In this lab, for which a supplemental video is available, I walk through the process of taking 8 seemingly identical black water based markers, and through a process called chromotography, separate the inks in the markers into their individual chemicals, showing that they are indeed, NOT identical.
This process shown is an extremely basic example of the methods used by forensic scientists to identify substances found at crime scenes....without the million-dollar machines.
I've used the lab with great success in a 7th grade class. I have each group do one marker (random) in a beaker, then compare with another group, in order to draw conclusions.
The lab takes a while (just WAITING), so I typically work on other class content with the kids, stopping every 5 minutes or so, so they can make observations. The ink will rise up the paper for hours, but the lab portion can be cut off whenever needed, to fit your time frame.
If used with higher grade levels, you can easily get 4 chromotography strips into a 400mL beaker.
The materials you'll need include:
-Chromotography paper (either in roll, or strip format)
-My informal lab report (my store)
- (x) number of black, water-based markers
-a beaker for each group (I use 400mL beakers)
-a paperclip per group