This growing rainbow chromatography pots of gold activity is a super low-prep STEM activity that demonstrates capillary action, cohesion, and adhesion!
In this St. Patrick’s Day STEM activity, the water moves up the paper towel pieces through capillary action, the tendency of small tubes (like those in the paper towel) to draw liquid up into them against the force of gravity due to the attraction of water to molecules in the sides of the tubes.
The purpose of this activity is to show kids how adhesion, cohesion, and surface tension can cause a liquid to move up a porous solid as well as demonstrate the basic concepts of chromatography!
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Chromatography Rainbow Pots of Gold Supplies
- Black Plastic Cauldrons (We grabbed ours from the Dollar Tree!)
- Paper Towel Strips (We used one paper towel and cut it into strips)
We used black plastic cauldrons from the Dollar Tree, one paper towel cut into strips, colored the end with marker, and water.
The Science Behind Rainbow Chromatography
This activity is an example of chromatography. Chromatography is a process that scientists use to separate, analyze, or purify mixtures.
Capillary action makes the marker dye move up the paper towel. The molecules in the water stick to each other. This is called cohesion. Then, the water molecules stick to the paper towel. This is called adhesion.
As a water molecule starts to climb up the paper towel, the next water molecule starts to climb up the paper towel. This is because water molecules are polar molecules that bind together.
Water is a polar molecule because electrons in the hydrogen atoms are pulled toward the electrons of the oxygen atom.
As the water moves upward through the paper towel, it lifts the washable marker dye molecules with it. Because the washable markers are water based, the marker dye disperses in water.
WANT TO USE PERMANENT MARKERS?
A permanent marker is not water soluble and will not work in this experiment. In order to use a permanent marker, you can substitute isopropyl alcohol as the solvent. Remember to wear the appropriate safety gear when working with alcohol and work in a well ventilated area.
STEM Career Connection
A forensic scientist is a scientist who studies evidence left at a crime scene. Forensic scientists often use chromatography to separate a mixture into its individual parts.
Using chromatography, components of a mixture can be separated. The individual components are carried different distances by a solvent as it moves up paper.
Forensic scientists use retention factor to compare and make determinations about the individual components. This helps them to solve crimes!
Chromatography Rainbow Pots of Gold Steps
To get started, arrange the five pots. Fill the pots slightly with water. I probably put 2 tablespoons of water in each pot.
Cut your paper towel into strips. Next, use your markers (rainbow colors) to color the ends of each strip.
TIP: Add lots of marker to the ends, you want a good amount of dye to travel up the paper towel.
Leave a small space white at the end of the strip to absorb the water up the strip. This will make sure that the color runs up instead of down into the pot.
Put one end of the paper towel into the first glass and the other end into the glass next to it. Repeat this step between each of the pots of gold.
Observe the water climb up the paper towels. Talk about what you see!
CONNECT THIS CHROMATOGRAPHY Demonstration WITH OTHER STEAM BUCKETS?
Check out these STEAM extension ideas for this chromatography experiment!
Use the NCES Kids’ Zone Bar Graph to graph the results of the retention factor for each of your markers.
Environmental Engineers use chromatography to test groundwater and other substances and develop solutions from the results
Try the activity over again and mark the filters at the center with different colored markers or draw designs. Then fold the coffee filters out from the center to make colored flowers and attach them to popsicle sticks.
The retention factor is the ratio of how far the ink traveled compared to how far the liquid traveled. Measure the distance the liquid has traveled as well as the distance each color of ink has traveled. Repeat the calculation for every marker. Graph your results.
SOME BOOKS TO READ WITH YOUR ACTIVITY
We love incorporating books into our activities. Here are some great books about detectives and solving crimes to read with your activity!
- The Boxcar Children Books by Gertrude Chandler Warner
- Nancy Drew Mystery Stories by Carolyn Keene
- Cece Loves Science by Kimberly Derting and Shelli R. Johannes
- Women in Science: 50 Fearless Pioneers Who Changed the World by Rachel Ignotofsky
Meet Toni, the Maker Mom behind Our Family Code
Hey there, I’m Toni! I’m a software engineer and Maker Mom that finds my joy in unleashing my children’s curiosity by exploring STEAM concepts with my fantastic five!
When I’m not chasing toddlers or raising tweens, you can find me tearing things up and putting them back together over here at Our Family Code.
I am the owner and content creator of multiple educational websites designed to increase access to STEAM & STEM education with a focus on teaching computer science and coding to kids of all ages!
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