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Structure of the Earth

Outer layer of Earth is called the lithosphere (relatively cold and rigid and comprises (made up of) the crust and top part of the mantle

Litosphere is made up of tectonic plates which are less dense than the mantle below

Crust is too thick to drill through so most information about Earth is collected from seismic waves produced by earthquakes and man-made explosion

Most scientists accept theory of plate tectonics- it suggests Africa and S America could have once been one land mass as it explains a wide range of evidence and has been discussed by many scientists

In 1960s sea floor spreading evidence was found which led to Wegeners theory about continental drift theory slowly becoming accepted.

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Tectonic plates and Subduction

Mantle is the zone between the core and the crust. -cold and rigid below the crust but hot and non-rigid and able to move more towards the core

Earths core transfers energy so temp of the mantle increases with depth-Convection currents slowly move plates                                                                                                                           Oceanic crust denser continental crust so when they collide at a destructive margin, oceanic plate sinks pulling more of the plate down and partly melting as it reaches hotter part of the mantle- this is called subduction and collisons create mountains                                                      Crust is weakned so magma can escape through tiny cracks in the crust and volcanoes are formed

Magma can have different types of composition wich causes different types of eruptions so geologists study volcanoes to try to forecast future eruptions (cant be 100% certainty)  and reveal more about the structure of the earth

Iron-rich basalt rock comes from runny lava in slower volcanic eruptions 

Silica-rich rhyolite rock comes from thick lava is explosive eruptions

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Construction materials

-some raw materials used to make construction materials can be found in the earths crust

-hardness of rocks can be compared by rubbing two materials together                

Granite is harder than marble and marble is harder than limestone                                                 -Many buildings look like they're made fromone material but infact they are made with two and only lines with and expensive material

Limestone- sedimentary rock made from soft sediments compressed and cemented together so this makes likestone quite soft

Marble- metamorphic rock formed when limestones is changed by heat and pressure and typically composed of an interlocking mosaic of carbonate crystals (marble is harder than limestones as it has been baked)

Granite- formes when magma cools and solidifies so it's an igneous rock with interlocking crystals so this makes it very hard

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Reinforced concrete & building materials

Concrete=strong under compression(squashing force) but weak under tension (pulling force)

Heavy loads applied to beam=concrete will bend which creates tension (cracks) and compression

Reinforced concrete (harder & more flexible than concrete) =has steel rods/meshes running through it to stop it from stretching and cracking so its a better constuction material

Reinforced concrete (composite material=contain at least two materials that can still be distinguished)

Raw material=building material

clay=brick   limetone&clay=cement    sand=glass    iron ore=iron   aluminium ore=aluminium

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Thermal decomposition=reaction when one substance breaks down on heating to give at least two new substances

limestone=calcium carbonate thermally decomposes when heated

when limestone is heated with clay=cement is made

Calcium carbonate-> calcium oxide+ cardon dioxide

CaCO3-> CaO + CO2

concrete is made when mixing cement+sand+small stones+water

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alloys=mixtures containing at least one metal

alloys have different properties & we match the alloy to the job we use it for

Amalgam- contains mercury (fillings)

Brass- contains copper and zinc (instruments and ornaments)

Solder- contains lead and tin (heated up and used to joing metals) (circuits)

Smart alloys return to their original shape after being heated to a certain temperature

Nitinol (nickel-titanium) is a smart alloy which is used to make spectacle frames as it returns to its original shape after being bent if it is put in hot water

Smart alloys are becoming more popular as new ways to use them are being found

steel is harder and stronger than iron and less likely to corrode than iron

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Making cars

-iron and steel rust, other metals corrode          -acid rain and salt water accelerate rusting    -Rusting is an oxidation reaction because iron reacts with oxygen forming an oxide               Equation for rusting=  iron+oxygen+water -> hydrated iron(III) oxide                             -Aluminium doesnt corrode in moist air as it has a protective layer of aluminium oxide which unlike rust doesnt flake off the surface          -(different metals corrode at different rates)

Recycling: materials from old cars

+less mining saves finate resources needed to make metals                                                                  +less crude oil needed to make plastics       +less waste means less landfill                                                                         +fewer toxic materials such as lead from bateries are dumped

-fewer mines are build=fewer mining jobs created                                                                                -difficult to separate different materials                                                                                                 -some recycling processes are very expensive                                                                                    -some separating techniques product pollution

laws which specify that a minimum % of all materials used to manufacture cars must be recyclable to help protect the environment

