Topic: Electrochemistry – Electrolysis
Lesson 1: Definition and Basic Components of Electrolysis
| Section | Details |
|---|---|
| Objective | Define electrolysis as the decomposition of an ionic compound when molten or in aqueous solution, by the passage of an electric current. Identify the anode, cathode, and electrolyte in simple electrolytic cells. |
| Activities | – Starter (5 mins): Ask: “What happens when electricity passes through water?” Discuss decomposition. – Main (25 mins): 1. Define electrolysis. 2. Introduce the key components: anode (positive electrode), cathode (negative electrode), and electrolyte (molten or aqueous ionic compound). 3. Demonstrate a simple electrolysis setup and label the components. – Plenary (10 mins): Students label diagrams of electrolytic cells and describe the roles of each component. |
| Resources | Electrolysis apparatus, diagrams, worksheets with cell labeling exercises. |
| Time | 40 minutes total: 5 mins (Starter) + 25 mins (Main) + 10 mins (Plenary). |
| Homework | Write definitions of electrolysis, anode, cathode, and electrolyte, including diagrams. |
| Assessment | Worksheet: Identify and label the anode, cathode, and electrolyte in diagrams of electrolytic cells. |
| Past Paper Practice | IGCSE Chemistry 0620/41/M/J/20 Q7(a) – Basic electrolysis and components. |
Lesson 2: Transfer of Charge During Electrolysis
| Section | Details |
|---|---|
| Objective | Describe the transfer of charge during electrolysis, including: (a) movement of electrons in the external circuit, (b) loss/gain of electrons at electrodes, (c) movement of ions in the electrolyte. |
| Activities | – Starter (5 mins): Recap the role of electrodes and electrolyte. – Main (25 mins): 1. Explain electron flow in the external circuit (from anode to cathode). 2. Discuss oxidation (loss of electrons at the anode) and reduction (gain of electrons at the cathode). 3. Explain the movement of cations (to cathode) and anions (to anode) in the electrolyte. – Plenary (10 mins): Students summarize the processes at electrodes and in the electrolyte using diagrams. |
| Resources | Diagrams, animations/videos, worksheets for practice questions. |
| Time | 40 minutes total: 5 mins (Starter) + 25 mins (Main) + 10 mins (Plenary). |
| Homework | Write half-equations for the transfer of charge in molten NaCl. |
| Assessment | Quiz: Describe the transfer of charge during electrolysis for a given setup. |
| Past Paper Practice | IGCSE Chemistry 0620/41/O/N/21 Q7(b) – Charge transfer during electrolysis. |
Lesson 3: Products and Observations During Electrolysis
| Section | Details |
|---|---|
| Objective | Identify the products formed at the electrodes and describe observations during the electrolysis of: (a) molten lead(II) bromide, (b) concentrated aqueous sodium chloride, (c) dilute sulfuric acid using inert electrodes. |
| Activities | – Starter (5 mins): Discuss what ions are present in molten PbBr₂, NaCl(aq), and H₂SO₄(aq). – Main (25 mins): 1. Explain how the ions determine products at each electrode. 2. Identify products and observations for each electrolyte. 3. Demonstrate one of the electrolysis setups and describe the results. – Plenary (10 mins): Students complete a table summarizing products and observations for each setup. |
| Resources | Electrolysis setups for PbBr₂, NaCl, and H₂SO₄, observation sheets, diagrams. |
| Time | 40 minutes total: 5 mins (Starter) + 25 mins (Main) + 10 mins (Plenary). |
| Homework | Write half-equations for the electrolysis of PbBr₂, NaCl, and H₂SO₄. |
| Assessment | Worksheet: Predict products and describe observations for given electrolytes. |
| Past Paper Practice | IGCSE Chemistry 0620/41/M/J/19 Q7(a) – Electrolysis products and observations. |
Lesson 4: Electrolysis of Copper(II) Sulfate with Different Electrodes
| Section | Details |
|---|---|
| Objective | Identify products and describe observations during the electrolysis of aqueous CuSO₄ using: (a) inert electrodes, (b) copper electrodes. |
| Activities | – Starter (5 mins): Recap the ions present in CuSO₄ solution and ask: “What determines the products at each electrode?” – Main (25 mins): 1. Explain reactions with inert electrodes (oxygen at anode, copper at cathode). 2. Explain reactions with copper electrodes (copper dissolves at anode, deposits at cathode). 3. Demonstrate both setups and describe the results.- Plenary (10 mins): Students compare the two setups using a Venn diagram. |
| Resources | Electrolysis setups, copper and graphite electrodes, worksheets for comparison. |
| Time | 40 minutes total: 5 mins (Starter) + 25 mins (Main) + 10 mins (Plenary). |
| Homework | Write a summary of the products formed with both electrode setups, including half-equations. |
| Assessment | Worksheet: Predict products for CuSO₄ electrolysis with both electrode types. |
| Past Paper Practice | IGCSE Chemistry 0620/41/O/N/20 Q7(c) – Electrolysis of CuSO₄ with inert and copper electrodes. |
Lesson 5: Predicting Products and Electroplating
| Section | Details |
|---|---|
| Objective | (a) Predict products at electrodes for the electrolysis of binary and halide compounds. (b) State that metal objects are electroplated to improve their appearance and resistance to corrosion and describe how metals are electroplated. |
| Activities | – Starter (5 mins): Show electroplated items (e.g., jewelry) and ask: “Why is electroplating important?” – Main (25 mins): 1. Explain the rules for predicting electrode products. 2. Describe the process of electroplating: object as cathode, plating metal as anode, and electrolyte containing plating metal ions. 3. Demonstrate a simple electroplating experiment. – Plenary (10 mins): Students write a diagram of an electroplating setup and label the components. |
| Resources | Electroplating apparatus, diagrams, observation sheets. |
| Time | 40 minutes total: 5 mins (Starter) + 25 mins (Main) + 10 mins (Plenary). |
| Homework | Research three uses of electroplating in everyday life and write about its advantages. |
| Assessment | Worksheet: Predict electrode products and describe electroplating. |
| Past Paper Practice | IGCSE Chemistry 0620/41/M/J/21 Q7(d) – Predicting products and explaining electroplating. |
Notes for Teachers:
- Use practical demonstrations to engage students and reinforce abstract concepts.
- Emphasize writing and balancing half-equations for electrode reactions.
- Relate the applications of electrolysis (e.g., electroplating) to real-world contexts.
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