Using materials

• Describe, in terms of electrons, what happens when a sodium atom reacts with a chlorine atom to produce sodium chloride.

  sodium loses electrons, chlorine gains electrons
• Why do farmers use ammonium nitrate on their fields?

  Fertiliser
• State one reaction condition that can be changed when making poly(ethene)

  Pressure
• Gold and stainless steel are also used for dental braces. Suggest two factors to consider when choosing which metal to use for dental braces.

  Cost

  Strength
• Explain why methane is a gas at 20°C.

  methane has a low boiling point as it has small molecules
• Copper can be extracted from solutions of copper salts by adding iron. Explain why.

  iron is more reactive so copper is displaced
• Describe the structure and bonding in a thermosoftening polymer and explain why thermosoftening polymers melt when heated.

  Large chains with weak intermolecular forces which are easily broken