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Comparing material properties

Material Properties

  • Melting point- temperature at which a solid turns into a liquid
  • Tensile strength- the force needed to break a material when it is being stretched
  • Compressive strength- force needed to crush a material when it is being squeezed
  • Stiffness- the force needed to bend a material
  • Hardness- how well a material stands to wear
  • Density- the mass of a given volume of a material
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Natural and Synthetic Materials

  • Metals- shiny, malleable, and electrical conductors
  • Ceramics- clay, glass, and cement. hard and strong
  • Polymers- large molecules used to make rubbers, plastics, and fibres
  • Natural Materials- cotton and paper, from plants and silk and wool from animals
  • Synthetic Materials- manufactured by chemical reactions using raw materials
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Crude Oil

  • Crude oil is a mixture of thousands of hydrocarbons
  • nearly 90% of crude oil is used as fuels
  • around 3% of crude oil is used to synthesis other chemicals 

Fractional Distillation-

  • the oil is heated up which turns it into all gases
  • the distillation tower is cooler at the top
  • gas molecules condense into liquids when they cool
  • liquids with similar boiling points collect together, we call these fractions
  • hydrocarbons in each fraction have boiling points within a range of temperatures
  • molecule chain lengths are similar sizes within each fraction
  • the smaller the molecule chain length, the lower the boiling point
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Making Polymers

  • a polymer is a large molecule made by joining many smaller molecules called monomers
  • a polymer is made by a process called polymerisation
  • small forces attract molecules to eachother
  • the forces are strongest when molecules are close together
  • the stronger the force the more energy is needed to seperate the molecules
  • low density polyethene has long molecules with branches, the branches keep molecule chains apart so the forces between different molecules are weak
  • high density polyethene has long chains but no branches, so the molecules are close together and it is much stronger
  • high crystalline polymers are strong with high melting points but can be brittle
  • longer chains need more force to seperate them
  • plasticisers are used to make polymer softer, and weaken the forces between molecules
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Nanoparticles

  • nanotechnology is the use and control of very small structures
  • a nanometre is one millionth of a millimetre
  • nanoparticles have high surface area so are more reactive
  • they range in size from 1nm-100nm
  • silver nanoparticles are good at killing bacteria
  • titanium oxide nanoparticles are put into sunscreen 
  • if silver nanoparticles are released into the environment they could kill lots of useful micro organisms
  • the effects of nanoparticles are not yet known
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