Earth’s structure

1. C2

2. Tectonic plates = move 2.5cm per year. = millions of years to form continents. Plate tectonics Theory Convection currents in the mantle = plates move. Oceanic crust less dense than continental crust. Collision between oceanic and continental plates = subduction and melting Plates cooler at ocean margins so sink Thin, rocky crust Iron core Mantle Just below crust = cold, rigid Deeper down = hot, can move Lithosphere Crust + upper mantle Made of tectonic plates Tectonic plates = less dense than mantle  float The development of the Plate Tectonics theory Wegner came up with continental drift in 1914. Not accepted by scientists – Wegner wasn’t a geologist, it went against their ideas. 1960s – sea floor spreading discovered – supported theory. More research supports it. Theory accepted. Plate tectonics is widely accepted It explains lots of evidence Discussed and tested by lots of scientists. Volcanoes – studied to predict eruptions - to find out the Earth’s structure Better predictions now – better measurement techniques and theories – still not 100% People live there – fertile soil Lava Slow cooling = big crystals Thicker lava = more dangerous eruption Problems with studying the Earth’s structure Crust is too thick to drill through. Have to use S and P waves from man-made explosions Earth’s structure

3. Rocks used in construction Limestone = soft - sedimentary rock - layers Marble = hard- metamorphic rock - -made by high temperature and pressure Granite = really hard – igneous rock Construction Materials Limestone Quarrying destroys the landscape, causes noise, traffic and dust. Thermal decomposition A reaction where heat is used to breakdown one substance into at least two new substances. calcium carbonate  calcium oxide + carbon dioxide CaCO3  CaO + CO2 Concrete Cement + sand + gravel + water then let it set. Reinforced Concrete Concrete + steel Composite material (mixture of two materials = mixture of their properties.) Reinforced concrete is better than normal concrete. It is as hard as normal concrete Steel makes it more flexible and stronger in tension (when you stretch it). Cement = limestone and clay heated together.

4. Alloys Mixtures containing one or more metals elements. • Extraction of Copper • Extracted from its ore using carbon. • Reduction reaction – because oxygen is removed from the copper • Then purified by electrolysis Smart Alloys Shape memory – can bend, warm up and then it returns to shape. Nitinol – bendy glasses frames – returns to original shape after bending Metals and Alloys Purification of Copper details Impure copper as anode. Pure copper as cathode Copper sulfate solution as electrolyte Cathode gains mass as copper is deposited. Cu2++ 2e- Cu – reduction (RIG) Anode loses mass as copper dissolves. Cu – 2e- Cu2+ - oxidation (OIL)

5. Rusting • Is an oxidation reaction because oxygen is added to the iron. • Iron + oxygen + water  hydrated iron (III) oxide • Rusting happens faster when the water is salty or acidic • Aluminium does not corrode because • A layer of aluminium oxide forms on the surface • Aluminium oxide is strong Recycling and Cars EU law says 85% of a car should be recyclable. Advantages of recycling car parts Saves metal resources because less has to be mined. Saves money and energy Less crude oil is used to make plastic parts Glass has been recycled for a long time so is easy to do. Batteries contain toxic material so it is better that this is not dumped. Disadvantage All the different materials need to be separated first. Making Cars Alloys Have properties that are different to the metals they are made from which can make them more useful Steel is harder and stronger than iron Steel is less likely to corrode than iron.

6. Making Ammonia • Ammonia is made in the Haber process • nitrogen + hydrogen ammonia • N2 + H2 NH3 • Needs: • Nitrogen – from the air • Hydrogen – from natural gas or crude oil • Iron catalyst –increases the rate and does not affect the % yield • High pressure – higher pressure increases the % yield of ammonia • Temperature of about 450oC – high temperature decreases the % yield of ammonia but gives a faster reaction – we choose a compromise temperature for a high rate and quite high yield. • Unreacted nitrogen and hydrogen are recycled. Costs and Industry High pressure – high cost of equipment High temperature – high energy cost Catalyst – reduces cost by increasing rate Recycling the unreacted nitrogen and hydrogen reduces costs Automation – reduces the wages bill Rate and % yield = high enough for sufficient daily rate. Low % yield sometimes ok if the starting materials are recycled many times. Optimum conditions = lowest cost (not fastest reaction or highest yield) Ammonia Uses Ammonia is used to make fertilisers and nitric acid.

7. This powerpoint is not quite finished. Email Mrs McDermott now to get the rest of the slides. m.mcdermott@marriotts.herts.sch.uk