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2. The units in this module are: C2a – Paints and Pigments C2b – Construction Materials C2c – Does the Earth move? C2d – Metals and Alloys C2e – Cars for Scrap C2f – Clean Air C2g – Faster or Slower 1 C2h – Faster or Slower 2 Click on the links to take to the topic you wish to revise. Next page

3. What’s in a paint? How paints dry What is a colloid? Thermochromic paints Phosphorescent paints Main menu Download podcast here Next page

4. What’s in a paint? Main menu Back to C2a ingredients Paints have different ingredients in them to do different jobs Reason PigmentTo provide colour Binding agentKeeps the paint attached to the surface solventDissolves the pigment and binding agent Next page

5. How paints dry Main menu Back to C2a Water based solvent evaporates Water based paints such as emulsion paints dry because the solvent evaporates and forms a film Oil basedsolvent evaporates oxygen Oil based paints dry because the solvent evaporates and the binding agent reacts with oxygen and harden to form a film of paint Next page

6. What is a Colloid? Main menu Back to C2a colloid Paint is a mixture called a colloid solid liquid do not dissolve A colloid is where solid particles are mixed with liquid particles but do not dissolve. dispersed The solid particles are dispersed in the liquid. They are so small that they do not settle on the bottom and stay mixed. Next page

7. Thermochromic paints Main menu Back to C2a special There are some special types of paints available. pigments temperature Some paints contain pigments that change colour as temperature changes thermochromic These are called thermochromic paints Uses of these paints include: thermometers cups kettles baby spoons eggs Next page

8. Phosphorescent paints Main menu Back to C2a glow in the dark Some paints can glow in the dark. phosphorescent pigments They contain phosphorescent pigments. light These pigments absorb and store light energy. Uses : dash boards warning signs radioactive watch faces Before phosphorescent pigment were used, radioactive materials were used on watch faces to make them glow Next page

9. For a paint you need a pigment Blend the powder with an oil Thin it with a little solvent Stir it well but do not boil Paint it on, this is your colloid Let the solvent blow away It’s the same with an emulsion Of two liquids, one will stay Left behind the binding medium Sticks the colour to the wall Forms a smooth protective layer Doesn’t look too bad at all Dyes and paints can make a statement Dress up as a ghost or sprite Use some paint that’s phosphorescent Lit by day, it glows by night Choose a colour that’s synthetic If you want to paint the town Or wear the latest thermochromic Heat – or cold – will change it round

10. Click here to take you to a quiz on “Paints and Pigments” Main menu Back to C2a Next page

11. Which materials are used? Products from rocks Using limestone Making concrete Problems with rocks Main menu Download podcast here Next page

12. Which materials are used? Main menu Back to C2b materials Lots of materials can be used in buildings Some examples are : glass bricks steel aluminium wood iron Next page

13. Products from rocks Main menu Back to C2b Limestone, granite and marble Limestone, granite and marble are three rocks which can be used as construction materials. Limestone Sedimentary rock Made by sea creatures sinking to the bottom of the sea and buried Granite Igneous rock Formed when molten rock cools down Marble Metamorphic rock Made by action of heat and pressure on limestone Next page

14. Heating limestone Main menu Back to C2b calcium carbonate, CaCO 3 Limestone is calcium carbonate, CaCO 3 thermal decomposition Heating limestone is a thermal decomposition reaction. Two new substance are made in this reaction Calcium carbonate  Calcium oxide + Carbon dioxide CaCO 3  CaO + CO 2 CaCO 3  CaO + CO 2 Next page

15. Making concrete Main menu Back to C2b cementclay A lot of limestone is made into cement. Limestone and clay are heated together. Concrete cement, sand, gravel and water Concrete is a useful construction material. It is made from cement, sand, gravel and water. reinforced Concrete is not very strong unless it is reinforced. steel rods Putting steel rods in concrete reinforces it. stronger cracking This makes the beams stronger and prevents its from cracking. Next page

16. Problems with rocks Main menu Back to C2b quarryenvironmental Obtaining rocks from a quarry can cause environmental problems valuable land space They take up valuable land space landscapes They destroy landscapes environment Destroy the environment of plants and animals dustnoise Increase dust and noise levels Next page

17. Click here to take you to a quiz on “Construction Materials” Main menu Back to C2b Next page

18. Structure of the Earth Plate tectonics Evidence for plate tectonics Subduction Volcanoes Main menu Download podcast here Next page

