TITLE: Introducing Chromatography
AUTHOR: Helen K. Kloepper, Louisburg Elementary/Middle
School; Coffeyville, KS
GRADE LEVEL: 6-8
OVERVIEW: Students will learn to set up a chromatography
lab in preparation for the GEMS Unit, "Crime Lab".
PURPOSE: To familiarize students with the lab set-up for
the chromatography unit and introduce the vocabulary
necessary for the "Crime Lab" unit.
MATERIALS: many different colors and brands of markers,
filter paper cut into 2.5cm. x 10cm. strips, tape, pencils
or drinking straws, small clear plastic cups (2 per group),
magnifying lens, solvents (I use rubbing alcohol and water),
data sheet to tape results on.
ACTIVITIES AND PROCEDURES:
Chromatography is a method used to separate mixtures.
In this lab the ink in the markers will be tested to see
what colors were used in the ink.
In this activity the students choose five markers to
test. They will need the markers, 2 plastic cups filled
with 40 ml of solvent each (I use water in one and rubbing
alcohol in the other. Other solvents that can be used are
vinegar and ditto fluid), two pencils or straws to suspend
the filter paper from so that it can hang in the solvent,
and a data sheet to tape their results on.
1. Student should make a line with each marker
approximately 4cm. from the bottom of the filter paper.
Each marker will be tested in both the water and
alcohol so two pieces of filter paper will be used for
each marker.
2. The top of the strip of paper is attached with tape to
a pencil or straw.
3. The paper is suspended in the solvent so the end just
touches the solvent. The ink line should NOTE be in
the solvent, the line should be 1-2cm. above the
solvent.
4. Remove the filter paper when the solvent has traveled
2-3 cm. up the paper.
TYING IT ALL TOGETHER:
As the solvent travels through the test substance some
of the test substance will be attracted to the solvent and
follow it up the filter paper. Since different molecules
will be attracted and move different distances the inks will
separate. The results will be bands of different pigments.
Some are quite surprising!
I like to use this lab the day before I do the GEMS
"Crime Lab Chemistry". The students are then able to get
the lab set-up for the "Crime" and know how I want the
results, data, reported. The GEMS unit contains information
on how to set up a lab to investigate the ink found on a
ransom note and also a candy smudge found at the scene of a
crime. I have used both and found them to be very
interesting and great fun, especially if you get some of the
office staff to be suspects in the "crime".
GEMS "Crime Lab" is published by the Lawrence Hall of
Science, University of California, Berkeley, CA 94720.
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