O Levels/IGCSE Chemistry Lesson Plan 9.3

Section	Details
Objective	– Describe an alloy as a mixture of a metal with other elements.- Provide examples of alloys: (a) brass (copper and zinc), (b) stainless steel (iron with chromium, nickel, and carbon).
Activities	– Starter (5 mins): Show examples of brass and stainless steel objects (e.g., a brass ornament, stainless steel cutlery). Ask: “How are these materials different from pure metals?”- Main (25 mins): 1. Define an alloy and explain how it is made by mixing metals with other elements. 2. Discuss brass as a mixture of copper and zinc and its applications (e.g., musical instruments, decorative items). 3. Discuss stainless steel as a mixture of iron, chromium, nickel, and carbon, emphasizing its resistance to rust and hardness. 4. Highlight other common alloys (e.g., bronze, duralumin).- Plenary (10 mins): Students complete a table summarizing the composition and uses of common alloys.
Resources	Samples of alloys (brass, stainless steel), worksheets, periodic table.
Time	40 minutes total: 5 mins (Starter) + 25 mins (Main) + 10 mins (Plenary).
Homework	Research and write about one alloy not covered in class, describing its composition and uses.
Assessment	Worksheet: Match given alloys to their compositions and common uses.
Past Paper Practice	IGCSE Chemistry 0620/41/M/J/20 Q6(b) – Descriptions and examples of alloys.

Section	Details
Objective	Explain in terms of structure how alloys are harder and stronger than pure metals, due to different sized atoms or ions preventing layers from sliding over each other.
Activities	– Starter (5 mins): Ask: “Why do you think alloys are often stronger than pure metals?”- Main (25 mins): 1. Explain the structure of pure metals (layers of identical atoms that can slide over each other, making them soft). 2. Describe how adding different-sized atoms in alloys disrupts the layers, making sliding difficult and increasing hardness and strength. 3. Show diagrams of pure metals and alloys to illustrate the difference. 4. Relate the structure to real-world applications (e.g., stainless steel for cutlery and construction).- Plenary (10 mins): Students label diagrams of pure metal and alloy structures and explain why alloys are harder.
Resources	Structural diagrams of pure metals and alloys, worksheets, videos.
Time	40 minutes total: 5 mins (Starter) + 25 mins (Main) + 10 mins (Plenary).
Homework	Write a short explanation of how the structure of alloys makes them harder than pure metals, with a diagram.
Assessment	Worksheet: Compare the structures of pure metals and alloys, explaining the difference in hardness.
Past Paper Practice	IGCSE Chemistry 0620/41/O/N/21 Q6(a) – Structural explanation of alloy strength.

Section	Details
Objective	Describe the uses of alloys in terms of their physical properties, including stainless steel in cutlery because of its hardness and resistance to rusting.
Activities	– Starter (5 mins): Show stainless steel cutlery and ask: “Why is stainless steel preferred for making cutlery?”- Main (25 mins): 1. Discuss the hardness and resistance to rusting of stainless steel, linking these properties to its structure and composition. 2. Provide examples of alloy uses: – Brass in decorative items and musical instruments. – Bronze in statues and medals. – Duralumin in aircraft manufacturing. 3. Highlight the economic and practical advantages of using alloys over pure metals.- Plenary (10 mins): Students match different alloys to their uses based on their properties in a worksheet.
Resources	Samples or images of alloy applications, worksheets, comparison charts.
Time	40 minutes total: 5 mins (Starter) + 25 mins (Main) + 10 mins (Plenary).
Homework	Write a short report on why stainless steel is used in kitchens and construction.
Assessment	Worksheet: Identify alloys based on their uses and physical properties.
Past Paper Practice	IGCSE Chemistry 0620/41/M/J/19 Q6(d) – Applications of alloys based on their properties.

Section	Details
Objective	Identify representations of alloys from diagrams of structure.
Activities	– Starter (5 mins): Show diagrams of pure metals and alloys and ask: “Which one represents an alloy? Why?”- Main (25 mins): 1. Recap the structure of alloys and how different-sized atoms disrupt layers. 2. Provide multiple structural diagrams and guide students in identifying pure metals and alloys. 3. Discuss how the structural differences lead to variations in properties like hardness and strength.- Plenary (10 mins): Students complete a worksheet labeling diagrams as pure metals or alloys and explaining their reasoning.
Resources	Structural diagrams, worksheets, periodic table.
Time	40 minutes total: 5 mins (Starter) + 25 mins (Main) + 10 mins (Plenary).
Homework	Draw labeled diagrams of pure metal and alloy structures, highlighting the differences.
Assessment	Worksheet: Identify and explain the structural differences between pure metals and alloys.
Past Paper Practice	IGCSE Chemistry 0620/41/O/N/20 Q5(c) – Identifying alloys from structural diagrams.

Definition:
- Alloys are mixtures of metals with other elements.
- Examples: Brass (copper + zinc), stainless steel (iron + chromium, nickel, carbon).
Structure and Properties:
- Alloys are harder and stronger than pure metals due to disrupted atomic layers.
- This prevents layers from sliding over each other easily.
Uses of Alloys:
- Brass: Musical instruments, decorative items (aesthetic and durable).
- Stainless steel: Cutlery, construction (resistant to rust and hard).
- Duralumin: Aircraft manufacturing (lightweight and strong).

Provide hands-on examples (if possible) of alloys to illustrate their properties.
Use diagrams to explain the structural differences between pure metals and alloys.
Relate the properties of alloys to their applications in real life for better understanding.