enough to pour the solutions in  order of density you can create a rainbow of liquids.


If you leave your liquid rainbow untouched long enough eventually all the colors would mix. Actually the solutions start mixing with each other as soon as they come in contact with one another. That problem is solved by using a tube with small diameter. It actually minimize the amount of contact between two solutions.


1. Use a tube with wider diameter to see what happens.
2. See what happens if you invert the transparent tube very quickly.
3. Use a stopwatch to see how long it takes the colors to mix in the tube (It would be better if you observe this for both small diameter and big diameter tube)


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