Lab 2A: Chromatography
1. Why is it important that only the wick and not the filter paper circle be in contact with the water in the cup?
It is important than only wick be in contact with the water in the cup because you don't want to saturate the entire filter paper with water. The way chromatography works is that the components/pigments will be absorbed into the paper and travel at different rates due to their different physical properties and tendency to attract to the paper/water. As the water slowly moves out from the wick, pigments will be picked up and then absorbed and be allowed to travel and end at different rates. Without this gradual spread of water, the pigments wouldn't spread, and would stay black.
It is important than only wick be in contact with the water in the cup because you don't want to saturate the entire filter paper with water. The way chromatography works is that the components/pigments will be absorbed into the paper and travel at different rates due to their different physical properties and tendency to attract to the paper/water. As the water slowly moves out from the wick, pigments will be picked up and then absorbed and be allowed to travel and end at different rates. Without this gradual spread of water, the pigments wouldn't spread, and would stay black.
2. What are some of the variables that will affect the pattern of colors produced on the filter paper?
Some variables that affect the pattern of colors produced on the paper include the type of pen being used and the pigment that makes up the pen's color, how long the wick touched both the water and the filter paper, the patterns that were drawn on the filter paper, and the size of the hole in the filter paper the wick was placed in.
Some variables that affect the pattern of colors produced on the paper include the type of pen being used and the pigment that makes up the pen's color, how long the wick touched both the water and the filter paper, the patterns that were drawn on the filter paper, and the size of the hole in the filter paper the wick was placed in.
3. Why does each ink separate into different pigment bands?
Since the black ink is made up of different pigments and each pigment has different properties that allow them to be absorbed more/less quickly into the filter paper, each pigment will stop at around the same area and different will travel farther.
4. Choose one color (e.g. yellow, red, or blue) that is present in more than one type of ink. Is the pigment (compound) that gives this color always the same? Do any of the pens appear to contain common pigments? Explain.
A color present in more than one type of ink is red. The pigment/compound that gives this color is always the same, because when comparing chromatograms made by the same pen, this red pigment seems to be around the same area of the filter paper. Another example is a bright blue seen around the edges of many of the chromatograms; this shows that the pigment stopped at the same place, meaning it has the same properties. This common area that the red and bright blue show up in on different filter papers also proves that multiple pens contained common pigments.
A color present in more than one type of ink is red. The pigment/compound that gives this color is always the same, because when comparing chromatograms made by the same pen, this red pigment seems to be around the same area of the filter paper. Another example is a bright blue seen around the edges of many of the chromatograms; this shows that the pigment stopped at the same place, meaning it has the same properties. This common area that the red and bright blue show up in on different filter papers also proves that multiple pens contained common pigments.
5. Why are only water-soluble markers or pens used in this activity? How could the experiment be modified to separate the pigments in "permanent" markers or pens?
Only water soluble markers or pens were used in this activity because in order for the pigment to spread, it needed to be able to dissolve/become a homogeneous mixture with the water. If it was not water-soluble, meaning it could become a solution with water, the water would be unable to spread the pigment. Using rubbing alcohol in place of water could work with this experiment if using permanent markers or pens, since permanent ink is soluble in alcohol.
Only water soluble markers or pens were used in this activity because in order for the pigment to spread, it needed to be able to dissolve/become a homogeneous mixture with the water. If it was not water-soluble, meaning it could become a solution with water, the water would be unable to spread the pigment. Using rubbing alcohol in place of water could work with this experiment if using permanent markers or pens, since permanent ink is soluble in alcohol.
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