Chapter 18Polymers LEARNING OUTCOMES Define polymers Distinguish between addition and condensation as reactions in the formation of polymers Show how the monomers are linked in the structure of the polymer Demonstrate the differences in properties between the monomer and the polymer it forms
Chapter 18Polymers LEARNING OUTCOMES Name examples of polymers formed by addition reactions Draw diagrams to represent the formulae of monomers State at least one use of each of the following types of polymers: polyalkene Name examples of polymers formed by condensation reactions Draw diagrams to represent the formulae of compounds State at least one use of each of the following types of polymers: polyamide, polyester and polysaccharide Describe the hydrolysis of proteins Compare acid hydrolysis of a polysaccharide with carbohydrate digestion in the body
Chapter 18PolymersPolymers Polymers are very large molecules called macromolecules. A macromolecule or polymer is built up of many small units called monomers. Different macromolecules or polymers have different units or monomers joined by different linkages. A polymer is a macromolecule which is made up of a large number of simple molecules called monomers. monomer monomer monomer monomer polymer
Chapter 18PolymersClassifying Polymers Polymers are either naturally occurring or synthetic. Polymers are either addition polymers formed by an addition process, or condensation polymers, formed by the condensation process.
Chapter 18PolymersPolymerisation Polymerisation is the process whereby two or more simple molecules (monomers) react and link together to form a much larger molecule called polymer. There two types of polymerisation: Addition polymerisation and Condensation polymerisation.
Chapter 18 PolymersAddition polymerisation In addition polymerisation one monomer adds on to the another monomer to form a long chain polymer. The monomers must have a carbon-carbon double bond so that addition reaction can take place.
Chapter 18PolymersExample of addition polymerisationFormation of polyethene from ethene
Chapter 18PolymersUses of polyethene Polyethene is the most widely used form of plastics. It is used for making common household items like: plastic bags plastic bottles and containers clingfilm for wrapping fish and vegetables plastic buckets and hoses
Chapter 18PolymersOther addition polymers and their usesPoly Vinyl Chloride (PVC) It is an addition polymer made from a monomer called vinylchloride or chloroethene. It is used for making water pipes, gloves, rain coats andshower curtains.
Chapter 18PolymersOther addition polymers and their usesPoly(tetrafluoroethene) [PTFE] It is an addition polymer made from a monomer calledtetrafluoroethene. F F C=C F F It is used for making seals and washers and for coatingnon-stick pots and pans.
Chapter 18PolymersCondensation Polymerisation In condensation polymerisation, two or more monomers join together with the elimination of a small molecule, such as water. The monomers must have different reactive functional groups so that they can react together to form a polymer. The polymer formed is called a condensation polymer.
Chapter 18PolymersExample of condensation polymerisation:Nylon Nylon is formed by condensation polymerisation from a dicarboxylic acid (hexanedioic acid) and a diamine (1,6-diamino-hexane). Uses of nlyon:
Chapter 18 Polymers Terylene Terylene is also a condensation polymer. Terylene is formed by condensation polymerisation from an diacid (benzene- 1,4-dicarboxylic acid) and a diol (ethane- 1,2-diol). = O It is a polyester with a –C–O– linkage. Uses of terylene:
Chapter 18 Polymers Fats and Oils Fats and oils are polyesters. A fat molecule consists of two parts – glycerol and chains of fatty acids. Fats and oils contain three ester functional groups. When fat is hydrolysed by an enzyme such as lipase, glycerol and fatty acids are produced.
Chapter 18PolymersTest for Fats1. Add 2 cm3 of ethanol to a sample of the unknown in a test tube.2. Shake the mixture thoroughly.3. Add 2 cm3 of water.If fat is present, a cloudy white suspension will form at the top of the solution.
