Topic: Chemistry of the Environment – Water
Lesson 1: Chemical Tests for Water
| Section | Details |
|---|---|
| Objective | – Describe chemical tests for water using anhydrous cobalt(II) chloride and anhydrous copper(II) sulfate. – Describe how to test for the purity of water using melting and boiling points. |
| Activities | – Starter (5 mins): Show a sample of water and ask: “How can we confirm that this is water and if it’s pure?” – Main (25 mins): 1. Demonstrate the color change of anhydrous cobalt(II) chloride (blue to pink) in the presence of water. 2. Demonstrate the color change of anhydrous copper(II) sulfate (white to blue) when hydrated. 3. Explain purity testing based on water’s melting point (0°C) and boiling point (100°C at standard pressure). 4. Discuss why these methods are reliable for identifying and confirming pure water. – Plenary (10 mins): Students complete a table summarizing the chemical tests and the results for water. |
| Resources | Anhydrous cobalt(II) chloride, anhydrous copper(II) sulfate, water samples, thermometer, Bunsen burner. |
| Time | 40 minutes total: 5 mins (Starter) + 25 mins (Main) + 10 mins (Plenary). |
| Homework | Write a step-by-step procedure for testing a sample of liquid for water and its purity. |
| Assessment | Worksheet: Match tests to results and explain how they confirm the presence and purity of water. |
| Past Paper Practice | IGCSE Chemistry 0620/41/M/J/20 Q4(a) – Chemical tests for water. |
Lesson 2: Impurities in Water
| Section | Details |
|---|---|
| Objective | – Explain why distilled water is used in practical chemistry. – State substances found in natural water sources and classify them as beneficial or harmful. |
| Activities | – Starter (5 mins): Ask: “Why can’t we use tap water for chemical experiments?” – Main (25 mins): 1. Explain that distilled water contains fewer chemical impurities than tap water, making it suitable for accurate chemical reactions. 2. Discuss substances in natural water: – Beneficial: Dissolved oxygen (for aquatic life), some metal compounds (essential minerals). – Harmful: Toxic metal compounds, plastics (harm aquatic life), sewage (microbes causing disease), nitrates and phosphates (cause deoxygenation). 3. Highlight real-life impacts of water pollution on ecosystems and human health. – Plenary (10 mins): Students classify a list of water impurities as beneficial or harmful in a table. |
| Resources | Worksheets, diagrams of water sources, videos on water pollution. |
| Time | 40 minutes total: 5 mins (Starter) + 25 mins (Main) + 10 mins (Plenary). |
| Homework | Research and write about how nitrates and phosphates affect aquatic life. |
| Assessment | Worksheet: Identify and classify substances in water as beneficial or harmful. |
| Past Paper Practice | IGCSE Chemistry 0620/41/O/N/21 Q5(b) – Impurities in natural water and their effects. |
Lesson 3: Treatment of Domestic Water Supply
| Section | Details |
|---|---|
| Objective | Describe the treatment of the domestic water supply, including sedimentation, filtration, carbon treatment, and chlorination. |
| Activities | – Starter (5 mins): Ask: “How does tap water become safe for drinking?” – Main (25 mins): 1. Explain the steps in water treatment: – Sedimentation: Large solid particles settle at the bottom of tanks. – Filtration: Removes smaller solids using sand and gravel filters. – Carbon treatment: Removes odors and tastes. – Chlorination: Kills harmful microbes. 2. Show a diagram of a water treatment plant and explain each step. 3. Highlight the importance of clean water for health and safety. – Plenary (10 mins): Students draw and label a flowchart summarizing the steps in water treatment. |
| Resources | Diagrams of water treatment plants, worksheets, videos of water treatment processes. |
| Time | 40 minutes total: 5 mins (Starter) + 25 mins (Main) + 10 mins (Plenary). |
| Homework | Write a paragraph explaining why chlorination is a crucial step in water treatment. |
| Assessment | Worksheet: Label a diagram of the water treatment process and explain the purpose of each step. |
| Past Paper Practice | IGCSE Chemistry 0620/41/M/J/19 Q5(a) – Domestic water treatment processes. |
Key Notes for Students:
- Tests for Water:
- Anhydrous cobalt(II) chloride: Blue to pink in water.
- Anhydrous copper(II) sulfate: White to blue in water.
- Pure water melts at 0°C and boils at 100°C.
- Impurities in Natural Water:
- Beneficial: Dissolved oxygen (supports aquatic life), essential minerals.
- Harmful: Toxic metals, plastics, microbes, nitrates, and phosphates (cause water deoxygenation).
- Water Treatment:
- Sedimentation: Removes large solids.
- Filtration: Removes smaller particles.
- Carbon treatment: Removes odors and tastes.
- Chlorination: Kills harmful microbes.
Notes for Teachers:
- Use hands-on experiments to demonstrate water tests and treatment processes where possible.
- Incorporate discussions on environmental impacts and the importance of clean water.
- Provide real-life examples to connect concepts to daily life and global issues like water pollution.
Leave a Reply