Polymers and properties of materials

• How are polymers formed?

  When lots of small molecules called monomers join together
• What is the name of the reaction when polymers are formed?

  Polymerisation; it usually needs high pressure and a catalyst
• Plastics are polymers. What are they usually based?

  Plastics tend to be carbon based and their monomers are often alkenes
• Forces between molecules determines the properties of the polymers
• Which bonds hold together the atoms in polymer chains?

  Strong covalent bonds
• What happens to the chains if the plastic made up of chains that are held together by weak intermolecular forces?

  The chains will be free to slide over each other; the plastic can be stretched easilly, and will have a low melting point
• Some plastics have stronger bonds between the polymer chains. Why is this?

  (These may be covalent bonds - sometimes called cross-links) These plastics have higher melting points, are rigid and can't be stretched, as the cross-links hold the chains firmly together
• What do all the different types of materials have in common

  The fact that their properties all depend of the structure and bonding in the material
• What actually determines the properties of a material

  The type and the strength of the bonds in a material - not the individual atoms themselves
• Why are the ionic bonds in sodium chloride really strong

  Due to the strong electrostatic attraction between the ions, which acts in all directions within the lattice structure
• The determines the high melting and boiling points

  The strength of the bonds
• What is chloromethane and why does it have a low meltin and boiling point

  It's a simple molecular substance - the covalent bonds that hold the atoms in each molecule are very strong but the intermolecular forces attracting the molecules to each other are weak and easily overcome
• Why jd polyvinl chloride strong and rigid

  The intermolecular forces between the polymer chain in PVC are relatively strong