Oil and Water Density Polka Dotting

Oil and Water Density Polka Dotting

Oil and Water Density Polka Dotting 749 500 admin

Is your little artist ready to study pointillism? With this activity, we discover how to paint polka dots with colored water and oil (and subtly learn about density, too!).

What you need:

  • Oil (baby oil recommended)
  • Water
  • Dropper (pippette)
  • Food Coloring
  • Small bowls
  • Shallow bowl or pan


What you do:

First, pour water into various small bowls, the amount depending on how many different colors you would like to use. Add food coloring to the water and mix until they reach the desired color level.

Next, fill the shallow bowl or pan with oil. Use the dropper to squirt the various colors into the oil and create unique designs or pictures! Regardless of how much water is added, the two liquids will not mix.


Questions to consider:

  1. Why does the water not mix with the oil?
  2. Could this work with other liquids?
  3. Is there a way to force the two to mix? Why or why not?


Why it works:

Oil and water do not mix. This is mainly because of two reasons.

The first is that oil and water each have a different density. Oil is less dense than water, meaning that if you poured one into a cup of the other, the oil would settle on top of the cup with the water on the bottom. Only liquids with the same density can mix with one another.

The second is that water molecules are polar. This means that water molecules have a negative and positive side, making them more attracted to each other than the oil. This also causes the two not to mix.