Lesson Notes By Weeks and Term v4 - JHS 3

Lesson Video

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Performance objectives

• Define smart and modern materials.
• Discuss reasons for using these materials in production.
• Identify examples of these materials in everyday life.
• Explain the benefits for Ghana's economy and environment.

Lesson summary

This lesson introduces learners to the exciting world of smart and modern materials. We will move beyond traditional materials like wood, metal, and plastic to explore materials that have been engineered with special properties. We will learn what makes a material "smart" or "modern" and, most importantly, discuss the reasons why designers and engineers choose to use them to create innovative and useful products. Understanding these materials is important because they are used to solve modern problems in everything from medicine and safety to fashion and sports, opening up new possibilities for Ghanaian innovators and entrepreneurs.

Lesson notes

This section breaks down the core ideas you need to understand. A. What are Smart and Modern Materials? Smart Materials: Definition: Smart materials are materials whose properties can be significantly changed in a controlled way by external stimuli (outside influences). Think of them as materials that can "sense" and "react" to their environment. Analogy: Imagine the Mimosa plant (*nkontomire* leaf) we see in Ghana. When you touch it, it folds its leaves. It is reacting to a stimulus (touch). Smart materials do something similar, but with stimuli like heat, light, pressure, or electricity. The Key Idea: They have a property that is not fixed; it can change and then often change back. Modern Materials: Definition: Modern materials are materials that have been developed recently through scientific advancement. They do not necessarily "react" like smart materials, but they have superior properties (like being extremely strong but lightweight) compared to traditional materials. The Key Idea: They are man-made and engineered to perform a specific function exceptionally well. B. Types of Smart Materials and Reasons for Their Use

Let's look at some examples, their properties, and *why* we use them.

| Name of Material | Description & How it Works | Key Property & Stimulus | Products Made & Reasons for Use (Advantages) | | :--- | :--- | :--- | :--- | | Thermochromic Materials | These materials change colour when their temperature changes. The molecules in their pigments rearrange at different temperatures, which changes the way they absorb and reflect light. | Changes colour in response to Heat (Temperature). | Baby Feeding Spoons, Kettles, Mugs: • Safety: The primary reason is safety. The spoon or mug changes colour to warn you if food or a drink is dangerously hot, preventing burns. Food Packaging: • Quality Control: It can show if a food product has been stored at the wrong temperature, indicating it might be spoiled. Mood Rings, T-shirts: • Aesthetics/Novelty: Used for fun and decoration. The material reacts to body heat, creating a changing visual effect. | | Photochromic Materials | These materials change colour when exposed to ultraviolet (UV) light. When UV light (like from the sun) hits the material, its molecules change shape, causing it to darken. When the UV light is removed, they change back. | Changes colour (darkens) in response to UV Light. | "Transitions" Eyeglass Lenses: • Convenience & Health: This is the main reason. It combines prescription glasses and sunglasses into one pair. This protects the user's eyes from harmful UV rays automatically when they go outside into the bright Ghanaian sun, and become clear again indoors. It's more convenient than carrying two pairs of glasses. UV-sensitive Beads/Wristbands: • Health & Safety Awareness: These change colour to indicate the strength of the sun's UV rays, reminding people to apply sunscreen and avoid sunburn. | | Shape Memory Alloys (SMAs) | These are metal alloys that can be deformed (bent out of shape) when cool, but will return to their original, "remembered" shape when heated. A common SMA is Nitinol (Nickel-Titanium). | Returns to a pre-set shape when exposed to Heat. | Braces for Teeth (Orthodontics): • Efficiency & Comfort: When the dentist fits the brace wire, it is cool and easy to shape. The heat from the patient's mouth then activates it. The wire tries to return to its original straight shape, applying a gentle, constant pressure to move the teeth over a long time. This is more effective than traditional steel wires. Stents for Arteries: • Medical Application: A small, collapsed stent can be inserted into a blocked artery. Body heat causes it to expand to its "remembered" open shape, holding the artery open and improving blood flow. Frames for Glasses: • Durability: You can bend or crush the frames, and with a little heat (like from warm water), they will pop back into their original shape, making them very hard to break. | C. Types of Modern Materials and Reasons for Their Use

| Name of Material | Description & Properties | Products Made & Reasons for Use (Advantages) | | :--- | :--- | :--- | | Carbon Fibre | This is a polymer made of long, thin strands of carbon atoms. It is woven into a fabric and then combined with a resin to form a strong, solid material. Its key properties are: extremely high strength-to-weight ratio (very strong but very light) and stiffness. | High-Performance Bicycles, Racing Car Parts, Modern Aircraft (e.g., wings), Fishing Rods, Tripods. | • Performance & Fuel Efficiency: Because it is so light and strong, it makes cars and planes lighter, so they use less fuel. It makes bicycles lighter, so they can go faster. • Strength & Durability: It can withstand great force without breaking or bending, making products more durable and reliable than if they were made from steel or aluminium. | | Kevlar | This is a synthetic fibre known for its incredible tensile strength (resistance to being pulled apart) and heat resistance. It is five times stronger than steel of the same weight. | Bulletproof Vests, Motorcycle Safety Clothing, Puncture-resistant Tyres, Firefighter Uniforms. | • Protection & Safety: This is the number one reason. Its ability to absorb and dissipate massive amounts of energy makes it ideal for stopping bullets or preventing sharp objects from piercing through. It is used to save the lives of police, soldiers, and other security personnel. • Durability: In tyres, it provides a protective layer that resists punctures from nails or glass on the road. |