| Lesson Plan |
| Grade: |
Date: 25/02/2026 |
| Subject: Chemistry |
| Lesson Topic: Describe the Group I alkali metals, lithium, sodium and potassium, as relatively soft metals with general trends down the group, limited to: (a) decreasing melting point (b) increasing density (c) increasing reactivity |
Learning Objective/s:
- Describe the physical properties (softness, melting point, density) of lithium, sodium and potassium.
- Explain why melting point decreases, density increases and reactivity increases down Group I.
- Interpret the comparative data table to compare the three metals.
- Predict the vigor of the reaction of each metal with water.
- Write and balance the reaction equation for an alkali metal reacting with water.
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Materials Needed:
- Projector and screen
- Periodic table poster
- Printed data‑table handout for Li, Na, K
- Worksheet with trend questions
- Video clip of alkali metal‑water reactions (safe demonstration)
- Clickers or paper exit‑ticket cards
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Introduction:
Begin with a short video showing a piece of metal being cut with a knife to highlight the softness of alkali metals. Ask students what they already know about Group I elements and why they might behave differently from other metals. Explain that by the end of the lesson they will be able to describe the key trends in melting point, density and reactivity for lithium, sodium and potassium.
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Lesson Structure:
- Do‑Now (5 min): Quick quiz on electron configurations of Li, Na, K.
- Direct Instruction (10 min): Present the three trends using the comparative data table and explain the underlying electronic reasons.
- Guided Practice (12 min): Students work in pairs to fill a worksheet that asks them to rank the metals for each property and justify their answers.
- Demonstration Video (8 min): Show safe water‑reaction clips; pause to discuss observed differences in vigor.
- Class Discussion (10 min): Use clickers to poll predictions for an unseen alkali metal (e.g., rubidium) based on the trends.
- Formative Check (5 min): Exit‑ticket – write one sentence summarising why reactivity increases down the group.
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Conclusion:
Recap the three main trends and the electronic explanations behind them. Collect exit‑tickets to gauge understanding and address any misconceptions. For homework, assign a short task to research the next alkali metal (rubidium) and predict its melting point, density and reactivity using the trends discussed.
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