| Lesson Plan |
| Grade: |
Date: 25/02/2026 |
| Subject: Chemistry |
| Lesson Topic: Describe tests to identify the gases: (a) ammonia, $mathrm{NH}_3$, using damp red litmus paper (b) carbon dioxide, $mathrm{CO}_2$, using limewater (c) chlorine, $mathrm{Cl}_2$, using damp litmus paper (d) hydrogen, $mathrm{H}_2$, using a lighted spli |
Learning Objective/s:
- Describe the characteristic observations for ammonia, carbon dioxide, chlorine, and hydrogen gas tests.
- Explain the chemical reactions that give rise to each qualitative observation.
- Demonstrate safe laboratory procedures when handling gases and reagents.
- Apply the tests to identify unknown gases in a practical activity.
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Materials Needed:
- Gas delivery tubes and rubber tubing
- Test tubes (clean, dry)
- Limewater (saturated Ca(OH)₂ solution)
- Damp red and blue litmus paper
- Distilled water (for moistening litmus)
- Wooden splints and Bunsen burner
- Safety goggles, gloves, lab coats
- Worksheet/record sheet for observations
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Introduction:
Begin with a short “mystery gas” video to spark curiosity. Ask students what they already know about how acids, bases and combustion can be detected in the lab. State that by the end of the lesson they will be able to correctly perform and interpret four standard gas‑identification tests.
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Lesson Structure:
- Do‑now (5'): Match gas symbols to everyday uses on a worksheet – activates prior knowledge.
- Mini‑lecture (10'): Review the chemistry behind litmus colour change, limewater precipitation, and the pop test.
- Teacher demonstration (15'): Show each test (NH₃, CO₂, Cl₂, H₂) while students note observations on their sheets.
- Guided practice (15'): In pairs, students repeat two of the tests (e.g., NH₃ & CO₂) using the supplied apparatus, observing safety rules.
- Whole‑class discussion (10'): Groups share results; teacher clarifies misconceptions and reinforces safety precautions.
- Exit ticket (5'): Students write one key observation that confirms each gas.
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Conclusion:
Recap the four characteristic observations and link them back to the underlying reactions. Collect exit tickets to gauge understanding and assign a short homework task: students must write a paragraph describing how they would identify an unknown gas using two of the tests learned today.
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