Chapter 18PolymersPolysaccharides Polysaccharides are naturally occurring compounds with a general formula CnH2nOn. ‘Mono’ means one and ‘saccharide’ means sugar. Monosacharides are simple, single sugar molecules which comprise only one single basic unit. E.g. glucose, fructose, galactose Diasaccharides are complex sugars made up of two simple sugar molecules. They are formed by condensation reactions. E.g. sucrose, lactose, maltose Polysaccharides are made up of a large number of monosaccharides joined together by numerous condensation reactions. E.g. starch, glycogen, cellulose
Chapter 18PolymersTest for Starch1.Add a few drops of iodine solution to the unknown substance.2.Observe the colour change, if any.If starch is present, the iodine solution will turn from brown to blue-black.
Chapter 18 Polymers Test for Reducing Sugars – Benedict’s Test1. Add 2 cm3 of Benedict’s solution to 2 cm3 of glucose solution or any other food solution to be tested.2. Shake the mixture and immerse the test tube in a beaker of boiling water for two minutes.3. Observe and record any changes in colour. If reducing sugar is present, a brick red ppt. (or green, yellow, or orange ppt.) is formed. If no reducing sugar is present, the solution remains blue in colour.
Chapter 18PolymersPlastics Plastics are one of the most common materials used in the world today. It has wide applications in making a host of things ranging from spectacles to aeroplane parts. There are many kinds of plastics, such as: Polyethene Nylon PVC Polystyrene
Chapter 18PolymersProperties of plasticsAdvantages Light and durable Corrosion resistant Can be easily moulded into a wide variety of shapes and sizes Relatively cheap
Chapter 18PolymersProperties of plasticsDisadvantagesThey burn easily to produce toxic fumes. Most plastics are non-biodegradable, (cannot be decomposed by air and bacteria), and hence causes pollution to the environment. They are not as strong as metals.
Chapter 18PolymersProblems caused by the use of plastics The use of plastics in society has increased at a tremendous rate. We use twenty times more plastic than we did fifty years ago. The manufacture of plastics uses up about 8% of the world’s oil supply, leading to more competition for petroleum. Since most plastics are non-biodegradable, the amount of plastic waste accumulating is rapidly increasing in our environment. Discarded plastics in rivers and oceans cause the death of many sea creatures like turtles, fish and whales.
Chapter 18PolymersSome ways to reduce pollutioncaused by plastics1. Reduce the use of plastics for packaging and transportation of goods.2. Reduce the use of takeaway plastic bags when you shop at supermarkets.3. Practise and promote the use of proper disposal of plastics used at home and on the beaches.4. Reuse and recycle the used plastics.
Chapter 18PolymersQuick check1. What is a polymer? Give two examples of polymers.2. (a) State two reasons for using plastics in place of metals. (b) Why is the body of a motor car not entirely made of plastics?3. (a) What is the difference between addition polymerisation and condensation polymerisation? (b) Give two examples each of addition polymers and condensation polymers.4. Deduce the structure of the monomers from which the following polymers are built from.(a) (b) Solution
Chapter 18PolymersSolution to Quick Check1. A polymer is a macromolecule made up of many small units called monomers, e.g. nylon & Terylene.2. (a) Plastics are lighter and easier to mould. (b) Plastics are not strong enough to protect the occupants in the car in case of accidents.3. (a) In addition polymerisation, monomers are added one to another to form a polymer, without any molecule being removed from the reaction. In condensation polymerisation, monomers are joined together with the elimination of a small molecule, such as water. (b) Addition polymers: polyethene, polypropene Condensation polymers: nylon, Terylene.4. (a) (b) Return
Chapter 18Polymers To learn more about Macromolecules and Plastics, click on the links below! 1. http://en.wikipedia.org/wiki/Polymer 2. http://www.chemheritage.org/EducationalServices/nylon/chem/chem.html 3. http://www.chemguide.co.uk/organicprops/esters/polyesters.html 4. http://www.plasticsresource.com/s_plasticsresource/index.asp 5. http://www.sdplastics.com/plastics.html