Chemistry (Combined Science) · GCSE · AQA · AQA GCSE Combined Science: Trilogy (8464) — Chemistry — Higher · Specification point · 5.8.1.3 · Chemical analysis · Purity, formulations and chromatography
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5.8.1.3 Chromatography
| Content | Key opportunities for skills development |
|---|---|
Chromatography can be used to separate mixtures and can give information to help identify substances. Chromatography involves a stationary phase and a mobile phase. Separation depends on the distribution of substances between the phases. The ratio of the distance moved by a compound (centre of spot from origin) to the distance moved by the solvent can be expressed as its value: |
Different compounds have different values in different solvents, which can be used to help identify the compounds. The compounds in a mixture may separate into different spots depending on the solvent but a pure compound will produce a single spot in all solvents.
Students should be able to:
WS 2.2, 3.1, 2, 3 MS 1a Recognise and use expressions in decimal form. MS 1c Use ratios, fractions and percentages. MS 1d Make estimates of the results of simple calculations. |
| MS 2a |
Required practical activity 12: investigate how paper chromatography can be used to separate and tell the difference between coloured substances. Students should calculate values.
AT skills covered by this practical activity: chemistry AT 1 and 4.
This practical activity also provides opportunities to develop WS and MS. Details of all skills are given in Key opportunities for skills development (page 183).