unit: materials - la salle...

Materials used in Technology Technologies 2n 2014/15

UNIT: Materials. Materials for technical useIn this unit you will find out the answers to these questions:a) How are raw materials classified?b) Where do different types of material come from?c) What uses do they have?d) What are the factors that determine the choice of material for manufactured goods?e) In what ways are materials important in technological development?

INDEX:1. Raw materials2. Materials. Materials for technical use3. Manufactured goods. Usable good.4. Properties of materials

KEY WORDSAlloy: aleaciónClay: fine-grained, flexible, humid earth that becomes hard when fired, barroCoal: carbónConcrete: hormigónCork: corchoDevelopment: improvement, progressFastener: object or apparatus used to join or connect pieces together, cremallera, cierreFerrous: containing ironHide: the skin of an animal processed to be used to make clothes and other goods, cuero (Leather: piel)Iron: hierroIron ore: rock containing ironLog: leño, tronco Lycra®: an elastic synthetic textile.Manufactured goods: products created by humans to satisfy our needs and improve our standard of livingMarble: a type of stone used for floors or other surfaces, mármolMaterial: substance that has been prepared for making different types of productsOre: mena, mineralPlaster: a mixture of a specific powdered rock and water, used to cover walls. Becomes had when dry, yesoPlank: wood cut into flat boards of varying size and thickness, tablaQuarry: the place where stone is taken from the ground near the earth’s surface, cantera, excavación Raw: crudoRaw material: the basic natural material we use to manufacture other products, materias primasScratch: make a mark on the surface of something, rasguño, arañazoSpread: cover a larger area, expandirseStainless: inoxidableSteel: a very hard metal made of iron and carbon, aceroSource: originThread: a very thin piece of cotton or other fibre used for sewing or weaving, hiloWelding: some materials can be used to weld 2 pieces of the same or different materials together, soldarWire: a thin metal filament or cable, alambre, cable

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1. Raw materialsAs members of a technological society, we use a great variety of objects in our every day, objects that range from a coffee maker to an aeroplane.

Raw materials are substances that are extracted directly from natural objects.

For example:Look at the pictures below. What materials can we process form each one?

Sheep Cotton

Oil platform Iron ore

Wool

comes from

the hair of sheepCotton the plant of cottonPetroleum, oil below the sea, extracted with oil platformsSteel Iron ore

The naturals materials from which materials for technical use are obtained are raw materials. Wood, cotton, oil, wool, minerals and marble are examples of raw materials

2. Materials. Materials for technical useRaw materials are transformed by physical and chemical processes into the various types of materials that are used for manufacturing. They are prepared so that they are ready to use for making many different products.For example: stainless steel is obtained from the transformation of iron ore.

The materials used for making objects are materials for technical use, which we also call semi-manufactured or semi-finished products.Common examples of materials for manufacturing: paper, planks of wood, plastic, metal and glass

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3. Manufactured goods. Usable good.A manufacture good is any object created by humans to satisfy their needs and improve their standard of livingExamples of usable goods: textbook, chair, desk, watch, sweater…

In conclusion, materials for technical use are used to manufacture useful objects and are the result of the transformation of raw materials:

Raw materials Material/Material for technical use

Manufactured goods products /

Usable goods

Trees (wood) are cut into longs

Longs are made into planks of

wood

Planks are used to make furniture

(bookshelf)

Classification of Material for technical use (Technical materials):Material for technical use can be classified in many different ways, but we present two classifications:

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Technical materials: common materials used to make manufactured goods:

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4. Properties of materialsWe use different materials in different ways depending on their properties:4.1 PHYSICAL PROPERTIESThese properties relate to how materials react to external simuli (electricity, light, heat or the applying of various forces…).

Types of physical properties:Electrical, Thermal, Acoustic, Magnetic, Optical, Mechanical properties…4.1.1 Electrical properties: what happens when an electrical current is passed through a material?

Electric cables are covered with plastic (an insulating material) and inside they contain copper wires (a conductive material)4.1.2 Thermal properties: what happens when a material is heated?

