In this activity, students will use color and various liquids to learn about density.

Materials Needed

Per small group (1-4):

1 tall, clear jar with a lid
Cup to mix food coloring into liquids
Spoon or stir stick
Dropper

Enough to fill ¼ – ½ inch of the jar:

Honey
Light corn syrup
Dish soap (blue or green)
Olive oil
Rubbing alcohol
Water

Enough to share:

Food coloring

Steps:

Pour some honey into the middle of the jar, being careful not to touch the sides. Use enough to create a full layer in the jar.
Mix corn syrup with some food coloring, using a cup and spoon. (Avoid using the color that matches your dish soap.)
Pour the colored corn syrup into the middle of the jar.
Pour dish soap into the middle of the jar.
Rinse out your cup, then mix water with a different color of food coloring, and pour that into the middle of the jar.
Pour a thicker layer of olive oil into the middle of the jar.
After rinsing the cup, mix rubbing alcohol with another color of food coloring, but wait- don’t pour that into the middle of the jar! It’ll mess up your rainbow!
Using a dropper, gently add the colored alcohol to the edges, being careful to keep from penetrating the olive oil layer.
Observe the layers and the lovely rainbow, noting how the differing liquid densities create them. Take one last look before you move on to the next step. (Note- if you want to maintain the colored layers of your Rainbow Jar, stop here.)
Put the lid securely on your jar, and then shake it up.
Set the jar down and watch what happens. The food coloring will likely not recover, but observe the way the different liquids behave.

Explanation:

All the liquids in your jar each have different weights and they each have a different number of molecules floating around in them. We call this density. The liquids with less molecules are lighter and stay at the top of your jar. The liquids with more molecules are heavier and sink to the bottom of your jar.

Which liquid is the heaviest? How about the lightest?

Real World:

Density is what makes balloons float! The gas that you put in balloons is helium. Helium is lighter than air, so balloons float!