The unit in one line
How you find out what a substance is, how you get it clean, and how you measure how much of it there is. 3 of Chemistry's 50 questions over three chapters, and the one unit that pays back everything learnt elsewhere.
Read in this order
- Chemical tests (11 min) — the basic radicals group by group with their confirmatory colours, the acid radicals, flame colours, the functional-group tests, Lassaigne's sodium fusion and the biomolecule tests.
- Separation techniques (9 min) — crystallisation, the three distillations, paper chromatography with its Rf, and atmolysis.
- Types of titration (10 min) — the four acid-base curves and their indicators, permanganometry, iodometry against iodimetry, and the EDTA titration.
About 30 minutes in all. Chapter 3 sits directly on Volumetric analysis and Ionic equilibrium; read those first and this one becomes revision.
How it is asked
MEC sets the paper roughly half recall, a third understanding and a fifth application. Recall is a colour or a reagent: what group reagent, what precipitate, what indicator. Understanding is why the boiling with nitric acid before adding silver nitrate is compulsory, or why starch goes in late in an iodometric titration. Application is a described observation worked back to an answer, or a titre turned into a purity.
Then practise
Each chapter has a fixed-length chapter test under Practice › Topics, drawn from questions written to that chapter's scope. Sit it after reading; a second sitting a week later shows whether it stuck.