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4.1.3 Acoustic properties: can you hear sound through a material?

4.1.4 Magnetic properties:

4.1.5 Optical properties: can you see light through a material?

4.1.6 Mechanical properties: what happens to a material when external forces are applied?The mechanical properties determine the behaviour of a technical material when it’s subjected to external forces or conditions.

- Mechanical strength:The mechanical strength depends on the type of force that acts upon them. There are several types of strength: tensile, compressive, flexural, torsional and shear strength.

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- Elasticity and Plasticity:

- Malleability and ductility:

- HardnessA hard material is not easily scratched by another material. The Mohs scale of minerals was created by the geologist Friedrich Mohs and the minerals are graded from 1 to 10 according to how hard they are. Here are some examples:

- Toughness and brittlenessFor example: if we hit a metal object (a bell) with a hammer, it doesn’t break. If we hit a mirror, it breaks easily

4.1.7 Other properties:

4.2 CHEMICAL PROPERTIESWe can see these properties when chemical composition of a material changes because it interacts with other substances.- Oxidation properties:This happens when a mineral reacts with oxygen in the air or water. Metals are the most sensitive materials to oxidation. The reddish-brown substance produced is called rust.

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4.3 ECOLOGICAL PROPERTIESMaterials are classified according to the impact they have on the environment.

Some materials come from renewable raw materials. These raw materials can be regenerated

Activities:1. There are some raw materials. Put them in the correct column. Add other materials to complete de table:

Animal origin Vegetable origin Mineral origin

2. Materials:a) Which raw material do these materials come from?

b) write 3 objects/manufactured goods that can we make from those materials3. There are 3 rows of words. Which is the odd one out? Why?a) rubber, PVC, glass, nylonb) bookshelf, chair, brick, paperc) marble, plaster, sand, thread4. Classify the following into raw materials, materials and manufactured goods: oil, clay, iron, plates, table, copper as a mineral, a tree trunk, sand glassware5. From what materials can the following manufactured goods be made? A glass – a photo frame – a bridge - a bookshelf - a sculpture – a shirt – a plate

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6. Match the items from the column of raw materials with the materials (technical materials) ant the objects in the column of manufactured goods. Some raw materials and materials can be matched with more one item from the other column.

7. Use your dictionary and classify the following textile materials into natural or synthetic: polyester, cotton, polyamide, wool, jute, nylon, rayon, silk, linen, viscose, Lycra®8. Match the materials:

9. Which of the following materials are electrical conductors and which are insulators?Plastic, Aluminium, Wood, Iron, Copper10. Choose the correct option:a) To find out if a material is a thermal conductor you can touch it. If it becomes cold/warm, it’s a thermal conductorb) Metal/Wood is the material that is most sensitive to thermal expansionc) A characteristic of materials used for welding is fusibility/conductivity.

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11. Complete the table: write YES if the manufactured goods can be made from materials with this optical property. Write NO if they can’tMaterial Transparent Translucent OpaqueWindowDoorBookLight bulb12. What materials would you use to soundproof a room? Why?13. Write a list of 5 manufactured goods made with elastic materials14. Think of 3 examples of malleable materials and 3 more of ductile materials. Can any materials be both malleable and ductile?15. Order from greater to lesser hardness: plasticine, glass, plaster, ceramics, diamond and talc.16. Match the opposites: hardness, brittleness, expansion, softness, impermeability, toughness, permeability, contraction.17. Can a hard material be brittle? Explain your answer with an example18. Which has a higher density, cork or marble? Why?19. Oxidation. Which sentences are true or false?a) Rust is another name for oxidised ironb) The roofs of some old buildings are reddish-brown because they contain copper.c) Gold oxidises easily20. Write the waste products under the correct container they belong in:

21. Complete the following table with: marble, PVC, porcelain, aluminium, methacrylate, glass, wood

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22. Choose the correct answer:

23. Summary activity: choose the correct word from the list and put it in the correct place

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unit: materials - la salle...

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