Topic 24 - Polymers Flashcards
9.17C - What is a polymer?
A large molecule made from a lot of small molecules called monomers.
It is a substance of high average relative molecular mass made up of small repeating units.
9.18C - How are molecules joined together in a condensation reaction to form poly-ethene?
Polythene is a polymer formed when a large number of ethene molecules are joined together.
Ethene molecules have a double covalent bond between carbon atoms.
One of the bonds in the double bond break and another ethene molecule joins.
This process repeats itself, forming a long chain, this is addition polymerisation.
Repeating units show how an individual monomer changes across a chain with brackets.
Structural formulae shows a group of monomers with single bonds.
9.19C - How are addition polymers made by combining monomers like poly(chloroethene)?
Poly(chloroethene) is formed when chloroethene monomers undergo addition polymerisation.
9.20C - How do you deduce the structure of a monomer from its polymer and vice-versa?
To work out the structure of the monomer from the polymer, remove the brackets and the extended bond lines.
Draw double bonds between carbon atoms
9.21C - Explain how the uses of polymers link to their structures
Polyethene is flexible, cheap and a good insulator
It can be used for plastic bags, bottles and electrical wire coating.
Polypropene is flexible and strong. It is used for buckets and crates.
Polychloroethene/PVC is tough, cheap and long lasting. It is used in window frames.
PTFE is tough and non stick. It is used no stick coating in pans.
9.22C - What is condensation polymerisation?
Where an ester and water are formed from a carboxylic acid and an alcohol.
In condensation polymerisation, polyesters which are synthetic polymers made by monomers join together and eliminate a small molecule like water.
These polyesters can be used in plastic bottles to make them strong, lightweight and recyclable.
9.22C - Which two functional groups react to form a polyester?
A functional group is an atom or group of atoms responsible for the properties and reactions of the compound.
Alcohol has a functional group of -OH
Carboxylic acids have a functional group of -COOH.
Esters have the functional group -COO. It is represented with a double bond and single bond from the carbon to either oxygen.
9.22C - How are esters formed?
When a carboxylic acid and an alcohol reacts, with a catalyst, it produces an ester and water.
For example, ethanoic acid reacts with ethanol to form and ester ( ethyl ethanoate ) and water. Polyesters contains many ester links and the monomers that form the polyester contain a carboxylic acid and alcohol.
To form a long chain, the polyester has to have a two functional groups, with one at each end of the chain.
The -OH and H at the end of the chains are eliminated, to form water.
9.22C - What are the uses of polyesters?
Polyesters can be used in the manufacturing of synthetic fibres for clothes.
One form of polyester is a polyamide.
9.23C - Describe some problems associated with the making of polymers
Polymers are made from crude oil, fractional distillation further cracks the oil to produce useful chemicals.
Most of the monomers needed to make synthetic polymers are obtained from crude oil.
This is a finite resource and is non-renewable so monomers need new sources in the future.
9.23C - Describe some problems associated with the disposal of polymers
Materials like wood and paper are biodegradable as they can be broken down,
Most synthetic polymers are useful as they aren’t biodegradable so lasts for a long time.
Most plastic rubbish goes landfill sites.
So some waste is incinerated and the energy can generate electricity. However, all plastics produce CO2, greenhouse gases and toxic substances when burnt.
Although these toxic substances can be removed, it forms toxic ash that should be dealt with carefully.
Amount of waste can be minimized by reusing and recycling plastics, this helps conserve crude oil supplies.
9.24C - Evaluate the advantages and disadvantages of recycling polymers
The recycling of plastics are difficult as it takes some steps:
Collect the waste - Kerbside collection or people taking it to a collection point.
Sort the waste into different polymers - Done by hand, so time-consuming.
Dispose of waste unable to be recycled in landfill sites.
Clean polymers, grind into chippings, purify chippings.
Melt chippings to produce a new product.
To make polymer sorting easier there are symbols on plastics to show this.
9.25C - What are some naturally occurring polymers?
DNA is made of four different monomers called nucleotides.
Starch is a polymer made from a strand of sugars called glucose.
Proteins are polymers made from amino acids.
