Lesson Notes By Weeks and Term v5 - Grade 7

Lesson Video

This page supports the lesson note with a companion video and a short classroom-ready summary.

For class groups and homework, share this lesson page so learners also get the summary, objectives, and full lesson context.

Performance objectives

• Identify and classify common materials (natural vs. manufactured).
• Describe the properties of wood, metal, and plastic.
• Identify and safely use at least five basic hand tools.
• Explain the principles of cutting, shaping, and joining.
• Understand the importance of safety precautions.

Lesson summary

This week, we delve into the exciting world of processing materials, focusing on basic materials and the tools we use to shape them. Understanding how materials are processed is fundamental to creating almost everything around us, from the desks we sit at in school to the houses we live in. In a country like South Africa, with its rich natural resources and vibrant manufacturing sector, knowing how to work with different materials is a valuable skill that can open doors to various career paths, such as carpentry, metalworking, construction, and even entrepreneurship.

Lesson notes

2.1 Materials: Natural vs. Manufactured Materials are the building blocks of everything we create in technology. They can be broadly classified into two categories: Natural Materials: These are materials found in nature and haven't undergone significant changes from their original state.

Examples include: Wood: Derived from trees. Different types of wood (e.g., pine, oak, mahogany) have different properties, such as hardness, grain, and durability. Think of the acacia trees in the Kruger National Park. Pine wood is common for furniture-making.

Stone: Rocks and minerals used for construction, decoration, and tools. Granite, sandstone, and slate are examples. Consider the stone buildings in historical towns like Graaff-Reinet.

Leather: Made from animal hides. Used for clothing, shoes, and upholstery. Many traditional South African crafts utilize leather.

Clay: A type of soil that can be molded when wet and hardened when fired. Used for pottery, bricks, and tiles. Think of the traditional Zulu pottery.

Manufactured Materials: These are materials that have been processed or combined from natural resources through human intervention.

Examples include: Metal: Extracted from ores and processed. Common metals include steel, aluminum, copper, and iron. Used in construction, vehicles, tools, and electronics. Steel is vital for construction in South Africa.

Plastic: Made from petroleum or natural gas. Versatile, lightweight, and durable. Used in packaging, toys, furniture, and many other products. Plastic products are widely used across South Africa.

Glass: Made from sand, soda ash, and limestone. Transparent, strong, and recyclable. Used in windows, bottles, and screens.

Concrete: A mixture of cement, water, sand, and gravel. Used in construction. 2.2 Properties of Common Materials The properties of a material determine how it can be used.

Here are some key properties: Strength: The ability to withstand force without breaking.

Tensile strength: Resistance to being pulled apart. Steel has high tensile strength, making it ideal for bridges.

Compressive strength: Resistance to being crushed. Concrete has high compressive strength, ideal for building foundations.

Hardness: Resistance to being scratched or dented. Diamonds are the hardest known material.

Durability: The ability to withstand wear and tear over time.

Flexibility: The ability to bend without breaking. Rubber is very flexible.

Malleability: The ability to be hammered or pressed into shape without breaking. Gold is very malleable.

Ductility: The ability to be drawn into a wire without breaking. Copper is very ductile, making it suitable for electrical wiring.

Conductivity: The ability to conduct heat or electricity. Copper and aluminum are good conductors of electricity.

Density: The mass per unit volume. Iron is denser than wood.

Example: Consider the use of wood for making a school desk.

Wood is chosen because: It has adequate strength to support books and writing. It is relatively easy to shape and join using common woodworking tools. It is readily available and relatively affordable in South Africa. It can be treated to improve its durability and resistance to pests. 2.3 Basic Hand Tools and Their Uses Understanding the tools used to process materials is crucial.

Here are some common tools and their uses: Hammer: Used for driving nails, shaping metal, and breaking materials.

Safety: Wear safety glasses.

Screwdriver: Used for driving and removing screws. Different types of screwdrivers (Phillips, flathead) are used for different types of screws.

Safety: Use the correct size screwdriver for the screw.

Saw: Used for cutting wood, metal, and plastic. Different types of saws (handsaw, hacksaw, coping saw) are used for different materials and cuts.

Safety: Use a vice to secure the material, and keep your fingers away from the blade.

Pliers: Used for gripping, bending, and cutting wires and other materials.

Safety: Do not use pliers to cut live electrical wires unless they are insulated.

Wrench (Spanner): Used for tightening and loosening nuts and bolts.

Safety: Use the correct size wrench to avoid damaging the nut or bolt.

File: Used for smoothing and shaping metal and wood.

Safety: Use a handle to protect your hand.

Chisel: Used for shaping wood, stone, or metal by removing small pieces.

Safety: Wear safety glasses and strike the chisel head squarely with a hammer.

Measuring Tape/Ruler: Used for accurately measuring materials. Accurate measurements are crucial for successful projects. 2.4 Cutting, Shaping, and Joining Materials Cutting: Removing material to create a desired shape or size. Saws, knives, and scissors are used for cutting.

Shaping: Altering the form of a material. Bending, hammering, and molding are methods of shaping.

Joining: Connecting two or more pieces of material together. Gluing, screwing, welding, nailing, and soldering are methods of joining.