Lesson Plan

• Describe qualitative tests using aqueous NaOH and NH₃ to identify Al³⁺, NH₄⁺, Ca²⁺, Cr³⁺ and Cu²⁺ ions.
• Explain the precipitation and solubility behaviour of each ion in both reagents.
• Apply observed colour and solubility changes to correctly record ion identification.
• Compare the responses of transition‑metal cations with those of non‑metal cations.
• Evaluate safety procedures when handling NaOH and NH₃ in the laboratory.

• Dilute NaOH solution (~0.1 M) and additional NaOH for excess tests.
• Dilute NH₃ solution (~0.1 M) and additional NH₃ for excess tests.
• Test tubes, rack, pipettes and droppers.
• Sample solutions of Al³⁺, NH₄⁺, Ca²⁺, Cr³⁺, Cu²⁺.
• White tile or lab notebook for recording observations.
• Safety goggles, gloves, lab coat.
• Red and blue litmus paper.

Today we will explore how simple reagents can reveal the identity of hidden ions in solution. Building on your prior work with precipitation reactions, you will use NaOH and ammonia to differentiate five common cations. By the end of the lesson you will be able to predict and interpret the colour and solubility outcomes for each ion.

1. Do‑now (5'): Students list known precipitation reactions for NaOH and share one example.
2. Mini‑lecture (10'): Review solubility rules and introduce complex formation with excess NH₃.
3. Teacher demonstration (15'): Perform the NaOH and NH₃ tests for each of the five ions, modelling observation recording.
4. Guided practice (15'): Pairs conduct the tests on provided samples, fill the observation table, and discuss results.
5. Check for understanding (5'): Quick exit‑card quiz – match each ion with its solubility behaviour in excess NaOH.
6. Summary discussion (5'): Highlight patterns, reinforce safety reminders, and answer lingering questions.

To wrap up, we revisited the characteristic precipitates and their behaviour with excess reagents, confirming each ion’s identity. For your exit ticket, write the expected colour and solubility result for Cu²⁺ with ammonia. For homework, complete the worksheet that asks you to predict outcomes for two additional cations not covered today.