1. Experiment Snapshot
| Feature | Details |
|---|
| Experiment | Melting Point Determination |
| Difficulty | ⭐⭐⭐ Practical exam standard |
| Exam Importance | ⭐⭐⭐⭐ Organic practicals are common Section A targets |
| Typical Marks | 5–15 marks |
2. Aim
To determine the melting point of a solid and assess its purity.
3. Quick Theory
A pure substance has a sharp melting point. Impurities lower the melting point and make the melting range broader.
Examiner Tip: Link the practical step to its purpose. This is where students gain easy explanation marks.
4. Apparatus and Chemicals
| Apparatus | Chemicals |
|---|
| Melting point tube/capillary tube, thermometer, oil bath or melting point apparatus. | Dry solid sample such as benzoic acid. |
Safety: Wear goggles. Take care with hot apparatus, organic liquids, bromine water, acids, alkalis and flammable substances.
5. Labelled Practical Diagram
6. Step-by-Step Procedure
- Dry the sample fully.
- Place a small amount into a capillary tube.
- Attach the tube to the thermometer or place in apparatus.
- Heat slowly near the expected melting point.
- Record the temperature when melting starts.
- Record the temperature when melting is complete.
7. Observations / Results
| Stage | Expected Observation |
|---|
| Pure sample | Sharp melting point over a narrow range. |
| Impure sample | Lower and broader melting range. |
| Fast heating | Gives inaccurate melting point range. |
8. Sources of Error and Improvements
| Source of Error | Improvement |
|---|
| Incorrect heating or poor timing. | Heat gently and follow the sequence carefully. |
| Product loss or contamination. | Use clean apparatus and correct collection/filtration technique. |
| Incorrect observation wording. | Use exact exam words such as colourless, precipitate, crystals, reflux, or melting range. |
9. Student Common Mistakes
- Heating too quickly.
- Using wet crystals.
- Packing too much sample into the tube.
- Recording only one temperature instead of a range.
- Not comparing the result with the known melting point.
10. Examiner Tips and Traps
Examiner Tip: Organic practicals often ask why a step is done, not just what was done.
Examiner Trap: Do not write vague observations like “changed colour” or “gas formed” without the exact result.
11. 🎮 Interactive Simulator
Try It Yourself
A pure sample usually has a melting point range that is:
Impurities usually make the melting point:
Result Window
Ready
Choose the correct actions to complete the practical.
Score: 0/0
12. Past Paper Style Questions
- State the aim of this experiment. [2]
- Describe the preparation method in correct order. [4]
- State one safety precaution. [2]
- State one observation and its conclusion. [3]
- State one common source of error and one improvement. [4]
13. Mark Scheme
Aim correct [2].
Method in correct order with key apparatus/chemicals [4].
Safety point suitable for chemicals/heating [2].
Observation and conclusion linked correctly [3].
Valid error and improvement [4].
14. Quick Revision Card
- Aim: To determine the melting point of a solid and assess its purity.
- Key theory: A pure substance has a sharp melting point. Impurities lower the melting point and make the melting range broader.
- Most common mistake: Heating too quickly.
- Exam rule: Use exact observations and state the purpose of key steps.
15. Mastery Checklist
- I can state the aim.
- I can name apparatus and chemicals.
- I can describe the method in order.
- I know the expected observation.
- I can explain the purpose of key steps.
- I can avoid common student mistakes.