Lesson Notes By Weeks and Term v3 - Senior Secondary 1
Types and Uses of Metals
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Types and Uses of Metals
Download the Lessonotes Mobile Nigeria 2025 app for faster lesson access on Android and iPhone.
Subject: Metal Work
Class: Senior Secondary 1
Term: 3rd Term
Week: 2
Theme: Introduction To Metal Work And Metals
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Classify and define ferrous and non-ferrous metals Define Alloy State different types of alloys Carry out identification tests on different metals
This section provides a detailed explanation of the core concepts related to types and uses of metals. A. Classification of Metals Metals are primarily classified into two broad categories based on their iron content: i.
Ferrous Metals Definition: Ferrous metals are metals that contain iron as their primary component. They are typically magnetic and are prone to rust (corrosion) when exposed to moisture and oxygen, unless treated or alloyed.
Properties: Magnetic: Most ferrous metals are magnetic, making them easy to separate using magnets in recycling.
High Tensile Strength: Generally strong and durable, suitable for structural applications.
Hardness: Can be very hard, especially when carbon content is high or heat-treated.
Corrosion: Susceptible to rust unless protected by painting, coating, or alloying (e.g., stainless steel).
Examples and Uses in Nigeria: Mild Steel (Low Carbon Steel): Composition: Contains low carbon content (0.05% - 0.25%).
Properties: Malleable, ductile, good weldability, relatively soft.
Uses in Nigeria: Widely used in construction (reinforcement bars, roofing sheets), vehicle bodies, gates, window frames, general fabrication, agricultural implements (e.g., hoes, cutlasses), and local craftwork. It is the most common type of steel due to its versatility and cost-effectiveness.
Cast Iron: Composition: High carbon content (2% - 4%), with silicon.
Properties: Hard, brittle (poor tensile strength), excellent compression strength, good castability (can be melted and poured into complex shapes), good damping properties.
Uses in Nigeria: Manhole covers, engine blocks, heavy machinery parts, traditional cooking pots (dutch ovens), pipe fittings, machine tool bases, brake discs.
Wrought Iron: Composition: Nearly pure iron (very low carbon content, <0.08%) with fibrous slag inclusions.
Properties: Tough, ductile, malleable, easily forgeable, corrosion-resistant compared to mild steel (due to slag), non-magnetic when hot.
Uses in Nigeria: Historically used for decorative gates, railings, fences, and tools where ductility and resistance to fatigue were important. Less common now due to the widespread availability of mild steel, but its aesthetic qualities are still valued in artisan work. ii.
Non-Ferrous Metals Definition: Non-ferrous metals are metals that do not contain iron as their primary component. They are generally non-magnetic and often possess good corrosion resistance.
Properties: Non-Magnetic: Not attracted to magnets.
Corrosion Resistance: Many non-ferrous metals exhibit excellent resistance to rust and other forms of corrosion, making them suitable for outdoor or marine applications.
Lightweight: Often lighter than ferrous metals (e.g., aluminium).
Good Electrical & Thermal Conductivity: Excellent conductors of electricity and heat (e.g., copper, aluminium).
Malleability & Ductility: Easily shaped, drawn into wires, or hammered into sheets.
Examples and Uses in Nigeria: Aluminium: Properties: Very lightweight, excellent corrosion resistance (due to passive oxide layer), good thermal and electrical conductivity, highly ductile and malleable.
Uses in Nigeria: Roofing sheets, cooking utensils (pots, pans), beverage cans, window frames, light structural components, electrical cables (especially overhead lines), vehicle parts.
Copper: Properties: Excellent electrical and thermal conductivity, highly ductile and malleable, corrosion-resistant, distinctive reddish-brown colour.
Uses in Nigeria: Electrical wiring, plumbing pipes, roofing, heat exchangers, decorative items, motors, generators, local craft jewellery.
Zinc: Properties: Bluish-white metal, good corrosion resistance, low melting point.
Uses in Nigeria: Primarily used for galvanising steel (coating steel to prevent rust, e.g., galvanised roofing sheets, buckets), die casting (e.g., small engine parts), batteries.
