This memory aid covers Memory Aid 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 10 of 13 in this topic. Use it for quick recall, then test yourself straight afterwards so the memory aid becomes usable in an answer.
🧠 Memory Aid
PURE = one type of substance ONLY, SHARP melting point
To remember what impurities do to melting and boiling points:
"IMPURITIES: Melt LOW, Boil HIGH — they spread the range WIDE"
Think of salting icy roads (lowers freezing/melting point) and salting cooking water (raises boiling point) — both effects in one real-world example.
Quick Check: State TWO ways you could test whether a sample of an organic compound is pure.
1. Measure the melting point — if it melts sharply at the known literature value, it is likely pure. 2. Run paper or thin-layer chromatography — a single spot confirms a single compound (pure substance).
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.