Chromatography Investigation
Aim: To use chromotography separation to identify a unknown mixture.
Equipment:
Safety Information
• Strips of chromatography paper
Handle using forceps or gloves and
wash hands after handling
• Pencil
Glassware – risk of cuts if broken
• Beaker
Apply pressure to wounds and inform
teacher immediately
• Water
• Pipette
• Drawing pin
• 3 black pens (different brands)
• 1 chromatogram of an unknown black ink spot
(made with 1 of the 3 pens being tested)
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Chromatography Investigation
Method:
Step 1: Using the first pen, make a small spot at one end, about 1 cm from the edge. Make sure you
know which pen this chromatogram relates to.
Step 2: With the drawing pin, secure the other end of the strip to the middle of a wooden pencil and
balance across the top of the beaker.
Step 3: Using the pipette, add water to the bottom of the beaker so that the paper is submerged but the
black ink spot remained above the water line. Ensure you do not splash the paper, or allow it to touch
the sides of the beaker.
Step 4: Observe as the water is drawn up the paper. When it has reached the top, carefully lift out the
paper using the pencil and lie flat to dry.
Step 5: Repeat steps 1 to 4 again for each of the other pens.
Step 6: Once dry, compare your chromatograms to the unknown and identify the pen used.
Questions
1. What is a mixture?
2. The ink is soluble in water. What does this mean?
3. What is the solvent that is being used in this investigation?
4. Describe how chromatography is used to separate the dyes in the ink.
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Chromatography Investigation
Answers
1. What is a mixture?
A mixture is made up of two or more different compounds, not chemically joined.
2. The ink is soluble in water. What does this mean?
The ink can be dissolved in the water.
3. What is the solvent that is being used in this investigation?
Water.
4. Describe how chromatography is used to separate the dyes in the ink.
The dyes in the ink will dissolve into the water and are pulled through the paper at different
rates. Some dyes are more soluble and will travel through the paper further. The different dyes
will form spots at different distances depending on their solubility; the dyes become separated.
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