ChemistryChapter 19: Chromatography
Preparing the Paper
Cut a paper strip about 2-3 cm wide.
Learning objectives
- State the main idea of preparing the paper in clear words.
- Explain why preparing the paper is useful in chemistry.
- Apply the correct method, observation, equation, or comparison.
- Avoid the common mistakes and write a complete exam answer.
Definition
Cut a paper strip about 2-3 cm wide. Draw a baseline about 1.5-2 cm from the end in PENCIL, not ink. Ink would dissolve and run with the sample. Put a tiny concentrated spot on the line with a capillary tube. A large blot streaks.
Important terms
- 2-3 cm
- Cut a paper strip about 2-3 cm wide.
- 1.5-2 cm
- Cut a paper strip about 2-3 cm wide.
- PENCIL
- Cut a paper strip about 2-3 cm wide.
- not ink
- Cut a paper strip about 2-3 cm wide.
- tiny concentrated spot
- Cut a paper strip about 2-3 cm wide.
- capillary
- Cut a paper strip about 2-3 cm wide.
Overview
Pencil and spot size both matter:
Baseline in Pencil
Pencil graphite does not dissolve in the solvent, so the start line stays put. Ink is a mixture of dyes: it would chromatograph too and ruin the run. Keep the line 1.5-2 cm from the bottom so it sits above the solvent later.
Examples HB pencil line · No ballpoint · Line above the liquid
The Spot
Use a capillary to load a tiny concentrated spot. Let it dry for a few minutes. If you need more sample, add another tiny drop on the same point after the first is dry. A large wet blot spreads sideways and streaks.
Examples One pin-head spot · Dry, then a second touch · A big blot: streaks
WHAT — Core idea
Cut a paper strip about 2-3 cm wide. Draw a baseline about 1.5-2 cm from the end in PENCIL, not ink. Ink would dissolve and run with the sample. Put a tiny concentrated spot on the line with a capillary tube. A large blot streaks.
WHY — Why it matters
Width about 2-3 cm is enough to hang straight without wasting paper. Label the top in pencil as well, so you know which strip is which after drying.
HOW — Method, evidence, or comparison
1. 1. BASELINE IN PENCIL: Pencil graphite does not dissolve in the solvent, so the start line stays put. Ink is a mixture of dyes: it would chromatograph too and ruin the run. Keep the line 1.5-2 cm from the bottom so it sits above the solvent later. 2. 2. THE SPOT: Use a capillary to load a tiny concentrated spot. Let it dry for a few minutes. If you need more sample, add another tiny drop on the same point after the first is dry. A large wet blot spreads sideways and streaks.
HOW — Answer in an exam
PENCIL, not ink. Tiny dry spots, not a puddle. The baseline must stay above the solvent when the strip is standing in the cylinder.
Explanation
Width about 2-3 cm is enough to hang straight without wasting paper. Label the top in pencil as well, so you know which strip is which after drying.
In simple words
PENCIL, not ink. Tiny dry spots, not a puddle. The baseline must stay above the solvent when the strip is standing in the cylinder.
Key points
- 2-3 cm
- 1.5-2 cm
- PENCIL
- not ink
- Pencil
- does not dissolve
Exam preparation
Exam Focus
Quick revision
Revision Zone
Review the key facts, formulas and checks before you move on.Preparing the Paper
Sticky Notes · Quick Revision
WHAT
- Cut a paper strip about 2-3 cm wide.
Key Points
- 2-3 cm
- 1.5-2 cm
- PENCIL
- not ink
- tiny concentrated spot
HOW
- Pencil graphite does not dissolve in the solvent, so the start line stays put.
- Use a capillary to load a tiny concentrated spot.
Example
- HB pencil line
- No ballpoint
- Line above the liquid
Common Mistake
- Draw the baseline with pencil, not ink, because ink may separate and spoil the result.
Exam Tip
- PENCIL, not ink.
- Tiny dry spots, not a puddle.
60-second revision
- Cut a paper strip about 2-3 cm wide.
- Draw a baseline about 1.5-2 cm from the end in PENCIL, not ink.
- Pencil graphite does not dissolve in the solvent, so the start line stays put.
- Use a capillary to load a tiny concentrated spot.
- PENCIL, not ink.
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