Lead: Properties: Very dense, soft, malleable, low melting point, corrosion-resistant, toxic.
Uses in Nigeria: Car batteries, radiation shielding (limited), plumbing (historically, less common now due to toxicity), fishing weights.
Tin: Properties: Silvery-white, soft, malleable, corrosion-resistant, low melting point.
Uses in Nigeria: Used as a protective coating for steel (tin plating, e.g., "tin" cans for food preservation), in solders, and as an alloying element (e.g., bronze).
B. Alloy * Definition: An alloy is a metallic material composed of two or more elements, at least one of which is a metal. The elements are typically combined by melting them together and then allowing them to solidify. Alloying is done to enhance the properties of pure metals, such as strength, hardness, corrosion resistance, or aesthetic appeal, which are not present in point.
Uses in Nigeria: Used as a protective coating for steel (tin plating, e.g., "tin" cans for food preservation), in solders, and as an alloying element (e.g., bronze).
B. Alloy Definition: An alloy is a metallic material composed of two or more elements, at least one of which is a metal. The elements are typically combined by melting them together and then allowing them to solidify. Alloying is done to enhance the properties of pure metals, such as strength, hardness, corrosion resistance, or aesthetic appeal, which are not present in the individual pure metals.
Purpose: To improve properties like strength, hardness, toughness, ductility, wear resistance, corrosion resistance, electrical conductivity, magnetic properties, and aesthetics.
C. Types of Alloys Alloys can also be categorised based on their primary metallic component: i.
Ferrous Alloys (Iron-based alloys)
Steel: An alloy of iron and carbon, with carbon content typically between 0.2% and 2.1% by weight. Other alloying elements like manganese, chromium, nickel, molybdenum, etc., are added to modify its properties.
Carbon Steel: Steel where carbon is the main alloying element. Examples include mild steel (discussed above), medium carbon steel (used for axles, gears), and high carbon steel (used for cutting tools, springs due to its hardness).
Uses in Nigeria: Structural components, tools, automotive parts, machinery.
Stainless Steel: Composition: Contains a minimum of 10.5% chromium, which provides excellent corrosion resistance by forming a passive oxide layer on the surface. May also contain nickel, molybdenum.
Properties: High corrosion resistance, attractive finish, hygienic, good strength.
Uses in Nigeria: Kitchen sinks, surgical instruments, cutlery, food processing equipment, decorative architecture, industrial tanks and pipes. ii. Non-Ferrous Alloys (Alloys where the primary component is a non-ferrous metal)
Brass: Composition: Alloy of copper and zinc.
Properties: Good workability, attractive gold-like colour, good corrosion resistance, good electrical conductivity.
Uses in Nigeria: Plumbing fittings, electrical connectors, decorative items (e.g., traditional Nigerian jewellery, ornaments), musical instruments, hinges, locks.
Bronze: Composition: Alloy of copper and tin (historically), but can also include other elements like aluminium, manganese, or zinc.
Properties: Harder and stronger than copper, good corrosion resistance, excellent wear resistance, attractive appearance.
Uses in Nigeria: Sculptures (e.g., Benin Bronzes), bearings, gears, marine fittings, bells, commemorative items.
Duralumin: Composition: An aluminium alloy with copper as the main alloying element (approx. 4%), along with magnesium and manganese.
Properties: High strength-to-weight ratio, good ductility, but less corrosion resistant than pure aluminium.
Uses in Nigeria: Aircraft components, lightweight structural applications, bicycle frames.
Pewter: Composition: Primarily tin, alloyed with copper, antimony, and sometimes bismuth (traditionally with lead, but now lead-free).
Properties: Soft, malleable, low melting point, attractive silvery-grey finish.
Uses in Nigeria: Decorative items, traditional plates, tankards, jewellery.
Solder: Composition: Typically an alloy of tin and lead (though lead-free solders are now common, using tin with silver or copper).
Properties: Low melting point, good flow characteristics, adheres well to other metals.