19. Structure of the Earth Main menu Back to C2c solid rock Crust is solid rock molten rock Mantle is molten rock liquid iron and nickel Outer core is liquid iron and nickel. It is very dense. solid iron and nickel Inner core is solid iron and nickel. It is very dense. Next page

20. Plate tectonics Main menu Back to C2c lithosphere tectonic plates The crust and the upper mantle is called the lithosphere. The lithosphere is made up of large sections called tectonic plates. floatfew cm These plates float on top of the mantle. They move a few cm each year. convection currents The liquid in the mantle can move because of convection currents and carry the plates with it. Next page

21. Evidence for plate tectonics Main menu Back to C2c fit together Africa and South America look like they fit together suggesting they were once joined. Fossilsrocks Fossils and rocks have been found on both continents. Earthquakesvolcanoes Earthquakes and volcanoes occur where plates meet. Next page

22. Subduction Main menu Back to C2c oceaniccontinental underneath When an oceanic plate and a continental plate collide, the oceanic plate is forced underneath the continental plate. melts The oceanic plate melts in the magma. subduction This is called subduction. fold mountains The continental plate forms fold mountains. Next page

23. Volcanoes Main menu Back to C2c Volcanoes Volcanoes are formed where there are weaknesses in the Earth’s crust. Molten rock can make its way to the surface. Geologists Geologists study volcanoes. fertile crops People choose to live near volcanoes because the land is fertile and lots of crops can be grown. There are two types of volcanic rock Extrusive igneous Extrusive igneous rocks form outside the Earth and have small crystals Intrusive igneous large crystals Intrusive igneous rocks form in side the Earth’s crust and have large crystals Next page

24. Click here to take you to a quiz on “Does the Earth move?” Main menu Back to C2c Next page

25. Extracting copper Purifying copper Alloys Smart alloys Main menu Download podcast here Next page

26. Main menu Extracting Copper Back to C2d wirespipes Copper is a useful metal used in wires and pipes displacement Copper is extracted from its ore using displacement with carbon. reactive This is because carbon is more reactive than carbon Copper oxide + Carbon  Copper + Carbon dioxide 2 CuO + C  2 Cu + CO 2 2 CuO + C  2 Cu + CO 2 Next page

27. Main menu Purifying copper Back to C2d electrolysis99.9% Copper can be purified using electrolysis. It must be 99.9% pure to be used in wires. electrodes electrolyte Rods called electrodes are placed in an electrolyte (copper sulphate) cathode Copper metal forms on the cathode Cu 2+ + 2e -  Cu anode Copper from the anode becomes ions in solution Cu – 2e -  Cu 2+ Next page

28. Main menuAlloys Back to C2d alloymetal An alloy is a mixture of elements where at least one is a metal. useful Metals are more useful as alloys. Alloy Main Metal Use AmalgamMercuryTooth fillings BrassCopper & Zinc Hinges, screws, instruments BronzeCopper & TinStatues SolderTin & LeadJoining metals, circuits SteelIronCar bodies, ships Next page

29. Main menu Smart Alloys Back to C2d shape memory alloys Smart alloys are also known as shape memory alloys. original shape hot waterelectric current Shape memory alloys can return to their original shape when put in hot water or an electric current is passed through it. Uses of shape memory alloys are:  originally for military uses  medical uses  spectacle frames Next page

30. Back to C2d Main menu Click here to take you to a quiz on “Metals and Alloys?” Next page

31. Corrosion of iron Corrosion of aluminium Properties of iron and aluminium Car bodies Main menu Download podcast here Next page

32. Corrosion of Iron Main menu Back to C2e rusts Iron is the only metal that rusts. oxygenwater salt wateracid rain Iron needs oxygen and water to rust. Rusting is speeded up by salt water or acid rain. Iron + Oxygen + Water  Hydrated Iron Oxide Next page

33. Corrosion of Aluminium Main menu Back to C2e not corrode Aluminium does not corrode even in damp conditions. layer aluminium oxide This is because it forms a layer of aluminium oxide. This prevents the surface from corroding. Next page

34. Properties of Iron and Aluminium Main menu Back to C2e PropertyIronAluminium DensityDenser than steelLees dense than iron MagnetismMagneticNot magnetic CorrosionRusts easilyDoes not corrode easily MalleabilityMalleable ConductivityGood conductor Next page

