Materials

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  • Very helpful with low ability students. Thank you Javier.
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Materials

  1. 1. Why do we use different materials to make different things ?
  2. 2. Why do we use different materials to make different things? <ul><li>Different materials have different characteristics: </li></ul><ul><li>Properties (weight, hardness, elasticity, …) </li></ul><ul><li>Price </li></ul><ul><li>Appearance </li></ul><ul><li>Availability </li></ul><ul><li>Easiness/difficulty of use </li></ul><ul><li>Effects on health </li></ul><ul><li>Effects on environment </li></ul>
  3. 3. Most important types of materials Metals (eg steel, copper) Wood (eg oak, MDF) Plastic (eg vinyl, PVC) Fabric (eg cotton, polyester) Ceramic (eg clay, porcelain)
  4. 4. Some important properties <ul><li>Colour, shininess </li></ul><ul><li>Weight, density </li></ul><ul><li>Strength, toughness, hardness, brittleness </li></ul><ul><li>Feel, texture </li></ul><ul><li>Resistance to heat, resistance to corrosion </li></ul><ul><li>Conductivity/insulation (electrical or heat) </li></ul><ul><li>Flexibility </li></ul><ul><li>Ability to see through: opaque, translucent, transparent </li></ul><ul><li>Elasticity, plasticity </li></ul><ul><li>Malleability </li></ul><ul><li>Ductility </li></ul>
  5. 5. Which materials would you use for these objects? Why? <ul><li>Chair </li></ul><ul><li>Pan </li></ul><ul><li>Book </li></ul><ul><li>Wire </li></ul><ul><li>Jacket </li></ul>
  6. 6. <ul><li>A CHAIR could be made of wood because </li></ul><ul><li>The wood has a good appearance </li></ul><ul><li>It is strong, tough </li></ul><ul><li>It can be environmentally friendly (it depends on the type of </li></ul><ul><li>wood) </li></ul><ul><li>It is not usually expensive (it depends on the type of wood) </li></ul><ul><li>But if we want a CHAIR for the outside, maybe it is better to make it of plastic : </li></ul><ul><li>The plastic has a better resistance to humidity, </li></ul><ul><li>so it will last longer </li></ul><ul><li>It has some flexibility, so the chair can be more </li></ul><ul><li>confortable </li></ul><ul><li>It is cheaper than wood </li></ul><ul><li>It is not as heavy as wood </li></ul>
  7. 7. <ul><li>A PAN is made of metal because: </li></ul><ul><li>It is a good conductor of heat, so when it on the fire it can transmit the heat to the meat we put on it. </li></ul><ul><li>But at the same time, it has a good resistance to heat, so it does not melt when it is on the fire </li></ul><ul><li>We can make the handle of plastic , because it is a good insulator of heat and it has a good texture </li></ul><ul><li>A Book is made of paper (and cardboard) because: </li></ul><ul><li>It has a good texture, so it is nice to touch </li></ul><ul><li>It can be easily printed and we can write on it if necessary </li></ul><ul><li>It is flexible, so we can fold the pages if necessary </li></ul><ul><li>It is not too heavy, so we can carry it wherever we want </li></ul>
  8. 8. <ul><li>A WIRE is made of metal (usually copper), because: </li></ul><ul><li>It is a good conductor of electricity </li></ul><ul><li>It is ductile, so we can make easily wires from this kind of material </li></ul><ul><li>It is flexible, so we can bend it to make an electric circuit </li></ul><ul><li>And they are usually covered by plastic , because: </li></ul><ul><li>It is a good insulator of electricity, so we can avoid short circuits when two wires are together and shocks when we touch them </li></ul><ul><li>A JACKET could be made of fabric because: </li></ul><ul><li>It is a good insulator of heat, so we are warmer when we wear it </li></ul><ul><li>It is flexible, so we can easily put it on and off </li></ul><ul><li>It is not too heavy, so we can carry it on without effort </li></ul><ul><li>It has a good texture, so it is nice to touch </li></ul>

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