Uses in Nigeria: Joining electrical components, plumbing joints, sheet metal work. D. Identification Tests on Different Metals Identifying metals is crucial for proper material selection and processing. Practical and relatively safe methods suitable for a Nigerian classroom include:
1. Visual Inspection: Method: Observe the colour, lustre (shininess), surface texture, and any signs of corrosion.
Observations: Reddish-brown: Copper Silvery-white/Grey: Aluminium, Stainless Steel, Mild Steel, Zinc, Tin, Lead (Lead is duller, heavier, and softer).
Gold-like: Brass Shiny/Metallic: Most pure metals and alloys.
Dull/Oxidized: Corroded iron/steel (rust), dull lead.
Limitations: Can be misleading if surfaces are heavily oxidised or painted.
2. Magnetic Test: Method: Use a strong magnet to test if the metal sample is attracted.
Observations: Attracted: Ferrous metals (e.g., mild steel, cast iron, most carbon steels). This indicates the presence of iron.
Not Attracted: Non-ferrous metals (e.g., aluminium, copper, brass, bronze, zinc, lead, tin). Stainless steel can sometimes be non-magnetic depending on its specific alloy composition (e.g., austenitic stainless steel).
Significance: Quickly differentiates most ferrous from non-ferrous metals.
3. Weight/Density Test (Relative Weight): Method: Compare the weight of similarly are heavily oxidised or painted.
2. Magnetic Test: Method: Use a strong magnet to test if the metal sample is attracted.
Observations: Attracted: Ferrous metals (e.g., mild steel, cast iron, most carbon steels). This indicates the presence of iron.
Not Attracted: Non-ferrous metals (e.g., aluminium, copper, brass, bronze, zinc, lead, tin). Stainless steel can sometimes be non-magnetic depending on its specific alloy composition (e.g., austenitic stainless steel).
Significance: Quickly differentiates most ferrous from non-ferrous metals.
3. Weight/Density Test (Relative Weight): Method: Compare the weight of similarly sized pieces of different metals by hand.
Observations: Very Light: Aluminium, Duralumin.
Medium Weight: Mild steel, Brass, Bronze.
Very Heavy: Lead, Cast Iron, Copper (relatively heavy).
Significance: Provides an indication of the metal's density. For instance, aluminium is noticeably lighter than steel of the same size.
4. Hardness Test (Scratch Test): Method: Attempt to scratch one metal sample with another, or with a known hard object (e.g., a file, steel nail). Observe if a permanent scratch is made.
Observations: Soft: Lead, Tin (can be scratched easily with a fingernail or mild steel).
Medium Hardness: Aluminium, Copper, Mild Steel (can be scratched by a file, but not easily by fingernail).
Hard: High carbon steel, some cast irons, hardened tool steel (resists scratching by most common objects).
Significance: Indicates the metal's resistance to deformation and wear.
5. Sound Test (Tapping Test): Method: Tap the metal sample with a small hammer or drop it gently onto a hard surface and listen to the sound produced.
Observations: Dull Thud: Lead, Cast Iron (due to its brittleness and internal structure).
Clear Ring: Steel, Brass, Copper, Bronze, Aluminium (indicates good elasticity).
Significance: Can help differentiate between very brittle metals like cast iron and more ductile ones. (Note for teachers: More advanced tests like spark testing for various steels or specific chemical tests are typically performed in industrial settings or advanced labs due to safety concerns and equipment requirements. For SS1, focus on the practical and safe tests listed above.)
Teacher Activities: Introduction (10 minutes): Teacher reviews previous lesson on properties of metals (e.g., malleability, ductility, conductivity). Teacher introduces the topic "Types and Uses of Metals" by asking students to name common metal objects they see daily in their environment (e.g., cars, cooking pots, gates, wires). Teacher explains that these objects are made from different types of metals chosen for specific purposes.
