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C2 Contents

C2 Contents

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C2 Contents

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  1. How to Operate This PowerPoint Select slideshow and click on “From Beginning”. Click once and this box will disappear, then choose the section you wish to look at and click on next to it. C2 Contents The Structure of the Earth Construction Materials Metals and Alloys Making Cars Making Ammonia Acids and Bases Fertilisers and Crop Yield The Chemistry of Sodium Chloride

  2. C2: Chemical Resources The Structure Of The Earth Learning Objectives All: To be able to describe the three layers of the Earth Most: To be able to explain the role of tectonic plates Some: To be able to predict the effects of cooling on crystal size Starter: Write down three things you know about the structure of the Earth

  3. Inside the Earth 1. 2. 4. 3.

  4. The Core • The radius of the Earths core is just over half the radius of the Earth • The core contains two layers • The inner core is mostly solid nickel and iron • The outer core is liquid nickel and iron

  5. The Mantle • This is the layer between the crust and core • The mantle has a variable temperature and consistency • The mantle has the properties of a solid but moves slowly • This motion is caused by energy being transferred via convection currents

  6. The Lithosphere • This is the outermost layer of the Earth – it contains the oceanic and continental plates (the crust) and the very top part of the mantle • The tectonic plates are less dense than the mantle and float on top of it • The oceanic plates are between 3 and 5 miles thick • The continental plates can be up to 70 miles thick under mountains • As the crust is too thick to drill through scientists study seismic waves (either from earthquakes or man-made explosions)

  7. Continental Drift • Over thousands of years the plates drift thousands of kilometres – this is continental drift • This is the accepted theory explaining the Earths surface – it has been tested and discussed by many scientists • Tectonic plates move very slowly (approx 2.5cm/yr) • Their movement causes volcanoes and earthquakes

  8. Plate Tectonics • It can also cause partial re-melting • The oceanic plates are less dense than the continental ones • When the oceanic and continental plates collide the less dense, cooler oceanic plates sink and are pulled down under the continental ones • This is called subduction

  9. Alfred Wegener • Alfred Wegener came up with the idea of plate tectonics and continental drift in 1914 • He suggested that mountains were formed when the edges of plates collide, crumple and fold • It took 50 years for the theory to be accepted because it was difficult to work out how the continents could move • Until the spreading of the seafloor was discovered in the 1960’s there was not enough evidence to support the theory fully

  10. lava layers of igneous rock main vent side vent ash cloud magma

  11. Making Rock • Volcanic activity is one of the ways rocks are formed • Cooling magma creates igneous rocks • The size of the crystals in igneous rocks depends on how long it took to cool • Slow cooling leads to large crystals (e.g. gabbro), fast cooling gives small crystals (e.g. basalt)

  12. Rock Creation • Lava (outside the Earth) can be runny or thick (from violent explosions) • Runny magma (inside the Earth) has a different composition to thick magma and this dictates what type of eruption occurs and the type of rock that is formed • Basalt is rich in iron and comes from the runny lava of a “safe” eruption • Rhyolite is rich in silica and comes from the thick lava of an “explosive” eruption

  13. Vulcanology • This is the study of volcanoes • Geologists that study volcanoes are call vulcanologists • They try to use the knowledge to predict future eruptions and to study the structure of the Earth • They are NOT 100% accurate • Some people live near volcanoes voluntarily because the soil is very fertile

  14. C2: Chemical Resources Construction Materials Learning Objectives All: To be able to recall the names and uses of some construction materials Most: To be able to explain the different properties of rocks Some: To be able to predict environmental impact of mines and quarries Starter: Name as many building materials as you can

  15. Building Materials • Where do these materials come from? • Bricks – made from clay • Glass – from sand • Cement – from limestone • Concrete – from limestone • Aluminium – from ore • Iron – from ore • Granite – mine/quarry • Marble – mine/quarry • Limestone – mine/quarry

  16. Rock Types Hardness Granite • Hardest • Igneous Limestone • Softest • Sedimentary Marble • Metamorphic • Formed from limestone under heat and high pressure

  17. Uses of Limestone • Limestone mixed with clay and heated makes cement • If you mix cement with sand and water and leave to set you get mortar • If you mix cement with gravel and water and leave to set you get concrete

