| Lesson Plan |
| Grade: |
Date: 25/02/2026 |
| Subject: Biology |
| Lesson Topic: describe and carry out a semi-quantitative Benedict’s test on a reducing sugar solution by standardising the test and using the results (time to first colour change or comparison to colour standards) to estimate the concentration |
Learning Objective/s:
- Describe the chemical principle of Benedict’s test and the associated colour changes.
- Explain how to standardise the test using a series of glucose standards.
- Perform the semi‑quantitative Benedict’s test on an unknown sample, recording time to first colour change and final colour.
- Interpret results using the colour chart and the time‑concentration relationship to estimate sugar concentration.
- Evaluate sources of error and apply safety procedures during the experiment.
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Materials Needed:
- Projector and screen for diagram/flowchart
- Worksheet/data table for students
- Benedict’s solution (freshly prepared)
- Glucose standards (0.10 %–0.50 % w/v)
- Test tubes, 1 mL & 5 mL pipettes
- Water bath set to 95 °C
- Timer or stopwatch
- Colour comparison chart
- Lab safety gear (gloves, goggles, coat)
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Introduction:
Begin with a quick demonstration of a blue Benedict’s solution turning orange when heated with glucose, sparking curiosity about how colour reflects sugar amount. Recall students’ prior learning of redox reactions and how reducing sugars donate electrons. Today they will standardise the test, record the time to first colour change, and use the data to estimate an unknown sugar concentration.
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Lesson Structure:
- Do‑now (5'): Answer a short question on redox basics to activate prior knowledge.
- Mini‑lecture (10'): Explain the principle of Benedict’s test and introduce the colour chart.
- Standard preparation (10'): Weigh and dissolve glucose to make the five standard solutions.
- Standardisation activity (15'): Add Benedict’s reagent to each standard, heat, record time to first colour change and final colour, then plot a calibration curve.
- Testing the unknown (10'): Perform the test on the unknown sample, record observations, and estimate concentration using the chart and/or calibration line.
- Check for understanding (5'): Discuss sources of error, answer two extension questions, and clarify any misconceptions.
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Conclusion:
Summarise how the time to first colour change together with the final colour provides a semi‑quantitative estimate of sugar concentration. For the exit ticket, each student writes the estimated concentration of the unknown on a sticky note and hands it in. Homework: complete the worksheet on calculating concentration using the linear equation and answer two of the extension questions.
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