C4: Material Choices

C4: Material Choices

1. Polymers

   • Long molecules formed when small molecules (monomers) join together, which is call polymerisation. Can occur naturally or synthetically.
   • Held Together by Covalent Bonds
     • In between the covalent bonds, there are intermolecular forces, which are stronger and harder to break so most polymers are solid. The forces are still weaker than ionic or covalent bonds, so polymers have lower melting points.

2. Giant Covalent Structures

   • Don't conduct electricity
   • Insoluble in water
   • Diamond
     • The 4 covalent bonds that forms a carbon atom is very rigid which makes diamond really hard.
     • Takes a lot of energy to break so gives diamond a very high melting point.
     • Doesn't conduct electricity because it has no free electrons
   • Graphite
     • Each carbon atom only forms 3 covalent bonds, so the sheets of carbon atoms are free to slide over each other.
     • A high melting point
     • Conducts electricity because there a lot of electrons that can move.

3. Nanoparticles

   • Very small particles which are given in nanometers - 1nm = 0.000000001m = 1 x 10-9m.
   • Large surface area

4. Bulk Properties of Materials

   • Different Materials Have Different Properties
     • Melting point
     • Strength
     • Stiffness, Brittleness, Hardness
     • Conductivity
     • Ease of reshaping

5. Types of Materials

   • Ceramics
     • Made by baking substances E.G:
       • Clay
         • Is soft when it's wet - easy to mould into different shapes. Hardened by firing at very high temperatures.
   • Can be Damaged by Corrosion

6. Materials and Their Uses

   • Different Materials = Different Jobs
     • Polymers - Easily adaptable, flexible, easily moulded, cheaper than most materials, less dense - Used to design products that need to have a low mass.
     • Ceramics - Insulators of heat & electricity, won't corrode like other materials can, last longer.
     • Metals - High melting points, conductors of heat & electricity, malleable (can be formed in other shapes).