Processing of Materials – Methods: Alloys

Subject: Basic Technology

Class: JSS 3

Term: First Term

Week: 5

Age: 12-15 years

Topic: Processing of Materials – Methods

Sub-topic: Alloys – Definition, Types, Properties, and Uses

Duration: 60 minutes

Behavioural Objectives

By the end of the lesson, students should be able to:

1. Define alloys and explain their purpose.
2. Identify different types of alloys.
3. Describe the properties of alloys.
4. List and explain common uses of alloys in daily life.

Keywords

• Alloy
• Ferrous
• Non-ferrous
• Corrosion
• Ductility

Set Induction

Begin the lesson by displaying metal objects like stainless steel spoons, coins, and brass door handles. Ask students to guess why these metals might be used in place of pure iron or copper.

Entry Behaviour

Students already know about metals from earlier classes and are familiar with some properties of metals such as strength and conductivity.

Learning Resources and Materials

• Samples of alloyed metals (e.g., stainless steel, brass, bronze)
• Videos on the process of making alloys
• Diagrams showing different types of alloys

Building Background/Connection to Prior Knowledge

Remind students of the basic properties of metals, such as malleability, conductivity, and rusting, to establish a link with the purpose of creating alloys.

Embedded Core Skills

• Critical thinking and problem-solving
• Observation and inquiry skills
• Application of knowledge to real-life situations

Learning Materials

• Sample alloys (coins, jewelry, door handles)
• Visual aids like infographics explaining alloy-making
• Handouts on types and uses of alloys

Reference Books

• Lagos State Scheme of Work
• Basic Technology for Junior Secondary Schools
• Metallurgy and Material Science Texts

Instructional Materials

• Printed diagrams of alloy structures
• Metal samples to compare pure and alloyed materials

Content

I. Definition of Alloys

An alloy is a combination of two or more elements, where at least one is a metal, to create a new material with enhanced properties. Alloys are designed to improve the strength, durability, and resistance of metals to corrosion.

II. Types of Alloys

1. Ferrous Alloys (Contain Iron)
   • Examples: Stainless steel, cast iron, carbon steel
   • Properties: Strong, durable, may rust unless treated
2. Non-Ferrous Alloys (Do Not Contain Iron)
   • Examples: Brass, bronze, aluminum alloy
   • Properties: Lightweight, resistant to rust, good conductors of electricity

III. Properties of Alloys

• Increased Strength: Alloys are stronger than pure metals.
• Corrosion Resistance: Alloys like stainless steel do not rust easily.
• Malleability and Ductility: Alloys can be shaped or drawn into wires without breaking.
• Better Conductivity: Some alloys, like brass, have good electrical conductivity.
• Improved Aesthetic Appeal: Alloys such as gold-plated or silver-plated metals are used in jewelry for beauty and durability.

IV. Uses of Alloys

1. Construction:
   • Stainless steel is used for bridges, buildings, and kitchen utensils.
2. Electrical Applications:
   • Brass and aluminum alloys are used in electrical wiring and fittings.
3. Transportation:
   • Aluminum alloys are used in aircraft and car manufacturing due to their lightweight nature.
4. Medical Equipment:
   • Titanium alloys are used in surgical tools and implants because they are biocompatible.
5. Jewelry and Coins:
   • Gold and silver alloys improve hardness and reduce wear in jewelry and coins.

Evaluation (Fill-in-the-Blank Questions)

1. An alloy is a __________ of two or more elements. (a) mixture (b) chemical (c) compound (d) metal
2. Brass is an example of a __________ alloy. (a) ferrous (b) non-ferrous (c) steel (d) carbon
3. __________ steel is resistant to rust. (a) Stainless (b) Mild (c) Carbon (d) Cast
4. An alloy of copper and tin is called __________. (a) brass (b) bronze (c) aluminum (d) iron
5. __________ is a property that allows a material to be drawn into wires. (a) Ductility (b) Malleability (c) Hardness (d) Conductivity
6. __________ alloys are used in airplane manufacturing. (a) Gold (b) Aluminum (c) Steel (d) Cast iron
7. __________ is a ferrous alloy. (a) Brass (b) Carbon steel (c) Bronze (d) Aluminum alloy
8. Alloys are used to prevent __________ in metals. (a) rust (b) weight (c) color change (d) shrinking
9. Coins are made using __________ alloys. (a) brass (b) bronze (c) silver (d) gold-plated
10. Titanium alloys are used in __________. (a) cooking tools (b) surgical implants (c) electric wiring (d) automobiles
11. Bronze is an alloy of __________ and tin. (a) copper (b) steel (c) gold (d) iron
12. __________ alloys do not contain iron. (a) Ferrous (b) Non-ferrous (c) Stainless (d) Carbon
13. __________ is an example of a lightweight alloy. (a) Brass (b) Cast iron (c) Aluminum alloy (d) Steel
14. Electrical wires are often made from __________ alloys. (a) aluminum (b) titanium (c) steel (d) gold
15. Alloys are used in medical tools because they are __________. (a) malleable (b) biocompatible (c) conductive (d) rust-prone

Class Activity Discussion (FAQs)

1. What is an alloy?
   An alloy is a combination of metals or a metal and another element to improve properties.
2. Why are alloys used instead of pure metals?
   Alloys are stronger, more durable, and more resistant to corrosion than pure metals.
3. What is the difference between ferrous and non-ferrous alloys?
   Ferrous alloys contain iron, while non-ferrous alloys do not.
4. What are some examples of ferrous alloys?
   Examples include carbon steel, cast iron, and stainless steel.
5. Why is aluminum alloy used in airplanes?
   Aluminum alloy is lightweight and strong, making it ideal for aircraft.
6. How does stainless steel resist rust?
   Stainless steel contains chromium, which forms a protective layer on the surface.
7. What is bronze used for?
   Bronze is used in statues, medals, and musical instruments.
8. Why is titanium alloy used in medical implants?
   Titanium is biocompatible, meaning it works well with human tissue.
9. What is the role of gold alloys in jewelry?
   Gold alloys improve hardness and reduce wear in jewelry.
10. What alloy is used in electrical wiring?
    Brass and aluminum alloys are used in electrical fittings and wires.

Teacher’s Activities

1. Introduce the topic with metal samples to compare pure and alloyed materials.
2. Explain the types, properties, and uses of alloys with the aid of diagrams.
3. Lead a class discussion on real-life applications of alloys.

Learners’ Activities

1. Identify different alloy types from samples provided.
2. Discuss the properties of alloys based on class activities.
3. List everyday items made from alloys and explain their benefits.

Evaluation Questions

1. Define an alloy.
2. What are the two types of alloys?
3. List three examples of non-ferrous alloys.
4. Describe the properties of stainless steel.
5. Why is bronze used for statues?
6. Name an alloy used in aircraft.
7. What is ductility?
8. Explain the importance of corrosion resistance in alloys.
9. How are titanium alloys used in the medical field?
10. What is the main difference between ferrous and non-ferrous alloys?

Conclusion

The teacher will assess the students’ responses and provide feedback, clarifying any doubts about alloys, their properties, and uses.