Topic: Acids, Bases, and Salts – Preparation of Salts
Lesson 1: Preparation of Soluble Salts
| Section | Details |
|---|---|
| Objective | Describe the preparation, separation, and purification of soluble salts by reacting acids with: (a) alkalis by titration, (b) excess metal, (c) excess insoluble base, (d) excess insoluble carbonate. |
| Activities | – Starter (5 mins): Show examples of common salts (e.g., NaCl, CuSO₄) and ask: “How are these salts prepared?”- Main (25 mins): 1. Demonstrate titration for preparing sodium chloride from NaOH and HCl. 2. Explain the use of excess reactants for preparing salts (e.g., Zn + H₂SO₄ → ZnSO₄ + H₂ or CuO + H₂SO₄ → CuSO₄ + H₂O). 3. Discuss methods for separating and purifying the salts (e.g., filtration, evaporation, crystallization). 4. Conduct a practical (e.g., preparing CuSO₄ from CuO and H₂SO₄).- Plenary (10 mins): Students write step-by-step instructions for preparing a soluble salt of their choice. |
| Resources | Acids, alkalis, metals, insoluble bases, carbonates, burette, pipette, beakers, worksheets. |
| Time | 40 minutes total: 5 mins (Starter) + 25 mins (Main) + 10 mins (Plenary). |
| Homework | Write balanced equations for the preparation of CuSO4\text{CuSO}_4 and NaCl\text{NaCl} using the methods taught. |
| Assessment | Worksheet: Identify the method for preparing given salts and write balanced equations. |
| Past Paper Practice | IGCSE Chemistry 0620/41/M/J/20 Q2(b) – Methods of preparing salts from acids. |
Lesson 2: Preparation of Insoluble Salts by Precipitation
| Section | Details |
|---|---|
| Objective | Describe the preparation of insoluble salts by precipitation. |
| Activities | – Starter (5 mins): Show an insoluble salt (e.g., BaSO₄) and ask: “How do we prepare this salt?”- Main (25 mins): 1. Define precipitation reactions and provide examples (e.g., BaCl₂ + H₂SO₄ → BaSO₄ + 2HCl). 2. Demonstrate the preparation of an insoluble salt (e.g., mixing lead(II) nitrate and potassium iodide to form PbI₂). 3. Discuss the steps for filtering, washing, and drying the precipitate.- Plenary (10 mins): Students summarize the process of preparing insoluble salts in a flowchart. |
| Resources | Solutions for precipitation reactions (e.g., Pb(NO₃)₂, KI), beakers, filter paper, worksheets. |
| Time | 40 minutes total: 5 mins (Starter) + 25 mins (Main) + 10 mins (Plenary). |
| Homework | Write equations for two precipitation reactions and explain the steps to isolate the salt. |
| Assessment | Worksheet: Match reactants to the insoluble salts they form and write equations. |
| Past Paper Practice | IGCSE Chemistry 0620/41/O/N/21 Q3(c) – Precipitation reactions for preparing salts. |
Lesson 3: General Solubility Rules
| Section | Details |
|---|---|
| Objective | Describe the general solubility rules for salts, including exceptions. |
| Activities | – Starter (5 mins): Ask: “Why do some salts dissolve in water while others don’t?”- Main (25 mins): 1. Explain solubility rules with examples: – Sodium, potassium, ammonium salts are soluble. – Nitrates are soluble. – Chlorides are soluble, except lead and silver. – Sulfates are soluble, except barium, calcium, and lead. – Carbonates are insoluble, except sodium, potassium, and ammonium. – Hydroxides are insoluble, except sodium, potassium, ammonium, and calcium (partially). 2. Provide practice classifying salts based on solubility rules.- Plenary (10 mins): Students complete a table summarizing solubility rules. |
| Resources | Solubility rule chart, examples of salts, worksheets. |
| Time | 40 minutes total: 5 mins (Starter) + 25 mins (Main) + 10 mins (Plenary). |
| Homework | Write a list of soluble and insoluble salts based on solubility rules. |
| Assessment | Quiz: Identify whether given salts are soluble or insoluble and justify. |
| Past Paper Practice | IGCSE Chemistry 0620/41/M/J/19 Q2(d) – Solubility rules and their applications. |
Lesson 4: Hydrated and Anhydrous Substances
| Section | Details |
|---|---|
| Objective | Define a hydrated substance as containing water and an anhydrous substance as containing no water. Define water of crystallisation with examples (e.g., CuSO₄·5H₂O, CoCl₂·6H₂O). |
| Activities | – Starter (5 mins): Show hydrated copper(II) sulfate crystals and anhydrous copper(II) sulfate. Ask: “What makes them different?”- Main (25 mins): 1. Define hydrated and anhydrous substances with examples. 2. Explain water of crystallisation and its role in hydrated salts. 3. Demonstrate the heating of CuSO4⋅5H2O\text{CuSO}_4·5\text{H}_2\text{O} to form anhydrous CuSO4\text{CuSO}_4. 4. Discuss the reversible reaction with water addition.- Plenary (10 mins): Students write definitions and examples of hydrated and anhydrous substances. |
| Resources | Hydrated and anhydrous salts, Bunsen burner, worksheets. |
| Time | 40 minutes total: 5 mins (Starter) + 25 mins (Main) + 10 mins (Plenary). |
| Homework | Write the reactions for the hydration and dehydration of copper(II) sulfate. |
| Assessment | Worksheet: Identify substances as hydrated or anhydrous and write equations for changes. |
| Past Paper Practice | IGCSE Chemistry 0620/41/O/N/20 Q2(e) – Hydrated and anhydrous substances with water of crystallisation. |
Notes for Teachers:
- Incorporate hands-on experiments wherever possible to engage students and clarify concepts.
- Emphasize the practical applications of solubility rules and the preparation of salts in real-world contexts.
- Reinforce the connections between theory (e.g., solubility rules) and observations (e.g., precipitation, crystallization).
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