Want to make your own rainbow? In this simple science experiment, kids can build their own rainbow in a jar while exploring density, mass, and volume.
Watch our demonstration video, gather your supplies, and print out our detailed instructions to get started. An easy to understand explanation of how it works is included below.
- Tall Glass Jar
- Food Coloring: Red, Blue and Green
- 1/4 cup Honey
- 1/4 cup Blue Dish Soap
- 1/4 cup Water
- 1/4 cup Olive Oil
- 1/4 cup Rubbing Alcohol
- Jars for mixing and pouring
- Teaspoons for mixing
Step 1 – Add one drop of red food coloring and one drop of blue food coloring to 1/4 cup of honey and stir until combined. This creates a purple color liquid. Pour the purple liquid carefully into the tall jar.
Step 2 – Next add about 1/4 cup of blue dish soap to the tall jar.
Step 3 – Add a few drops of green food coloring to 1/4 cup of water and mix until combined. Then, carefully pour the green liquid into the tall jar. Tip: When pouring in the green liquid, tilt the jar so the liquid runs down the side of the jar slowly.
Step 4 – Wait a few moments and then slowly pour 1/4 cup of olive oil into the jar. Again, be very careful when pouring in the liquid. Make sure to tilt the jar and pour very slowly so the colors don’t mix.
Step 5 – Add a few drops of red food coloring to 1/4 cup of rubbing alcohol and mix until combined. Then, carefully pour the red liquid into the tall jar. Tip: I can’t stress enough how important it is to tilt the jar and pour slow. Otherwise, the colors will mix together and you won’t get a distinct rainbow.
Do you know why you were able to make the liquids form the rainbow in a jar? Find out the answer in the how does this experiment work section below.
Density is the reason that this experiment works! Density is a measure of how much mass (or “stuff”) there is in a given volume. Density is a ratio of mass to volume and can be found by dividing an object’s mass by its volume (D=m/v).
Based on this equation, if the mass of something increases but the volume stays constant, then the density increases. Also, if mass decreases but the volume stays constant, then the density decreases. Density is all about how tightly packed the matter making up the material is in a given volume. Lighter liquids (like olive oil and rubbing alcohol) are less dense than heavier liquids (like honey and dish soap) because they have less matter in a given volume. Because olive oil and rubbing alcohol are less dense, they will float on top of liquids like water, dish soap, and honey. Liquids with a lower density will always float on top of liquids with a higher density.
All liquids have their own unique density. Water has a density of 1 g/mL (g/cm3). Objects will float in water if their density is less than 1 g/mL. Objects will sink in water if their density is greater than 1 g/mL.
I hope you enjoyed the experiment. Here are some printable instructions: