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This lesson covers the sources and origins of metals, polymers, and textiles, as required by AQA GCSE D&T (8552), Section 3.2.4. Understanding where these materials come from, how they are obtained, and the environmental and ethical issues associated with their extraction is essential for responsible design.
Metals are extracted from ores — naturally occurring rocks that contain metal compounds (usually metal oxides or sulphides). The ore must be mined, then the metal must be separated from the ore through a process called extraction or smelting.
| Metal | Ore | Extraction Method | Primary Source Countries |
|---|---|---|---|
| Iron | Haematite (iron oxide) | Blast furnace (reduction with carbon/coke) | Australia, Brazil, China, India |
| Aluminium | Bauxite (aluminium oxide) | Electrolysis (very energy-intensive) | Australia, Guinea, Brazil, Jamaica |
| Copper | Chalcopyrite (copper iron sulphide) | Smelting and electrolytic refining | Chile, Peru, China, DRC |
| Tin | Cassiterite (tin oxide) | Smelting with carbon | China, Indonesia, Myanmar |
| Zinc | Sphalerite (zinc sulphide) | Roasting and electrolysis | China, Australia, Peru |
| Gold | Native gold (free metal) or in quartz | Cyanide leaching or mercury amalgamation | China, Australia, Russia, USA |
| Category | Contains Iron? | Magnetic? | Rusts? | Examples |
|---|---|---|---|---|
| Ferrous | Yes | Yes (most) | Yes (unless protected) | Mild steel, cast iron, stainless steel, high-carbon steel |
| Non-ferrous | No | No | No (but may corrode) | Aluminium, copper, zinc, tin, gold, silver, titanium |
An alloy is a mixture of two or more metals (or a metal and a non-metal) combined to improve properties.
| Alloy | Base Metals | Key Property | Common Use |
|---|---|---|---|
| Stainless steel | Iron + chromium (+ nickel) | Corrosion-resistant | Cutlery, kitchen sinks, medical instruments |
| Brass | Copper + zinc | Attractive gold colour, easy to machine | Door handles, musical instruments, plumbing fittings |
| Bronze | Copper + tin | Hard, corrosion-resistant | Bearings, sculptures, bells |
| Duralumin | Aluminium + copper + magnesium | Strong and lightweight | Aircraft structures |
| Solder | Tin + copper (lead-free) | Low melting point | Electronic circuit board assembly |
AQA Exam Tip: Know the difference between ferrous and non-ferrous metals, and be able to give examples of each. Also know at least three common alloys, their compositions, and their uses. Alloy questions appear frequently in the exam.
Polymers (plastics) are large molecules made by joining many small molecules (monomers) together in a process called polymerisation.
The vast majority of polymers are derived from crude oil (a fossil fuel). The process is:
| Property | Thermoplastics | Thermosetting Polymers |
|---|---|---|
| Structure | Long polymer chains with weak intermolecular bonds | Polymer chains with strong cross-links between them |
| Heat behaviour | Soften when heated; can be reshaped | Do NOT soften when heated; remain rigid |
| Recyclability | CAN be recycled (reheated and reformed) | CANNOT be recycled by reheating |
| Examples | HDPE, PP, PET, ABS, acrylic (PMMA), nylon, PVC | Epoxy resin, polyester resin, melamine, urea formaldehyde, Bakelite |
| Common uses | Bottles, packaging, pipes, car parts, clothing | Circuit boards, kitchen worktops, adhesives, composite matrices |
| Bioplastic | Source | Properties | Use |
|---|---|---|---|
| PLA (polylactic acid) | Corn starch, sugarcane | Biodegradable, compostable, transparent | Packaging, 3D printing filament, disposable cups |
| PHA (polyhydroxyalkanoate) | Bacterial fermentation of plant sugars | Biodegradable, flexible or rigid | Packaging, medical implants |
| Starch-based polymers | Potato, corn, or wheat starch | Biodegradable, water-soluble | Packaging peanuts, compostable bags |
AQA Exam Tip: The difference between thermoplastics and thermosetting polymers is one of the most commonly tested topics. The key point: thermoplastics CAN be recycled (reheated and reshaped); thermosets CANNOT (the cross-links prevent remelting). This has major implications for sustainability and material selection.
Textiles are flexible materials made from fibres. Fibres can be natural (from plants or animals) or synthetic (man-made from polymers).
| Fibre | Source | Key Properties | Common Use |
|---|---|---|---|
| Cotton | Cotton plant (seed hairs) | Soft, breathable, absorbent, comfortable | T-shirts, jeans, bed linen, towels |
| Wool | Sheep fleece | Warm, naturally flame-retardant, elastic, moisture-wicking | Jumpers, suits, blankets, carpets |
| Silk | Silkworm cocoons | Lustrous, smooth, strong, lightweight | Formal clothing, ties, scarves |
| Linen | Flax plant (stem fibres) | Strong, cool to wear, crisp texture | Summer clothing, tablecloths |
| Hemp | Hemp plant (stem fibres) | Very strong, durable, grows without pesticides | Bags, rope, clothing, canvas |
| Fibre | Source | Key Properties | Common Use |
|---|---|---|---|
| Polyester (PET) | Crude oil | Strong, wrinkle-resistant, quick-drying, cheap | Most clothing globally, sportswear, bedding |
| Nylon (polyamide) | Crude oil | Very strong, elastic, abrasion-resistant | Tights, rucksacks, carpets, toothbrush bristles |
| Acrylic | Crude oil | Soft (wool substitute), lightweight, warm | Knitwear, fake fur, blankets |
| Elastane (Lycra/Spandex) | Crude oil | Extremely elastic (stretches to 5-8x its length) | Sportswear, underwear, swimwear |
Many textiles are blends of natural and synthetic fibres to combine the best properties of each:
| Blend | Benefit |
|---|---|
| Polycotton (polyester + cotton) | Cotton's comfort and breathability with polyester's durability and crease-resistance |
| Wool + nylon | Wool's warmth with nylon's strength and abrasion resistance |
| Cotton + elastane | Cotton's comfort with elastane's stretch (e.g. stretch jeans) |
However, blended fabrics are more difficult to recycle because the different fibre types must be separated before they can be reprocessed — a significant sustainability challenge.
AQA Exam Tip: Be able to classify fibres as natural or synthetic, give examples of each, and explain the advantages and disadvantages of blended fabrics. The sustainability angle (blends are harder to recycle) is increasingly important in exam questions.
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