IDENTIFICATION OF METALS II
Subject : BASIC TECHNOLOGY
Term : FIRST TERM
Week: Week 7
Class : JSS1
Previous lesson :
The pupils have previous knowledge of IDENTIFICATION OF METALS
Topic :
IDENTIFICATION OF METALS II
Behavioural objectives :
At the end of the lesson, pupils would have learnt
- different types of metals
- Definition and Properties of Metal
- Classes of Metal
- Processing of Metal
- Uses of Metal
Instructional Materials :
- Wall charts
- Pictures
- Related Online Video
- Flash Cards
Methods of Teaching :
- Class Discussion
- Group Discussion
- Asking Questions
- Explanation
- Role Modelling
- Role Delegation
Reference Materials :
- Scheme of Work
- Online Information
- Textbooks
- Workbooks
- 9 Year Basic Education Curriculum
- Workbooks
Content
TOPIC: Properties of materials (contd.) – Metals
SUB-TOPICS:
- Identification of Metals by Physical Properties
- Classification of Metals
Content Development (NOTES FOR FIRST LESSON/PERIOD ONE)
Sub-Topic 1: Identification of Metals by Physical Properties
Identification of metals can be defined as method used to differentiate one particular type of metal from another and from other materials which are non-metals.
Metals can be identified through their properties.
- Density – This is the weight of a metal and it varies from metal to metal. E.g. aluminium is light and lead is heavy in weight.
- Colour/Lustre– This is the appearance of a metal when the surface is polished. For example, when polished and examined under a microscope, copper presents a different appearance from a polished mild steel.
- Fusibility – This is the property of a metal which makes it melt and join with other metals while in a liquid form.
- Magnetic property – This is property that if a metal possesses it, it is attracted by a magnet. It is used to identify ferrous metals from non-ferrous metals. A magnet will attract ferrous metal while non-ferrous metals will not be attracted by a magnet.
- Elasticity or Stretching – This is the elastic property of a metal i.e. ability to stretch
- Brittleness – When a metal breaks suddenly or cracks easily, then it is said to possess brittleness e.g. glass.
- Conductivity of Heat – When heat spreads from one part of the body of a metal to other parts much more quickly than it does in other metals when heated this is conductivity of heat.
- Sound Test – This is the sound heard when any metallic materials is hit with a different type of materials.
The sound heard differs from metal to metal.
Other properties of metals are hardness, malleability and tenacity.
EVALUATION
Explain three properties of metal.
Content Development (NOTES FOR SECOND LESSON/PERIOD TWO)
Sub-Topic 2 – Classification of Metals
The metals used in engineering can be classified into two categories or classes.
- Ferrous metals and their alloys
- Non-ferrous metals and their alloys
Ferrous metal and their alloys – This is group of metals that contain iron. The metals have no iron. The metals are therefore, not magnetic. Examples are aluminum, copper, brass etc. Ferrous metals have the different grades of cast iron and steel. The different grades of cast iron are grey cast iron, white cast iron and malleable cast iron. They are used a lot in engineering to make different parts. Different grade of steel used in engineering construction and machine fabrication are mild steel, medium carbon steel, high speed steel, high tensile steel etc.
An alloy is combination of two or more metal to produce another metal e.g. metal A + metal B = metal C. Therefore metal C is an alloy of metal A and B e.g. chromium and nickel gives stainless steel.
Non-ferrous metal are no iron based which include these:
- Aluminum – This is a non-magnetic metal. When polished, it is silvery-white. It is very light in weight. Aluminum has a resistance to corrosion under normal atmospheric conditions. It is malleable, soft, ductile and a good conductor of heat.
- Copper – it is reddish brown or salmon pink in color. It is malleable and ductile. Copper is a good conductor of heat and electricity.
- Tin – it is bright silvery color. It is used as an alloying element. Tin is very soft and can hammer and rolled into very thin sheets. It has a high corrosion resistance.
- Lead – It is very heavy in weight and have grey color
- Zinc – It is bluish-white in color. Zinc is brittle and has a good resistance to rust.
Ferrous alloys are those types of metals that are produced when two or more non-ferrous metals are alloyed together. A good example of this is brass. Brass is the mixture of copper, tin and phosphorus. Metal can be found or purchased in different forms. The forms are:
- Round section and rectangular
- Tubular and flat section
- Plates and strips.
- Wires and channel.
EVALUATION
- Mention and explain five properties of metal.
- List four examples of non-ferrous metal.
READING ASSIGNMENT – Students should read about Metals
Text: NERDC Basic Technology for Junior Secondary School 1 Chapter 3 pages 21 – 26
WEEKEND ASSIGNMENT
- Metals can be identified through their _______ (a) properties (b) ability (c) energy (d) power
- Ferrous metal contain ______ (a) battery (b) chemical (c) salt (d) iron
THEORY
- What is an alloy?
- Mention four forms of metal
MARKING SCHEME
- A
- D
THEORY
- An alloy is a combination of two or more metals to produce another metal.
- Round section and rectangular, tubular and flat section, plates and strips, wires and channel
Presentation
The topic is presented step by step
Step 1:
The class teacher revises the previous topics
Step 2.
He introduces the new topic
Step 3:
The class teacher allows the pupils to give their own examples and he corrects them when the needs arise
Conclusion
The lesson is concluded when the class teacher wraps up the lesson by giving the pupils some notes.
The class teacher also goes round to make sure that the notes are well copied or well written by the pupils.
He or she does the necessary corrections when and where the needs arise.
Assignment
Prepare for the next lesson by reading about Properties of materials – Metals
