1(b) Elements, compounds and mixtures
Pearson Edexcel International GCSE Chemistry · 4CH1
Paper 2 | Whole paper: All content including bold C statements
Telling substances apart, and the separation techniques that exploit their differences.
Specification coverage
Topic 1 Principles of chemistry (b) Elements, compounds and mixtures — statements 1.5–1.13C (includes bold C statements assessed on Paper 2 only)
Assessment objectives: AO1, AO2, AO3. Suggested learning time: 60 minutes.
Required knowledge
- The definitions of element, compound and mixture
- Separation techniques: simple distillation, fractional distillation, filtration, crystallisation and paper chromatography
- How to choose a technique from the properties of the mixture
- Interpreting a chromatogram, including the use of a locating agent
- Bold C statements: the calculation and use of Rf values
Required skills
- Select and justify a separation technique for a given mixture
- Interpret a chromatogram and calculate Rf
- Describe apparatus accurately enough for a method to be followed
- Describe and evaluate the required practical: Investigate paper chromatography using inks or food colourings.
How it is examined
- Multiple-choice and short-answer recall
- Application of the content to an unfamiliar context
- Extended open-response, marked on the quality of a connected explanation
- Practical questions on method, variables, data and sources of error
Common mistakes
- Giving Rf a unit. It is a ratio of two lengths, so it has none.
- Drawing the chromatography baseline in ink, which then separates and ruins the result — it must be pencil.
- Starting the baseline below the solvent level, which washes the sample off the paper.