C2 - Material Choices

C2 - Material Choices

1. Natural and Synthetic materials

   • All materials are made of chemicals
     • Made from atoms or groups of atoms (molecules)
   • natural
     • Materials from plants
       • Wood and paper from trees
       • Cotton from cotton plant
     • From anilmals
       • Wool from sheep
       • Silk from silkworm larvae
       • Leather from cows
   • Synthetic - made by humans
     • can control porperties
       • Rubber altered in a factory
       • Nylon and Polyester for clothes
         • Waterproofing, stretchy, sparkly
       • Paints
     • Raw materials used to make synthetic materials come from the Earth's crust

2. Materials and Properties

   • Melting and boiling points
     • The temperature at which a: solid turns to liquid or a liquid turns to gas
   • Strength
     • The ability to resist a force before breakage or deformation
       • Tensile
         • Pulling force
           • Ropes and cables
       • Compressive
         • Pushing force
           • Concrete for construction
   • Stiffness
     • Inflexibility
   • Hardness
     • Difficulty to cut into a material
       • Hard = Diamond
         • Hardest naturally occuring material
       • Soft = Paper
   • Density
     • Materials mass per unit volume
       • eg. g/cm3
     • Buoyancy
       • Objects which are less dense than water will float
       • Objects which are more dense than water will sink.

3. Material's Properties and Uses

   • Uses for materials depend on the material's properties
     • Examples
       • Plastics
         • Hard, Strong and Stiff
         • Low density (lightweight)
         • Mouldable
         • Cases for TVs, Computers and Kettles
       • Rubber
         • Strong
         • Mouldable
         • Car Tyres
       • Nylon Fibres
         • Soft and Flexible
         • Good tensile strength
         • Ropes and Clothing
   • Properties of a product depend on the materials
   • Suitablity of material for use
     • Cooking utensils
       • Non toxix, high melting point
     • Toy car
       • non toxic, strong, stiff and low density

4. Nanotechology

   • Nanomaterials are tiny
     • 1nm = 0.000 000 001m
     • 1-100 nanometres across are nanoparticles
     • Natural
       • Sea-spray
       • Combustion produces nano particulates
     • Different properties than larger particles of the same chemical
       • Sliver cant kill bacteria due to its lower surface area to volume ratio
   • Branch of technology dealing with nanoparticles
     • Design nanomaterials for specific uses
       • Strengthening sports materials such as tennis rackets, golf clubs and golf balls.
       • Silver particles in surgical masks and plasters giving antibacterial properties
   • Ethics
     • Effects of nanoparticles are unknown
       • Testing is important
       • Long term risks cannot be tested
         • Clearly labled so that consumers can choose to use or not use

5. A