Two hot liquids, P and Q, are left to cool. Both are seen to turn completely solid during the 6 minutes.
| Time / min | 0 | 1 | 2 | 3 | 4 | 5 | 6 |
|---|---|---|---|---|---|---|---|
| P temperature / ∘C^\circ\mathrm{C}∘C | 90 | 84 | 79 | 79 | 79 | 79 | 72 |
| Q temperature / ∘C^\circ\mathrm{C}∘C | 90 | 85 | 81 | 78 | 76 | 74 | 70 |
Which conclusion is best supported by the data?
P is pure and Q is a mixture, because Q freezes over a range
Q is pure and P is a mixture, because the temperature of P stops falling
Both are pure, because both liquids turn completely into solids
Both are mixtures, because the temperature of both falls overall
107 exam-style questions on Edexcel GCSE Chemistry 3.2 Methods of separating and purifying substances, covering 3.2.1 Pure substances and mixtures, 3.2.2 Techniques for separating mixtures, 3.2.3 Paper chromatography and Rf values, and 3.2.4 Making water potable. Each one has a worked solution and a mark scheme showing where the marks go.