Purification and Chromatography Techniques — OCR GCSE Combined Science B J260
OCR GCSE Combined Science B · J260
Purification and Chromatography Techniques
What you need to know
Explain that many highly useful commercial materials are carefully constructed formulations of chemical mixtures.
Explain the concept of chemical purity, clearly distinguishing between the strict scientific definition of 'pure' and its general everyday usage.
Utilize melting point analysis data to differentiate between pure and impure chemical substances.
Recall that the process of chromatography involves both a stationary phase and a mobile phase, and explain that molecular separation is dependent on the specific distribution between these phases.
Interpret visual chromatograms, including the accurate calculation of Rf (retention factor) values.
Suggest appropriate chromatographic methods to distinguish pure substances from impure ones, detailing the specific use of paper chromatography, aqueous versus non-aqueous solvents, and locating agents.
Describe, explain, and provide concrete examples of the physical separation processes of filtration, crystallisation, simple distillation, and fractional distillation.
Suggest the most suitable purification technique when provided with specific information about the physical and chemical properties of the substances involved.
