Unit 3 Chemistry in Society Plastics and Polymers

1. Unit 3 Chemistry in Society Plastics and Polymers Lots of types were used at the London 2012 Olympics

2. Scenario - Howard was in charge of designing a new toy car for an infant (3-6 years old.) He had the choice of using metal, wood or plastic in his design. Howard decided to use plastic. Why?

3. Properties of Plastics (Polymers) Plastics are used for so many jobs because they have many useful properties. Properties of materials describe what they are like and how they behave. For example, a plastic shampoo bottle has the following properties; Flexible– the shampoo can be squeezed out of the bottle. Watertight – the shampoo will not leak. Shatterproof – the bottle will not break if dropped. Light – this also make it cheaper to transport. Plastics are good heat insulators – this means plastic doesn’t let heat escape. Plastics are also good electrical insulators Plastics can be coloured (any colour) at the manufacture stage unlike metal and wood. Why is plastic used to make shampoo/shower gel bottles?

4. Hydrogels Hydrogels are smart materials. Hydrogels can change structure in response to their environment. Hydrogels are used in nappies and contact lenses (amongst other things)

5. Kevlar Kevlar is an incredibly strong yet lightweight fibre. Kevlar is strong because of its bonding. (higher) Kevlar is used in a range of things including stab vests, motorcycle equipment and now even football boots.

6. Water Soluble Polymers Water soluble polymers are plastics that dissolve in water. In the past high temperatures were needed to dissolve the polymer but advances in recent years means lower temperatures are successful too. Water soluble polymers are used in hospital laundry bags and washing up ‘liquitabs’

8. Advantages and Disadvantages of Plastics Advantages Disadvantages The main advantage plastics is also the reason why plastic is such a problem. It lasts forever. (doesn’t biodegrade) Plastics are reusable. Plastics are usually shatterproof and are see-through. Light-weight and odourless. Burning plastics can be very dangerous as they give off toxic and poisonous fumes. Different plastics give off different types of fumes. All plastics give off carbon monoxide. Made from Crude Oil which is a finite resource. (i.e. it’s running out) Plastics don’t biodegrade (i.e. they don’t break down naturally)

9. Reminder; An addition reaction occurs when something adds across a double bond. During an addition reaction the carbon to carbon double bond is broken.

10. How are Addition Polymers are made? Plastics are made up of huge long chain molecules called polymers. Polymers are made when many small molecules, called monomers, join together. These monomers (usually alkenes) must contain a carbon double bond and join together to form saturated polymers. This process is called addition polymerisation (only carbons bonded together i.e. carbon ‘backbone’)

11. Making poly(ethene) whiteboard example (mono means one, poly means many) Monomer name; ethene Polymer name; poly(ethene) Monomer structure; Polymer structure; Repeating unit;

12. Making poly(propene) whiteboard example Monomer name; propene Polymer name; poly(propene) Monomer structure; Polymer structure; Repeating unit;

13. Making poly(styrene) whiteboard example Monomer name;Polymer name; Monomer structure; Polymer structure; Repeating unit;

14. Reminder; In a condensation reaction two molecules join and a small molecule (often water) is removed. Making an ester is an example of a condensation reaction.

15. How are Condensation Polymers are made? Some examples of condensation polymers are nylon, poly(ester), proteins, starch and cellulose. Poly(ester) and nylon are synthetic (man-made) while the others mentioned above are natural. The monomers used to make condensation polymers have two functional groups at each end of the molecule – they are bifunctional. A small molecule is also produced when a condensation polymer is formed. This process is called condensation polymerisation (other elements as well as carbon are bonded together in the molecule’s ‘backbone’)

16. Making a poly(ester) whiteboard example Carboxylic acid + Alcohol Ester + Water Therefore; ‘Diacid’ + ‘Diol’ Poly(ester) + Water Monomer structures – Polymer structure –

17. Making Starch whiteboard example Starch is a natural condensation polymer made when many glucose monomers join together. Starch, like other natural polymers, are biogradeable (break down/decompose naturally) Monomer structure (glucose) – Polymer structure –

18. Metals

19. Metallic Bonding • Metallic bonding – unsurprisingly – only appears in metal elements. • Metallic bonding occurs between metalions(positively charged) and delocalised outer shell electrons (negative)– opposite attract. • ‘delocalised’ means the electrons are common to all of the ions (not just one atom i.e. they hop from one to another)

21. The main properties of metals Strength – metals that are strong are used to make car bodies, bike frames, ships hulls etc. Malleability (mouldable) – this means that they can be shaped by hammering or rolling and can be bentwithout breaking. For example car chassis. Conduction of electricity–all metal elements conduct electricity. Non metals (except carbon in graphite form) do not. Copper is used in household wires, aluminium wires are used in overhead power lines.

22. Conduction of heat – metals are good conductors of heat. We use metals like aluminium, iron and copper for cooking pots and pans. Density– If we had two pieces of metals the same size, the higher density metal will be heavier than the lower density one. e.g. Lead is highly dense and was useful in old divers suits (i.e. they’d sink!) Aluminium less dense and is used to make planes.

23. Alloys The properties of metals can be changed and improved by making alloys. (i.e. make it stronger or shine more etc. An alloy is a mixture of two or more metals. (in some cases some non-metals are also added) The usual way to make an alloy is to melt together the elements that make it up. Bronze, brass and stainless steel are examples of common everyday alloys.

