You have a mixture of substances with different sized molecules. how could you separate them

You would have to use chromatography there are various types for example 

Thin layer chromatography were you use a stationary medium such as silicon gel on glass and a mobile medium such a solvent. since the molecules will have different solubility's they will travel in the stationary phase at different speeds and so some will travel further than others. then you would calculate the RF value which is the distance travelled by the molecules / distance travelled by the solvent. with thin layer chromatography you can scrape the molecules off after an they will be separated.

You could also use GLC which heats up molecules very gradually and since each molecule has a different boiling point they will be evaporated at different rates which you then can collect and identify using the time they take.

I hope that my explanation helps

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