Video Transcript
The given chromatogram shows that
substance B has traveled further up the chromatography paper than substance A. What
properties of a substance affect how far it will travel up the chromatography
paper?
When we perform a chromatography
experiment, the first thing that we do is place our samples on the chromatography
paper. The particles in the sample get
adsorbed to the chromatography paper, which means they get stuck to it. But this adsorption is not
permanent. When we place the paper in the
solvent, which could be water or something else, the solvent will begin to travel up
the paper. As the solvent travels up the
paper, some of the particles in the sample will dissolve in the solvent and travel
up the paper with the solvent.
But what if the substance doesn’t
dissolve very well? Well, that means that it won’t
travel as far with the solvent as the solvent moves up the paper. So it seems that one factor that
definitely affects how far a substance will travel up the paper is the solubility of
the substance in the solvent. If it doesn’t dissolve in the
solvent very well, it won’t be able to travel as far. And if it dissolves really easily,
it will travel with the solvent as it moves up the paper very well.
Now, the other thing that’s going
on besides how easily the substance dissolves in the solvent is how attracted the
substance is to the paper. After all, adsorption is an
attraction to the paper. The substance is stuck to it. So if the substance is really
attracted to the paper, it won’t be able to move as far as the solvent travels up
the chromatography paper. And if the substance is not very
attracted to the paper, it will move more easily with the solvent. So the other property of a
substance that affects how far it will move up the paper is how attracted it is to
the paper. So knowing this, we can tell that
substance B either dissolves more easily in the solvent or it’s less attracted to
the paper than substance A.
