Loading…
Loading…
Loading…
Edexcel GCSE Chemistry · 1CH0
Edexcel 1CH0 · 2.11 Check the specification (PDF) (opens in a new tab)
Ink is a mixture: it can contain several coloured dyes dissolved in a solvent. This core practical has two parts because the dyes and the solvent tell us different things about its composition. separates the dyes to produce a . separates pure water from a suitable water-based ink. Neither part alone gives the full picture.
Chromatography reveals the dyes in ink; distillation collects its water while the dyes remain behind.
Draw a line in pencil near the bottom of a strip of chromatography paper. Put a small spot of ink on the line; if you have known dyes or other inks for comparison, put separate spots of these along the same line. Keep the spots small and apart. Suspend the paper in a beaker containing a shallow layer of water, or another suitable solvent. The bottom of the paper must touch the solvent, but the pencil line and ink spots must stay above its level. Pencil is used because its mark will not dissolve and move with the solvent as an ink line might.
The solvent rises through the paper and carries dissolved dyes with it. Different dyes travel different distances because they differ in how readily they dissolve in the solvent and how strongly they are held by the paper. Remove the paper before the solvent reaches the top and immediately mark the furthest point reached by the solvent: the solvent front. Let the chromatogram dry, then record the colours and positions of the spots. More than one separated spot shows that the original ink contained more than one dye. Comparing its spots with known samples can help identify the dyes; matching colours alone is less reliable than comparing their positions under the same conditions.
Put some water-based ink in a distillation flask with anti-bumping granules, which help it boil smoothly. Fit a bung carrying a thermometer and a delivery tube. Lead the delivery tube to a receiving test tube cooled in ice, leaving its outlet open rather than sealing the apparatus. Support the flask above a Bunsen burner on a tripod and gauze. Heat gently until the ink boils. Water vapour travels along the delivery tube, cools and condenses to liquid water in the receiver. The dyes do not travel over with the water vapour, so they remain in the flask. Record the temperature during steady boiling and observe the appearance of the collected liquid and the residue. A colourless distillate is consistent with water having been separated from coloured ink, although appearance by itself does not prove purity.
Wear eye protection, keep hair and loose clothing clear of the flame, and let hot glassware cool before touching it. Water is a suitable chromatography solvent only if the ink's dyes dissolve in it; some inks need a different solvent. If that solvent is flammable, keep it well away from the Bunsen burner and follow the precautions for its vapour and skin contact. The two parts can be carried out separately so that chromatography solvent is not exposed to the flame.
Investigate both parts of ink: use paper chromatography to separate its dyes and simple distillation to separate pure water from suitable water-based ink.
Spot ink on a pencil start line above the solvent. Let the solvent rise through the paper; remove it before the front reaches the top and mark the solvent front immediately. Separate spots indicate different dyes. Compare samples under the same conditions.
Heat the ink gently with a Bunsen burner. Water evaporates, travels through a delivery tube and condenses in a cooled receiver; dyes stay in the flask. Record the boiling temperature and observations. Use eye protection, handle hot glassware carefully, and keep flammable solvents away from the flame.
Describe both parts of this core practical: chromatography separates the dyes in ink; simple distillation separates water from ink.
Use pencil for the starting line and keep it above the solvent level, or the samples may wash into the solvent.
Mark the solvent front as soon as the paper is removed, before the solvent evaporates.
Keep flammable solvents away from the Bunsen burner and allow hot apparatus to cool before handling it.
It can see this note and what your specification asks for.
Answers are free with an account.
1 free note left this week
Get more free notesYour answer sets when this note comes back for review, or marks it complete.
Was this note helpful?
Log in to tell us whether it helped, or to report a problem.
Last updated
Solvent
A liquid that dissolves another substance to form a solution.
Paper chromatography
A method of separating soluble substances as a solvent carries them through paper at different speeds.
Chromatogram
The paper showing the separated spots after chromatography.
Simple distillation
A method of separating a liquid from a mixture by boiling it and then condensing its vapour.
Distillate
The liquid collected after vapour has cooled and condensed during distillation.
Put your knowledge into practice — try past paper questions for Chemistry
Solvent
A liquid that dissolves another substance to form a solution.
Paper chromatography
A method of separating soluble substances as a solvent carries them through paper at different speeds.
Chromatogram
The paper showing the separated spots after chromatography.
Simple distillation
A method of separating a liquid from a mixture by boiling it and then condensing its vapour.
Distillate
The liquid collected after vapour has cooled and condensed during distillation.