Click each part to explore the chromatography setup and results
How Impurities Shift the Points
- Impurities lower the melting point
- Impurities raise the boiling point
- Melting/boiling occurs over a range rather than a fixed point
Quick Check: A sample of aspirin melts over the range 132–136 °C. Pure aspirin melts at 135 °C. What does this tell you?
The sample contains impurities. The depressed melting point and broad range both indicate the aspirin is not pure.
This diagram covers Paper Chromatography — Interactive Diagram within Purity & Formulations for GCSE Chemistry. Revise Purity & Formulations in Chemical Analysis for GCSE Chemistry with 22 exam-style questions and 12 flashcards. Use this page as part of a wider topic revision path rather than treating it as an isolated fact. It is section 4 of 13 in this topic. Focus on the labels, the relationships between parts, and the explanation that turns the diagram into an exam-ready answer.
Practice questions for Purity & Formulations
In chemistry, what does it mean for a substance to be described as 'pure'?
Explain why the presence of impurities in a substance lowers its melting point and causes it to melt over a range of temperatures.