35. Car Bodies Main menu Back to C2e car bodies harderstronger Steel is used to make car bodies. It is harder and stronger than iron. It is also less likely to corrode than iron. expensive Stainless steel was used to make a car body. It is more expensive than steel but did not rust. Aluminium can be used instead of steel. lighter better fuel economy Aluminium cars are lighter and give better fuel economy. An aluminium frame also corrodes less, more However, repair costs are approximately 25% more than steel. Next page

36. Click here to take you to a quiz on “Cars for Scrap?” Main menu Back to C2e Next page

37. Composition of air Evolution of the atmosphere Air pollutants Controlling air pollution Main menu Download podcast here Next page

38. Composition of Air Main menu Back to C2f Air is a mixture of gases. nitrogen It is:- 78% nitrogen oxygen 21% oxygen other gases 1% other gases carbondioxide, water vapour and argon The other gases include carbon dioxide, water vapour and argon. Next page

39. Evolution of the Atmosphere Main menu Back to C2f constant The atmosphere has remained constant for millions of years. volcanic carbon dioxide, water vapour, methane and ammonia Atmosphere formed from volcanic eruptions was made of carbon dioxide, water vapour, methane and ammonia. cooled oceans Water vapour cooled and formed oceans. Plants carbon dioxide into oxygen Plants form and convert carbon dioxide into oxygen Next page

40. Air Pollutants Main menu Back to C2f Pollutant How is it formed? Problem Carbon monoxide Formed from incomplete combustion in car engines Is a poison and prevents oxygen transport around body Nitrogen oxides In car engines from the reaction of nitrogen with oxygen Creates smog, acid rain and breathing problems Sulphur dioxide Combustion of fossil fuels containing sulphur e.g. coal Acid rain Next page

41. Controlling Air Pollution Main menu Back to C2f balancechanged The balance between carbon dioxide and oxygen can be changed by humans energy  Increasing energy use means more carbon dioxide  Population  Population increase means more carbon dioxide  Deforestation  Deforestation means more carbon dioxide Catalytic converters carbon monoxidenitrogen oxides carbon dioxidenitrogen Catalytic converters can be fitted to car exhaust systems to change poisonous carbon monoxide and nitrogen oxides into carbon dioxide and nitrogen. Next page

42. Click here to take you to a quiz on “Clean Air?” Main menu Back to C2f Next page

43. What are rates? Measuring rates Rates and graphs Temperature and rates Concentration and rates Main menu Download podcast here Next page

44. What are Rates? Main menu Back to C2g differentrate of reaction Chemical reactions are different. The rate of reaction is the time it takes for a reaction to complete. Next page

45. Measuring Rates Main menu Back to C2g measure how long product to form reactant to be used up We can measure the rate of reaction by timing how long it takes for a product to form (e.g. a gas) or a reactant to be used up (e.g. a solid) Next page

46. Rates and Graphs Main menu Back to C2g steeply stopped The graph starts steeply. This is when the reaction is fastest. When the line is flat, the reaction has stopped. steepest linequickest We can compare two reactions. The one with the steepest line is the quickest reaction. initial rate volume of gas(cm 3 ) We can calculate initial rate of reaction by working out the gradient = volume of gas(cm 3 ) time(s) time(s) Next page

47. Temperature and Rates Main menu Back to C2g collide Particles of reactants must collide for a reaction to occur. increasedfaster more energy As the temperature is increased the particles move faster because they have more energy. more often energy This means the particles collide more often and with enough energy. More collisions mean a faster reaction. Next page

48. Concentration and Rates Main menu Back to C2g increasedmore particles As the concentration is increased there are more particles in a given volume. closer The particles are closer together more collisions There will be more collisions and the reaction will be faster. Next page

49. Main menu Back to C2g Click here to take you to a quiz on “Faster or Slower 1?” Next page

50. Surface area and rates Catalysts and rates Main menu Download podcast here Next page

51. Main menu Back to C2h Surface Area and Rates solid reactantsmaller pieces If we break up a solid reactant into smaller pieces, we increase the surface area. more frequently Because more surface area is exposed, the particles collide more frequently. More collisions mean a faster reaction. Next page

52. Main menu Back to C2h Catalysts and Rates speed up Catalysts are chemicals which speed up a chemical reaction. not used up happen faster They are not used up during a reaction and do not change how much product is made, they just make it happen faster. specific Catalyst are specific – each catalyst only works for certain reactions Next page

53. Main menu Back to C2h Click here to take you to a quiz on “Faster or Slower 2?” Next page