Presentation of Key Concepts (25 minutes): Teacher uses prepared charts, diagrams, or digital presentations to explain the classification of metals into ferrous and non-ferrous. Teacher defines ferrous and non-ferrous metals, highlighting their key properties (magnetic, corrosion resistance, strength, weight). Teacher presents samples of various ferrous metals (e.g., mild steel rod, cast iron pot piece, wrought iron decorative piece) and non-ferrous metals (e.g., aluminium sheet, copper wire, brass fitting, zinc galvanised steel offcut, lead weight if safe). Teacher discusses the properties and common uses of each metal in the Nigerian context, linking them to the samples. Teacher defines "alloy" and explains the purpose of alloying with real-world examples (e.g., why steel is stronger than pure iron, why brass is used for plumbing instead of pure copper for certain fittings). Teacher explains different types of alloys (ferrous and non-ferrous alloys) with examples like steel (stainless steel), brass, bronze, duralumin, pewter, and solder, detailing their compositions and uses in Nigeria. Demonstration of Identification Tests (20 minutes): Teacher demonstrates the practical identification tests: Visual Inspection: Showing differences in colour, lustre, and texture.
Magnetic Test: Using a magnet on different samples (mild steel, aluminium, copper, cast iron).
Weight/Density Test: Having students compare weights of similarly sized samples by hand (e.g., aluminium vs. steel).
Hardness Test: Gently scratching samples with a file or a steel nail to show differences in hardness (e.g., lead vs. steel).
Sound Test: Tapping different metal samples with a small hammer or dropping them (safely) onto a hard surface. Teacher emphasises safety precautions, especially when handling samples with sharp edges or during tapping tests. Guided Practice and Discussion (15 minutes): Teacher poses questions to stimulate discussion on the observed properties and uses. Teacher guides students to classify unfamiliar metal objects found in the classroom or workshop. Teacher facilitates group work where students attempt to identify unknown metal samples using the demonstrated tests.
Conclusion (5 minutes): Teacher summarises the key learning points on classification, alloys, and identification. Teacher assigns independent practice/homework.
Student Activities: Observation and Participation: Students observe the metal samples and demonstrations keenly. They actively participate in discussions and Q&A sessions.
Note-Taking: Students take detailed notes on the definitions, properties, examples, and uses of different metals and alloys, and the steps for identification tests.
Practical Engagement (Group Work): In small groups, students handle provided metal samples (under teacher supervision). Students perform the visual, magnetic, relative weight, and simple hardness tests on a set of labelled and unlabelled metal samples. Students record their observations and classify the samples into ferrous or non-ferrous categories and identify potential alloys based on characteristics.
Reporting: Each group briefly reports their findings and classifications of the tested samples.
This topic on types and uses of metals has profound real-life applications and integrates with various aspects of Nigerian life and economy. Construction and Infrastructure Development: Application: Students learn why mild steel (a ferrous metal and an alloy) is the backbone of Nigerian construction, used for reinforcing concrete (rebar), fabricating gates, window frames, and roofing trusses due to its strength and affordability. They also understand the role of aluminium (a non-ferrous metal) for lightweight, corrosion-resistant roofing sheets and window frames, especially in coastal areas where rust is a major concern.
Integration: This connects to local building practices, understanding material costs, durability, and the importance of corrosion protection (e.g., painting steel gates or using galvanised iron sheets).
Local Manufacturing and Artisanship: Application: The knowledge of various metals and alloys is crucial for local artisans and small-scale manufacturers. For example, understanding that brass (a non-ferrous alloy) is malleable and has a desirable aesthetic helps artisans creating decorative items, jewellery, and traditional artworks (e.g., the historical "Benin Bronzes" which are technically brass or bronze). Cast iron (a ferrous metal) is used for durable cooking pots and local machinery parts, highlighting its excellent casting properties.
Integration: This directly relates to vocational skills development, encouraging entrepreneurial opportunities in metal fabrication, welding, and craft industries within local communities. Household Utilities and Electrical Systems: Application: Students grasp why copper (a non-ferrous metal) is indispensable for electrical wiring in homes and industries across Nigeria due to its superior electrical conductivity. They will also understand why aluminium is used for cooking utensils (pots, pans) due to its good thermal conductivity and light weight, and how stainless steel (a ferrous alloy) provides hygiene and corrosion resistance for sinks and cutlery.
Integration: This knowledge helps in making informed decisions about product quality, electrical safety, and maintenance of household items. It also highlights career paths in electrical installation and appliance repair.