Polymers

Polymers- NEEDS SEVERE PRACTICE

Large molecules made up of chains of repeated units of smaller identicle molecules called monomers.

Monomers 

Monomers make up a polymer- chains of monomers make up a polymer.

Properties of a polymer

Hard wearing, flexible, waterproof, strong , unreactive, insulator

Natrual polymers

Examples of natrual polymers:

Protein (amino acids are the monomers, they make up the protein)

Natrual Rubber monomer is isoprene

DNA 

Starch (glucose is the monomer, they make up starch which is the polymer)

Lipids, monomer is fatty acids and glycerol

Synthetic polymemrs: Uses and Properties

Made in laborities mainly using crude oil.

Properties: Flexible, waterproof, good insulators, tough, long-lasting, hard, slippery, non-stick, flexible forms.

Poly(propene), (polypropylene): Used for buckets, washing up bowls, climbing ropes and strorage crates.

Poly(chlorethene) (PVC): Used for window and door frames, gutters, drainpipes, and insulation for electrical wires.

Poly (tetrafluorethene) (Teflon): Used for coats, non-stick pans, skis, stain-proof clothes and carpets.

Poly(ethene) (polythene): Used for cling film, plastic bags, drink bottles, paddling pools, polytunnles.

Polymerisation

When monomers form polymers, this reaction is an exothermic reaction

Exothermic vs Endothermic

Exothermic: Releases more energy into the surroundings than it takes inand makes the environment warmer.

Endothermic: Takes in more energy into the surrounding than it releases and makes the environment cooler.

E.g: Photosynthises- Carbon Dioxide+Water—> Glucose+Oxygen

Rubber

• It is a type of natrual polymer. And its monomer is isoprene

• Properties: When hot, it is soft and sticky, glue. When cold it is hard and brittle. 

• Vulcanisation: This can change the properties of rubber. First, rubber is heated with sulphur, then a reaction takes place, cross links will form between the long molecules (rubber), the cross links makes the rubber much harder and tougher plus it stops its properties from changing with temperature.

• Vulcanised rubber is more elastic than natrual rubber because it has cross links that prevents layers from sliding past each other

Plastic vs Elastic

A material that keeps its shape is said to be plastic.

A material that goes back to its original shape when the streaching force is removed is said to be elastic. They have an elastic limit, if they are streached past that limit, it won’t go back to its original shape.