Chromatography is the physical separation of a mixture into its individual components. This lesson integrates mixtures, solutions & solubility into an activity where students will identify the solute & the solvent. Because chromatography can be used to separate the components of inks & dyes, students are able to identify the unique "recipe" that makes up the mixture of a specific brand of pen. After the students are taught the ink chromatography technique, the fun can continue with a mini forensic investigation, "The Case of the Celebrity Dog-napping".
Step 1: Gather the Needed Materials (coffee Filter, Pencil, Beaker, Water Soluble Pen/marker, Water)
Step 2: Cut a Strip of Filter Paper From the Coffee Filter and Using the Marker Draw a Thick Line Near the Bottom of the Filter Paper- About 1/4 Inch From the Bottom.
Once this is completed, carefully attach the strip to the pencil in order to suspend the strip over the water in the beaker. Make sure the ink does not touch the water-only the bottom of the filter paper should touch the water.
Step 3: Allow the Water to Move Up the Paper for Approx. 5 Minutes and Then Remove the Strip From the Water
The video clip allows you to see the separation of the ink as the water "walks" up the filter paper.
After about 5 minutes, hang the chromatogram on the side of the table to dry. This can then be taped to the attached worksheet if you choose to use it.
Step 4: Students Should Identify the Individual Colors in the Chromatogram That Make Up the Markers Unique Mix of Ink.
Attached is a great worksheet that can prompt students as they move around the room comparing chromatograms.
Step 5: Once Students Have Mastered the Technique Its Time to Put Their Skills to the Test in "The Case of the Celebrity Dog-napping"
Set-up for this culminating activity is relatively basic. You'll need 3 suspect water soluble pens of the same color but different brands.
Step 6: Label the Pens As Different Suspects (you Can Have a Lot of Fun With This Using Teacher Photos and Profiles or Different Celebrity Nemesis). the Most Basic Would Be #1, 2, & 3
Step 7: Write the Ransom Note on a Piece of Filter Paper in One of the Suspect Inks.
Isn't it convenient that the dog-napper used coffee filter paper? :) Each lab team can get their own note or a slice of the same ransom note (more realistic). Attached is the story & activity my students complete. This is a great activity that can also cross the curriculum into government, creative writing, etc.