GCSE›AQA GCSE Chemistry›Mind mapsPurity, Formulations and ChromatographyAQA GCSE Chemistry: Mind mapStudy pack PDFAlso for this subtopic:Revision notesFlashcardsSubtopic testCover factsPure or mixture?Pure substance: one element or compound onlyMixture: two or more substances, not chemically bondedPure → fixed melting and boiling pointMixture → melts and boils over a rangeFormulationsMixture designed for a specific useMade in precise proportionsMedicines, fuels, alloys, cosmetics, fertilisersNot a compound: can be separated physicallyPaper chromatographyDraw the baseline in pencilSolvent rises by capillary actionMore soluble, less adsorbed → travels furtherEach spot is a different componentPurityand chromatographyRfRf valuesRf=distance moved by substancedistance moved by solvent\text{R}_f = \frac{\text{distance moved by substance}}{\text{distance moved by solvent}}Rf=distance moved by solventdistance moved by substanceMeasure from the baselineAlways between 0 and 1Same solvent as the standard to compareReading resultsOne spot = pureTwo or more spots = mixtureSame Rf as a standard = same substanceSpot darkness shows concentration, not identityExam tipsRange of melting points → different componentsNever use pen for the baselineExplain using solubility and adsorptionChanging solvent changes the Rf values