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Chapter 23: Polymers and Alcohols

23.1-Addition Polymers

Polymers

  • Polymers are long molecules made up of hundreds or thousands of repeating subunits.

  • They are really useful materials for everyday items, such as plastic containers and clothing, but they are a nuisance when it comes to throwing them away because they aren’t broken down easily.

Addition Polymerisation

  • Addition polymers are formed by joining lots of alkene molecules together.

  • The single alkene is called a monomer and when several monomers are connected together, we call this a polymer.

  • Polymerisation happens when the double carbon bond breaks, allowing another alkene to connect to the carbon.

  • This happens multiple times until you end up with a polymer made up of hundreds or thousands of monomers.

    • Instead of drawing out a really long chain, it’s much easier to represent polymers by drawing a single subunit (the monomer) inside square brackets, with a little ‘n’ in the right hand corner to show that we have lots of them joined together.

      • Remember to draw bonds sticking outside the square brackets to make it clear that the chain continues.

  • We name the polymer depending on the type of monomer it is made from and stick the word poly at the front.

    • Let’s say we have a polymer made up of lots of ethene molecules joined together - this would be called poly(ethene), which we also refer to as polythene.

    • Polythene is everywhere - you’ll find it in things like plastic water bottles, bin liners and hose pipes.

23.2-Alcohols

Alcohols

  • Functional Groups

    • The ‘O-H’ bond is the functional group of alcohols. Alcohols contain a bond between O-H, where the oxygen is bonded to a carbon. This is their functional group, used in reactions.

    • As we have seen with alkanes and alkenes, alcohols can also be named. The first four alcohols in the homologous series are called methanol, ethanol, propanol and butanol.

Representing Alcohols

  • Alcohols can be represented. We can represent alkenes very easily,  by using the number of carbons each molecule contains. Ethanol can be represented as CH3CH2OH.

  • Alcohols can be drawn out. We can also represent alcohols using their displayed formulae. For example, the displayed formulae of ethanol is shown below.

Production of Ethanol by Fermentation

  • Ethanol (C2H5OH) is one of the most important alcohols

  • It is the type of alcohol found in alcoholic drinks such as wine and beer

  • It is also used as fuel for cars and as a solvent

  • It can be produced by fermentation where sugar or starch is dissolved in water and yeast is added

  • The mixture is then fermented between 15 and 35°C with the absence of oxygen for a few days

  • Yeast contains enzymes that break down sugar to glucose

  • If the temperature is too low the reaction rate will be too slow and if it is too high the enzymes will become denatured

  • The yeast respire anaerobically using the glucose to form ethanol and carbon dioxide:

Practice Questions:

  • Give an example of an alkene polymer.

    • Polythene/propene/butene

  • How are polymers made?

    • Monomers join together by polymerisation

  • Define condensation polymerisation.

    • Condensation polymerisation involves monomers with two functional groups

    • When these monomers react they join together usually lo sing small molecules, so are called condensation polymerisation reactions

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Chapter 23: Polymers and Alcohols

23.1-Addition Polymers

Polymers

  • Polymers are long molecules made up of hundreds or thousands of repeating subunits.

  • They are really useful materials for everyday items, such as plastic containers and clothing, but they are a nuisance when it comes to throwing them away because they aren’t broken down easily.

Addition Polymerisation

  • Addition polymers are formed by joining lots of alkene molecules together.

  • The single alkene is called a monomer and when several monomers are connected together, we call this a polymer.

  • Polymerisation happens when the double carbon bond breaks, allowing another alkene to connect to the carbon.

  • This happens multiple times until you end up with a polymer made up of hundreds or thousands of monomers.

    • Instead of drawing out a really long chain, it’s much easier to represent polymers by drawing a single subunit (the monomer) inside square brackets, with a little ‘n’ in the right hand corner to show that we have lots of them joined together.

      • Remember to draw bonds sticking outside the square brackets to make it clear that the chain continues.

  • We name the polymer depending on the type of monomer it is made from and stick the word poly at the front.

    • Let’s say we have a polymer made up of lots of ethene molecules joined together - this would be called poly(ethene), which we also refer to as polythene.

    • Polythene is everywhere - you’ll find it in things like plastic water bottles, bin liners and hose pipes.

23.2-Alcohols

Alcohols

  • Functional Groups

    • The ‘O-H’ bond is the functional group of alcohols. Alcohols contain a bond between O-H, where the oxygen is bonded to a carbon. This is their functional group, used in reactions.

    • As we have seen with alkanes and alkenes, alcohols can also be named. The first four alcohols in the homologous series are called methanol, ethanol, propanol and butanol.

Representing Alcohols

  • Alcohols can be represented. We can represent alkenes very easily,  by using the number of carbons each molecule contains. Ethanol can be represented as CH3CH2OH.

  • Alcohols can be drawn out. We can also represent alcohols using their displayed formulae. For example, the displayed formulae of ethanol is shown below.

Production of Ethanol by Fermentation

  • Ethanol (C2H5OH) is one of the most important alcohols

  • It is the type of alcohol found in alcoholic drinks such as wine and beer

  • It is also used as fuel for cars and as a solvent

  • It can be produced by fermentation where sugar or starch is dissolved in water and yeast is added

  • The mixture is then fermented between 15 and 35°C with the absence of oxygen for a few days

  • Yeast contains enzymes that break down sugar to glucose

  • If the temperature is too low the reaction rate will be too slow and if it is too high the enzymes will become denatured

  • The yeast respire anaerobically using the glucose to form ethanol and carbon dioxide:

Practice Questions:

  • Give an example of an alkene polymer.

    • Polythene/propene/butene

  • How are polymers made?

    • Monomers join together by polymerisation

  • Define condensation polymerisation.

    • Condensation polymerisation involves monomers with two functional groups

    • When these monomers react they join together usually lo sing small molecules, so are called condensation polymerisation reactions