Question

prepwork part 1:
directions: read the scenario below and answer the questions that follow.
oswald, the octopus that sits on ms. davies’s desk, has gone missing! in his place, someone has left a note,
containing a list of demands for his safe return. ms. davies can only think of two options: caving to the thief’s
demands or figuring out who did it before the deadline.
the note was written in black marker. fortunately, all of the black markers in ms. davies’s room are labeled to
identify who they belong to. unfortunately, there are several black markers scattered on the table near where the
note was found and it is not obvious which one was used to write the note.
because ms. davies has studied chemistry, she knows that each type of black marker has a slightly different
combination of pigments in the ink. based on this, she thinks she can come up with a plan to determine which
marker was used to write the note.

1. **what separations technique could be used to determine the pigments used in each marker?

justify your response.

1. **what property of the pigments is this technique based on?
2. once all of the markers have been tested, how will ms. davies be able to determine which one was

used to write the note?

Explanation:

Question 1

To determine the pigments in marker ink, paper chromatography is suitable. It separates components in a mixture (ink pigments) based on their differential movement through a stationary phase (paper) by a mobile phase (solvent). Marker ink is a mixture of pigments, and chromatography can separate them to identify the composition of each marker's ink.

Paper chromatography relies on the different affinities (attraction) of the pigments for the stationary phase (paper) and the mobile phase (solvent), and their different solubilities in the solvent. Pigments with higher solubility in the solvent and lower affinity for the paper move faster, while those with lower solubility and higher affinity move slower.

After testing all markers with chromatography, Ms. Davies can compare the chromatogram (the pattern of separated pigments) of the ink from the note with the chromatograms of each marker's ink. The marker whose chromatogram matches the note's chromatogram (same number of bands, same positions/colors of bands) is the one used to write the note.

Answer:

Paper chromatography. It can separate the mixture of pigments in marker ink by using a solvent to carry the ink components up the paper; different pigments move at different rates, allowing their separation and identification.

Question 2