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Chemical analysis - (CCEA) Choosing a method of separation

Most elements are rarely found in their pure form. They are found chemically combined with other elements in compounds. Compounds are often found mixed with other compounds. Mixtures may be separated and analysed.

Part of Combined ScienceStructures, trends, chemical reactions, quantitative chemistry and analysis

Choosing a method of separation

You鈥檒l have to choose the best separation technique when you鈥檙e asked to separate the components of a mixture. This table can help:

MixtureSeparating techniqueExample
Insoluble solid and liquidFiltrationSand and water
Soluble solid and liquid (solution)Crystalisation (by evaporation)Salt water (sodium chloride solution)
Two miscible liquidsDistillationEthanol and water
Soluble solids dissolved in a solventPaper chromatographyFood colourings, dyes and inks
MixtureInsoluble solid and liquid
Separating techniqueFiltration
ExampleSand and water
MixtureSoluble solid and liquid (solution)
Separating techniqueCrystalisation (by evaporation)
ExampleSalt water (sodium chloride solution)
MixtureTwo miscible liquids
Separating techniqueDistillation
ExampleEthanol and water
MixtureSoluble solids dissolved in a solvent
Separating techniquePaper chromatography
ExampleFood colourings, dyes and inks