24. reacts with... extraction method acid water oxygen Lithium Potassium Calcium Sodium Magnesium Aluminium Zinc Iron Nickel Tin Lead Copper Silver Mercury Gold This will act as a summary

25. Ores Unreactive metals such as silver and gold are found uncombined – this is why ‘panning for gold’ can happen. In nature most metals are found in compounds – these compounds are known as ores. Metals can be extracted from their ores in a variety of ways. • Extraction with heat only – gold, silver and mercury. • Extraction with heat + carbon • Extraction with electricity

26. Extraction: Heating with Carbon Some metal ores have to be heated with carbon. This is because the metal ore (usually a metal oxide) needs the carbon to be able to pull the oxygen away from the metal. This leaves the pure uncombined metal. Carbon dioxide is formed too. METAL OXIDE + CARBON METAL + CARBON DIOXIDE

27. Iron and the Blast Furnace iron(III) oxide Stage 3 iron(III) oxide 2 1

28. Extraction of Metals using electricity positive negative More reactive metals (Al and above) are too volatile and therefore dangerous to extract via heat + carbon. Instead we use electricity to attract the ______ metal ion to the _________ electrode.

29. Metal + Oxygen Metal oxide For example; Magnesium + Oxygen Magnesium Oxide All of the metals above __________ in the reactivity series react with oxygen. Metals and Oxygen Important !!! gold

30. Metal + Water Metal Hydroxide + Hydrogen Example; Potassium + Water ____________ + __________ Formula equation: All of the metals above __________ in the reactivity series react with water.(hint - every metal with m at end !!) Metals and Water Important !!! Potassium Hydroxide Hydrogen whiteboard example aluminium

31. Metal + Acid Salt + Hydrogen Example; Zinc + Hydrochloric Acid _________ + _________ Formula equation: All of the metals above _________ in the reactivity series react with acid. Metals and Acid Important !!! Zinc Chloride Hydrogen whiteboard example hydrogen

32. The Reactivity Series A reactivity series of metals is a ‘league table’ which puts the metals in order of how reactive they are. The reactivity series is also known as the electrochemical series. The most reactive metals are at the top and the least reactive are at the bottom.

33. Electrolysis is the splitting (lysis) up of a compound using electricity (electro). Electrolysis Electro lysis

34. Oxidation and Reduction Copper Chloride Example whiteboard example

35. Word bank; atoms, copper, gain, electrons, ions, lose, solution, negative, positive The chlorine ______ (in solution) lose electrons forming chlorine _______. We see these as gas at the ________ electrode. The copper ions (in solution) ______ electrons forming copper atoms. We see these as solid at the _______ electrode. 2Cl- Cl2 + 2e- and Cu2+ + 2e- Cu These are called ion-electron equations. ions atoms positive gain negative

36. OILRIG Oxidation Is Loss (of electrons) Reduction Is Gain (of electrons)

37. whiteboard example In the copper chloride example; Reduction = Oxidation = Ion electron equations are found in the data booklet where they are written as reduction reactions. Reducing agents help reduction to occur by providing electrons.

38. Metals _______ electrons to obtain a full outer electron shell. This makes the metal stable. The electrochemical series is a list of metals arranged in rank order of how easily the metal atoms lose electrons. The electrochemical series in your data booklet Electrochemical Series lose

39. Experiment – Measuring a voltage between two metals. Voltmeter v / other metals A cell can be made when two different metals are connected in contact with an electrolyte. In this cell the electrolyte is sodium chloride. An electrolyte is always an ionic compound and it completes the circuit as it allows the ions flow.

40. When metals ________ their electrons, they do so with a certain force. This force is known as voltage. When twodifferentmetals are connected together in a cell (a battery), the metal with the higher force pushes its electrons on to the other metal. (‘bully rule’) No voltage is obtained when the same metal is connected together. i.e. two pieces of copper metal. lose

41. Important The further apart the metals are in the electrochemical series, the higher the voltage. Electrons flow along the wire from the metal higher in the electrochemical series to the metal lower down.

42. In which direction will electrons flow in the following? A magnesium/iron cell? _____ to _____ through the _____. A silver/aluminium cell? _____ to _____ through the _____. A Cu/Sn cell? _____ to _____ through the _____. wires wires wires

43. Combining Batteries, Oxidation and Reduction Remember the metal higher up in the electrochemical series loses its electrons more easily – i.e. oxidation. Write the ion electron equations and label them reduction / oxidation for the following batteries; • Tin Silver Cell • Magnesium Zinc Cell • Sodium Gold Cell • Lead Iodide Cell

44. REDOX Reactions Oxidation cannot happened without reduction and vice versa. Therefore reactions in electric cells (batteries) can be described as REDOX. Rechargeable batteries and fuel cells are technologies which use REDOX reactions.

45. Writing REDOX equations Zinc Copper Cell OXidation – REDuction – REDOX equation - i.e. the oxidation and reduction equations have been combined and the electrons have been cancelled. whiteboard example

46. Potassium Iodine Cell Oxidation – Reduction – Redox Equation - If the number of the electrons is NOT the same on each side of the equation then you need to multiply the equations to find a common factor. whiteboard example

47. Examples Write the REDOX equations for the following; (show all working please) Magnesium Tin Cell Nickel Chloride Cell Gold Zinc Cell Iron (III) Tin Cell Lithium Aluminium Cell Aluminium Copper Copper Silver Cell Mercury Silver Cell Calcium Bromide Cell Sodium Lead Cell

48. Fertilisers

49. Growth of Plants • To grow well, plants require some essential elements. These are called NUTRIENTS. • Nutrients are made from water soluble compounds. • The most important nutrients that plants require are Nitrogen, Phosphorusand Potassium (often referred to as NPK) • These nutrients are often added in the form of FERTILISERS Why do we use fertilisers?

50. Name + Chemical Formulae of Fertilisers • Ammonium Nitrate (NH4+)(NO3-) • Ammonium Phosphate (NH4+)3(PO43-) • Potassium Nitrate K(NO3-) • Potassium Phosphate K3(PO43-) • i.e. compounds that contain potassium, phosphorus • and/or nitrogen