C2

Seite 1

Natural & Synthetic Materials

1. Natural materials come from living things e.g. cotton, paper, wool, silk

2. Synthetic materials are produced by chemical synthesis from materials from the Earth's crust e.g. crude oil used to produce fuels

Fractional Distillation

Way of separating hydrocarbons in crude oil by heating it.

1. The tower is hotter at the bottom and the temperature decreases as the evaporated crude oil travels up it.

2. When a particular hydrocarbon gets to the point in the tower where it's boiling point is, it will condense and run out of the tower where it is collected and can be used for its suited purpose.

3. Any remaining gases leave the tower at the top and can be used as gaseous fuels.

Boiling Point

Molecules are held together by intermolecular forces. The longer the molecule, stronger the forces are therefore a higher amount of energy is required to break the bond which makes the boiling point higher.

Properties of Materials

Soft - easily dented & scratched, malleable

Hard - not dented or scratched easily, not mouldable or bendy

Flexible - bends easily

Rigid - does not change shape easily

Dense - does not scratch easily, compacted substance

Strong - does not break when stretched

Weak - breaks easily when pulled or stretched

Polymerisation

Polymers are a chain of hydrocarbon monomers e.g. poly-ethane is a chain of ethane monomers. Different monomers make different polymers.

Polymerisation is the chemical process of turning monomers into polymers. It can be done to create a wide range of materials with different properties so that they have different purposes.

Traditional materials have been replaced with polymers so that they are more practical e.g. paper bags are now plastic (polythane) because it is stronger and waterproof. Window frames that were wood are now made of uPVC because it doesn't rot.

POLYMER CHAIN

Molecular Structure of Materials

A material's properties depend on how it's particles are arranged.

Weak forces between molecules allow it to be flexible and have low melting points. Materials can be strengthened by using cross-links which stop the polymer molecules from moving to make it hard and rigid.

Plasticizers are used to make a material soft and flexible by forcing the chains apart and therefore making the force between them weaker.

Polymers can also be modified by packing the molecules more closely which forms a crystalline polymer. This make the material stronger and denser with a higher melting point.

PLASTICIZERS

CROSS-LINKS

Nanotechnology

Nanoparticles are used to modify the properties of materials (polymers):

1. Silver nanoparticles have antibacterial properties and stop socks from smelling.

2. Adding carbon nanotubes to tennis rackets makes them lighter, stronger and stiffer.

New Page