| Lesson Plan |
| Grade: |
Date: 25/02/2026 |
| Subject: Chemistry |
| Lesson Topic: Describe the use of a flame test to identify the cations: (a) lithium, $mathrm{Li}^{+}$ (b) sodium, $mathrm{Na}^{+}$ (c) potassium, $mathrm{K}^{+}$ (d) calcium, $mathrm{Ca}^{2+}$ (e) barium, $mathrm{Ba}^{2+}$ (f) copper(II), $mathrm{Cu}^{2+}$ |
Learning Objective/s:
- Describe the principle of flame emission and its relation to electron transitions.
- Identify the characteristic flame colours of Li⁺, Na⁺, K⁺, Ca²⁺, Ba²⁺, and Cu²⁺ ions.
- Perform a flame test safely and accurately, recording observations.
- Compare observed colours with reference data to determine unknown cations.
- Evaluate common sources of error and suggest improvements.
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Materials Needed:
- Bunsen burner with non‑luminous flame
- Clean nichrome or platinum wire loops
- Dilute hydrochloric acid (for cleaning loops)
- Sample salts: LiCl, NaCl, KCl, CaCl₂, BaCl₂, CuSO₄
- Safety goggles, lab coat, gloves
- Flame‑colour reference chart or worksheet
- Waste disposal container
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Introduction:
Begin with a quick demonstration of a bright yellow flame, asking students what element might produce that colour. Recall prior knowledge of electron excitation and emission spectra as the basis for colour formation. Explain that by the end of the lesson they will be able to carry out a flame test and correctly identify six common cations.
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Lesson Structure:
- Do‑now (5'): Students label a flame‑colour chart from memory (checks prior knowledge).
- Mini‑lecture (10'): Explain electron transitions and colour‑emission principle; introduce the reference table.
- Demonstration (8'): Teacher performs a flame test on Na⁺ and discusses the observation.
- Guided lab activity (20'): Pairs conduct flame tests on the six cation samples, record colours, and compare with the chart; teacher circulates for safety and loop cleaning.
- Error‑analysis discussion (5'): Groups identify possible sources of error in their results and suggest improvements.
- Quick quiz (2'): Exit ticket – write the flame colour for each cation.
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Conclusion:
Summarise that each cation emits a unique colour due to specific electron transitions, reinforcing the link between spectra and identification. Collect the exit tickets to gauge understanding and clarify any lingering misconceptions. Assign homework: research another qualitative test for metal ions and prepare a short report.
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