GCSE Chemistry: Chemical Analysis

Chemical analysis is the detective work of GCSE Chemistry: deciding what a substance is, whether it is pure, and what a mixture contains. This quiz covers the full analytical toolkit the specification requires.

Purity opens the set with the definitional trap examiners set every year: in chemistry, a pure substance contains only one element or compound — quite different from the everyday sense in which "pure" orange juice is a mixture of many compounds. Formulations follow as the flip side: mixtures designed deliberately, with each component in a measured proportion for a purpose — tested twice through example-recognition questions spanning paints, medicines, alloys and fertilisers.

Chromatography forms the technical core. The quiz covers the two phases by name (mobile and stationary), the reason different substances travel different distances (their relative attraction to each phase), and the Rf calculation in both directions: computing 3 cm over 8 cm as 0.375, and inverting the formula to find how far a substance travelled given its Rf of 0.5 and a 10 cm solvent front. These two-way calculations mirror how the skill is actually assessed.

The gas tests complete the set as pure pattern-matching, exactly as the exam treats them: hydrogen's squeaky pop with a burning splint, oxygen relighting a glowing splint, carbon dioxide turning limewater milky, and chlorine bleaching damp litmus paper. A multi-select question combines several tests, checking that each pairing is secure rather than half-remembered.

Every question is self-contained with all measurement values provided, and the explanations restate the underlying principle, from phase affinity to why each gas test works.

• Define chemical purity and distinguish it from the everyday meaning
• Recognise formulations and explain why their compositions are fixed
• Explain how paper chromatography separates substances via the mobile and stationary phases
• Calculate and apply Rf values in both directions
• Recall the standard laboratory tests for hydrogen, oxygen, carbon dioxide and chlorine

Topic scope follows the Department for Education's GCSE chemistry subject content (shared in part with combined science), chemical analysis strand: purity, formulations, chromatography and identification tests for common gases.