  18. Reinforced Concrete • The steel support is placed into a mould and the concrete poured in around it • Reinforced concrete is a composite material • Concrete is very good when squashed but is weak when stretched • Steel is flexible and strong when stretched • By combining the two you get reinforced concrete

  19. Thermal Decomposition • Both limestone and marble are mostly made of calcium carbonate • Calcium carbonate shows thermal decomposition • When it is heated the one substance breaks down into two new substances • Limestone does this but so do other metal carbonates • Copper (II) carbonate breaks down into copper (II) oxide and carbon dioxide, changing from green to black as it does so

  20. Calcium Carbonate • When calcium carbonate decomposes this is what happens Calcium Carbonate Calcium oxide + Carbon Dioxide CaCO3CaO + CO2 • The calcium oxide is then used to make the lime for cement to make concrete

  21. Getting Rocks • Marble, granite and limestone are all rocks used in construction • Iron and aluminium are extracted from ores • How do we get these rocks? • Mining and quarrying

  22. Limestone Quarrying Benefits Drawbacks • Limestone is used to make concrete and glass • Limestone quarries provide employment and support local economies • Destroy the landscape and are visible from long distances • Quarrying is a heavy industry that creates dust, noise and heavy traffic

  23. C2: Chemical Resources Metals and Alloys Learning Objectives All: To be able to recall what an alloy is Most: To be able to describe the extraction of copper Some: To be able to explain how electrolysis is used to purify copper Starter: Make a list of what copper is used for

  24. Extracting Metals • Most metals are found in ores and need to be extracted • Carbon is more reactive than copper • If a copper ore is heated with carbon (e.g. charcoal) the carbon will react with the ore and leave copper • The loss of oxygen is called reduction – the copper (II) oxide has been reduced Copper (II) oxide + carbon copper + carbon dioxide 2CuO + C 2Cu + CO2

  25. Recycling • The world is running out of copper-rich ores • Recycling copper is cheaper and uses less energy than extracting copper • Extracted copper and recycled copper can both be impure • Copper is purified by electrolysis

  26. Electrolysis • Electrolysis uses electricity to separate substances • Some pure copper is attached to a negative electrode – the cathode • The impure copper is attached to the positive electrode – the anode • The electrodes are placed in a solution that contains copper compounds e.g. copper (II) sulphate – the electrolyte

  27. Electrolysis • The electricity flows, passing electrons around the circuit • The anode looses mass as the copper dissolves, leaving behind the impurities as sludge • The cathode gains mass as the pure copper is deposited on it • At the anode the copper looses electrons – it is oxidised • At the cathode the copper gains electrons – it is reduced • Remember: OIL RIG(Oxidation Is Loss, Reduction Is Gain)

  28. Electrolysis + - e- Cu2+ Cu Anode – impure copper Cu – 2e-→ Cu2+ Cathode – pure copper Cu2+ + 2e-→ Cu Sludge

  29. Alloys • What is an alloy? • An alloy is a mixture of 2 elements, one of which is a metal • How many alloys can you name? Do you know what they are made of? • Brass – copper and zinc • Solder – lead and tin • Amalgam – mercury • Steel – iron and carbon

  30. Importance of Alloys • The properties of alloys are usually different to the properties of the metal they contain • The atoms of the different substances are different sizes which stops the atoms forming a regular arrangement • This means that they tend to be harder than the pure metal because the atoms cannot slide over each other as easily

  31. Alloy Properties • The properties of the alloy make them suitable for specific jobs • Solder has a low melting point and conducts electricity well • Nitinol is a “smart alloy” made of nickel and titanium • If it is bent out of shape it returns to its original shape when it is heated or has an electrical current pass through it • It is called a memory shape alloy

  32. C2: Chemical Resources Making Cars Learning Objectives All: To be able to describe the conditions needed for rusting to occur Most: To be able to explain the pros and cons of making cars from recycled material Some: To be able to compare different metals and alloys as materials for making cars Starter: How many things can you name that are made of iron/steel

