O-Level and SEC G3 Chemistry K324
C1: Experimental Chemistry
Choose apparatus and separation methods, record observations precisely, and plan fair, safe measurements.
Reviewed for the 2027 cohort on 19 July 2026. The official syllabus remains authoritative for assessable wording and paper details.
Core notes
Experimental Chemistry is about choosing a method from the properties and evidence given. A strong answer names suitable apparatus, explains why each step works, records measurements with appropriate precision, and uses observations or physical data to judge identity and purity.
Apparatus, gas handling and measurement
Match apparatus to the quantity and precision required. Use a balance for mass, a thermometer for temperature, and a stopwatch for time. A measuring cylinder gives an approximate liquid volume, while a pipette delivers a fixed accurate volume and a burette delivers a measured variable volume. A gas syringe measures gas volume directly.
Choose gas collection from solubility and density. Collect a gas over water only if it is not very soluble or reactive with water. Upward or downward delivery depends on density relative to air. Drying agents must not react with the gas: K324 limits the named agents to calcium oxide, concentrated sulfuric acid, and fused calcium chloride.
Separation and purification
Choose a separation method from solubility, miscibility, boiling point, and whether a substance sublimes. Filtration separates an insoluble solid from a liquid. Crystallisation recovers a dissolved solid without heating it to dryness. Simple distillation recovers a solvent or separates liquids with well-separated boiling points, while fractional distillation handles miscible liquids with closer boiling points.
A separating funnel divides immiscible liquid layers after they settle. Sublimation separates a subliming solid from a non-subliming solid. A suitable solvent can dissolve one solid selectively before filtration and recovery. State what is retained at each step and whether the desired substance is the residue, filtrate, distillate, or crystals.
Chromatography, identity and purity
In paper chromatography, place a small concentrated spot above the solvent level. The solvent carries components at different relative rates. Compare spot positions with known samples, and calculate Rf as distance travelled by the substance divided by distance travelled by the solvent front. A locating agent is needed when separated components are colourless.
A pure substance has a sharp melting point or boiling point close to its accepted value. An impurity usually broadens and changes the melting range. Purity matters because an unknown component can alter dose, taste, reaction behaviour, or safety in food and drugs. Use the data supplied rather than claiming that appearance alone proves purity.
Formulae and relationships
| Relationship | Use |
|---|---|
| Compare a chromatogram component under the stated conditions. |
Worked examples
Example 1: A dye spot moves while the solvent front moves . Find its value and state one condition needed for a fair comparison with a known dye.
- Use distances measured from the same starting line.
- Calculate Rf as 4.2 divided by 6.0.
- Compare only chromatograms run with the same solvent and experimental conditions.
Answer: ; use the same solvent under comparable conditions.
Chapter checkpoint
Use these three moves to organise the topic before attempting a mixed or practical question.
- Choose apparatus from the required range, precision, heating, and containment needs.
- Select filtration, crystallisation, distillation, or chromatography from the mixture and desired product.
- Record observations separately from inferences and include safety, controls, repeats, and data treatment in plans.
Official outcome coverage
K324 C1: 6 mapped outcomes, references C1(a), C1(b), C1(c), C1(d), C1(e), C1(f). Check the official K324 syllabus.
The outcome wording is not reproduced here. The relevant official syllabus remains authoritative for exact assessable scope.
Practical and data connection
Treat every procedure as an argument: the apparatus, variable control, observation table, and safety step should each support the stated aim.
Exam traps and retrieval check
Avoid these traps
- Placing the sample spot below the solvent level so it dissolves into the reservoir.
- Heating a soluble salt solution to complete dryness when crystallisation is required.
- Choosing gas collection or a drying agent without checking whether the gas reacts or dissolves.
Check from memory
Why is a burette different from a pipette?
A burette measures a variable delivered volume, while a pipette delivers one fixed accurate volume.
What separates two immiscible liquids?
A separating funnel after the layers have settled.
Why use a locating agent?
To make colourless separated components visible.
Pure versus Combined scope
Combined Chemistry uses the same top-level topic label but a narrower outcome set. Use the Combined component checklist before removing or adding detail.
Shared explanation source
Eclat has a related explanation in its existing IP library. It can help with the shared concept, but its IP extensions and school-sensitive scope are not automatically part of K324. Open the related IP explanation.