SC24 Flashcards
SC24a
1) Recall the meaning of the term polymer.
2) Describe how ethene molecules join together to form poly(ethene).
1) A polymer is a large molecule made from lots of small molecules, called monomers, joined together.
2) Poly(ethene), more commonly known as polythene, is a polymer formed when a large number of ethene monomers join together. Ethene molecules have a double covalent bond between the carbon atoms. One of the bonds in the double bond breaks open and another ethene molecule adds on. This process happens again and again, forming a long chain. The process in which monomers add together in this way is called addition polymerisation.
SC24a
1) Describe how alkenes undergo addition polymerisation.
2) Explain what starch, DNA and protein are
1) In addition polymerisation, the double bond in a monomer breaks. The monomers link together, and they form a long chain of alkene molecules, called a polymer.
2) DNA is a polymer made from four different monomers called nucleotides. Starch is a polymer made from sugars called glucose. Proteins are polymers made from amino acids.
SC24d
1) State the starting material for most synthetic polymers.
2) Describe the problems associated with the production and disposal of synthetic polymers.
1) Most of the monomers needed to make synthetic polymers are obtained from crude oil.
2) Crude oil is a finite resource and is non-renewable.
Landfill
* Waste polymers are disposed of in landfill sites but this takes up valuable land, as polymers are non-biodegradable so micro-organisms such as decomposers cannot break them down
* This causes sites to quickly fill up
Incineration
* Polymers release a lot of heat energy when they burn and produces carbon dioxide which is a greenhouse gas that contributes to climate change
* Polymers that contain chlorine such as PVC release toxic hydrogen chloride gas when burned
* If incinerated by incomplete combustion, carbon monoxide will be produced which is a toxic gas
SC24d
1) Describe some advantages of recycling polymers (state 4).
2) Describe some disadvantages of recycling polymers (state 5).
1) Short version: decreases crude oil use; reduces toxic gas emissions; reduces landfill sites needed; provides employment.
Long version:
* Recycling decreases the use of crude oil which allows it to be kept for other purposes
* It is better for the environment as plastic waste is being collected and reused, hence recycling reduces the emissions of greenhouse gases and other toxic gases produced during the manufacturing process
* It also reduces the amount of landfill sites needed
* Recycling is itself an entire industry which creates employment and economic growth
2) Short version: sorting polymers is tedious and costly; not enough starting ingredients to make new polymers; melting polymers produces toxic gases; can only be recycled a limited number of times; risk of mixing different materials, which can affect its properties.
Long version:
* Sorting plastics by type of polymer is a tedious and labour intensive process which is costly
* Recycling counts on what is collected in as the raw material, therefore production of certain types of polymers may not be possible due to a lack of starting ingredients
* Melting polymers produces toxic gases that are harmful to plants and animals
* Polymers can only be recycled a number of times before they lose their properties and become useless
* Recycling runs the risk of mixing different polymers together, which again will affect their properties. This is particularly risky for polymers designed for specialist use such as aircraft or automobile parts, where safety is of utmost importance
SC24b
1) Describe how other addition polymers are formed from their monomers: poly(propene), poly(chloroethene) (PVC) and poly(tetrafluoroethene) (PTFE).
2) Deduce the structure of a polymer from the structure of a monomer.
1) Addition polymers are formed from their monomers where alkene molecules undergo addition polymerisation. This works because alkene molecules a have a carbon-carbon double bond. The section inside the bracket is the monomer that the polymer was made from. For example, for PVC, chloroethene is the monomer.
2) To deduce the structure of a polymer from the monomer:
Draw the structure of the monomer but use C–C instead of C=C.
Draw brackets around the structure with a long bond passing through each one.
SC24b
1) Deduce the structure of a monomer from the structure of a polymer.
2) Explain how the uses of a polymer are related to its properties: poly(ethene), poly(propene), poly(chloroethene), Poly(tetrafluroethene).
1) You can work out the structure of a monomer from the formula of the polymer. Remove the brackets and the extension bond lines that go through them, and then draw a double bond between the two carbon atoms. Keep all the other atoms or group of atoms the same.
2) Poly(ethene)/ polythene is flexible, cheap and a good insulator. Therefore, it is used in plastic bags, plastic bottles, cling film and polytunnels.
Poly(propene)/ polypropylene is flexible and does not shatter. Therefore, it is used in buckets and bowls, crates, ropes and carpets.
Poly(chloroethene)/ PVC is tough, a good insulator, and can be made hard or flexible. It is used in window frames, gutters, pipes, and insulation for electrical wires.
Poly(tetrafluroethene)/ PTFE is tough and slippery, so it’s used in non-stick coatings for frying pans and kitchen utensils, burette taps, stain-proofing clothing and carpets.
SC24c
1) Explain what is meant by a condensation reaction.
2) Draw the structure of a molecule with two carboxylic acid groups.
3) Draw the structure of a molecule with two alcohol groups.
1) A condensation reaction is where the monomers join together and eliminate a small molecule, such as water.
2) A monomer with two carboxylic acid groups would have two carbons with an oxygen double bond each, and an OH each.
3) A monomer with two alcohol groups would have two carbons with two hydrogens attached to each, and then an OH attached to each.
SC24c
1) Draw the structure of a polyester.
2) Explain how a molecule of water is formed each time an ester link is formed.
1) The carboxylic acid loses an OH, and the alcohol loses a H. The O from the alcohol them links to the C in the carboxylic acid that is attached to the O by a double bond. The carboxylic acid also loses the OH at the other end, which is replaced with a bond line going outside the brackets, and the alcohol loses a hydrogen, which is replaced with a bond line.
2) An -OH from a carboxylic acid monomer combines with a hydrogen atom lost from an alcohol monomer.