  33. Rusting • When a metal reacts with the air, water or surroundings it is said to be corroded • When iron or steel corrodes it is called rusting • What does iron need to rust? • Water and oxygen • Iron + oxygen + water hydrated iron (III) oxide • This is a type of oxidation • What could speed it up? • Salt water • Acid rain

  34. Corroding Aluminium • Water and oxygen makes iron rust – what affect does it have on aluminium? • Aluminium does not corrode in these conditions • The aluminium reacts with the oxygen to form a clear layer of aluminium oxide which prevents the oxygen and water from reaching the metal below • This aluminium oxide does not flake off like rust can

  35. Iron v Aluminium • More dense • Magnetic • Easily corrodes • Malleable • Conducts electricity well • Less dense • Non-magnetic • Doesn’t corrode easily • Malleable • Conducts electricity well

  36. Iron and Steel • Steel is an alloy of iron and carbon • It is stronger and harder than iron • It does not corrode as easily as iron

  37. Building Cars • Aluminium is less dense than steel or iron – this means that an aluminium car will be lighter and use less fuel • Aluminium does not corrode easily like steel and iron – an aluminium car should last longer • Aluminium is more expensive than steel or iron – an aluminium car will cost more to buy

  38. Making Cars • What materials are used to make cars? • Steel, copper, aluminium, glass, plastic, fabric, rubber • Which material is used for which job depends on the properties of that material e.g. you would not make tyres from glass or windows from rubber

  39. Car Materials

  40. Recycling • EU law now requires that 85% of a cars materials can be recycled • This is to rise to 95% by 2015 • Recycling reduces the amount of waste and slows down the use of natural resources

  41. C2: Chemical Resources Making Ammonia Learning Objectives All: To be able to describe the Haber Process Most: To be able to explain conditions needed for the Haber Process to occur Some: To be able to predict how different factors will affect the cost of the Haber Process Starter: What is meant by the term reversible reaction?

  42. Ammonia • Its chemical formula is NH3 • Some ammonia is used in fertilisers, explosives and cleaning fluids • Some ammonia is turned into nitric acid which is also used in fertilisers and explosives

  43. Plants and Ammonia • For plants to grow they need protein and to make protein they need nitrogen • Plants cannot get the nitrogen from the air – they need to absorb a solution of water and nitrogen compounds • Ammonia based fertilisers provide this

  44. Making Ammonia • Ammonia is made by combining nitrogen and hydrogen in the Haber process • It is a reversible reaction • Nitrogen + Hydrogen Ammonia • The nitrogen comes from the air – approx 78% of air is nitrogen, when hydrogen is burned in air it combines with the oxygen and leaves the nitrogen behind • The hydrogen comes from cracking hydrocarbons or by reacting gas with steam • Any unreacted hydrogen and nitrogen is recycled back into the process

  45. Haber Process Carbon Monoxide Methane Steam Hydrogen Air Water Nitrogen Ammonia N2 + 3H2→ 2NH3 450C, 200atm, iron catalyst

  46. Conditions • The Haber process uses a high temperature, high pressure and a an iron catalyst • Like all industrial processes the conditions are chosen to give the highest percentage yield for the cheapest price • The percentage yield is the amount of product made compared to the amount of reactant put in e.g. if half the nitrogen and hydrogen becomes ammonia then the yield is 50%

  47. Conditions • The higher the pressure the higher the percentage yield of ammonia but high pressures are expensive • High temperatures give a fast reaction but a low percentage yield • The catalyst speeds up the reaction but does not alter the amount of ammonia made

  48. Making Chemicals • When industry makes chemicals they try to produce as much as they can for as little money as possible – this increases the profit • They call these conditions the optimum conditions – they may not give the fastest reaction or highest yield • The rate of reaction and percentage yield must be high enough to produce enough product each day – if unreacted products can be recycled then a lower percentage yield will be acceptable

  49. Making Chemicals • When industry makes chemicals they try to produce as much as they can for as little money as possible – this increases the profit

  50. C2: Chemical Resources Acids and Bases Learning Objectives All: To be able to describe a neutralisation experiment Most: To be able to explain the difference between an alkali and a base Some: To be able to predict the salt made by a reaction Starter: what is a) an acid? b) a alkali? c) pH? d) universal indicator? e) neutralisation?