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Materials used in cars

Different materials are used in cars as  they have different properties                                             Car bodies made from steel/aluminium have +&- as aluminium is lighter and more resistant to corrosion but steel costs less and is stronger. lighter aluminium body means that fuel economy is improved because aluminium corrodes slowly the car body will also last longer

aluminium is used in car bodies and wheel hubs  doesn’t corrode,low density,malleable,quite strong

iron/steel in car bodies        malleable and strong

copper in electrical wires        ductile and good electrical conductor

lead in lead-acid batteries      chemical rection with lead oxide produces electricity

plastic in dashboards,bumpers,dials        rigid,doesn’t corrode and is cheap

glass/plastic composite in windscreens       transparent and shatterproof (may crack though)

pvc in metal wire coverings     flexible, doesn't react with water and electrical insulator


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Copper electrolysis

Electrolysis is purifying impure copper                                                                                                 -electrode of copper(II) sulfate solution is used                                                                                   -impure copper is the anode(+) and sheet of pure copper is the cathode(-)                                           -Positive anode loses mass as the copper dissolves and negative cathode gains mass as pure copper is plated onto it                                                                                                                         -Concentration of the copper(II) sulphate electrolyte stays the same because as the impure copper anode dissolves the pure copper is plated onto the cathode at the same rate               anode: Cu – 2e¯ → Cu²+ (oxidation)                                    (OIL RIG)                                                                     cathode: Cu²+ + 2e¯ → Cu (reduction)

Recycling copper;     +fairly low melting point so energy cost to melt is low                                                      +reduces need for mining saving reserves and the environmental problems caused by mining     +keeps the cost of copper down                                                                                                               -small ammounts used in electrical equipment are difficult to separate                                           -less copper is mined=less jobs        -actual separating process may produce pollution                      -a lot of copper is thrown away as it's difficult to persuade people to recycle it                                                   -valuable pure copper scrap cant be mixed with less pure scrap such as solder

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Haber Process

world food production depend on nitrogen fertilisers(made from ammonia)                                                                 word equation for harber process-     nitrogen+hydrogen<->ammonia (N2+3H2<->2NH3)     Optimum conditions for the Harber process are;                                                                                                        -catalyst made of iron increases reaction rate (rate of successful collisions)                                   -high pressure(200 atmospheres) increaes the percentage yield of ammonia                                 -temperature of 450C(low for industrial process) increases the reaction rate and a very high temperature breaks down ammonia reducing % yield=although not a very high yield the rate is fairly quick and the best comprommise                                                                                                        -recycle any unreacted nitrogen and hydrogen

Cost of chemical manufacture;                                                                                                                            -costs increase when pressure raised and temperature is raised                                                                    -costs decrease when catalysts are used, unreacted starting materials are recycled and automation is used                                                                                                                                -economic considerations determine conditions used to manufacture a chemical                         -reaction rate and percentage yield must be high enough to give sufficient daily yield of product and a low percentage yield can be accepted if the reaction can be repeated many times with recycled starting materials                                                                                                        (optimum conditions give lowest cost rather than fastest rate or highest yield)

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Acids and bases

-metal oxides/hydroxides are bases and a few bases are soluble in water (alkalis)                         -neutralisation takes place when an acid and a base react to mkae salt and water                              -word equation for neutralisation=       acid+base->salt+water             

-some indicators show sudden change of colour at one pH value and a univeral indicator shows a gradual range of colour changes as it contains mixture of different indicators

-In solution acids contain H+ ions and the pH of an acid is determined by the concentration of H+ ions=higher the concentration the lower the pH

Alkalis contain OH- (hydroxide) ions           neutralisation-    H+ + OH- <-> H2O

common salt            second part of the salt name

sulphuric                    sulfate

nitric                            nitrate

hydrochloric                 chloride

phosphoric                phosphate

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-acids react with bases and metal carbonates to form salts

- acid + metal carbonate-> salt+water+carbon dioxide

hydrochloric acid+copper carbonate->copper chloride+water+carbon dioxide

2HCL + CuCO3 ->  CuCL2  +  H2O   +   CO2

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Growing crops

-farmers use fertilisers to increase crop yield

-fertilisers must be dissolved in water before they can be absorbed by plant roots as only dissolved substnces are small enough to be absorbed

-some fertilisers dissolve easily but others are slow release giving crops a small ammount over a long period of time

-fertilisers are needed as world population is rising=greater demand for food production from the land available

-fertilisers increase crop yield by replacing essential elemts used by previous crops or providing extra essential elements 

-also fertilisers provide nitrogen that is incorporated into plant protein resulting in increased growth

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if fertilisers get into water they encourage algae growth leading to eutrophication;

Eutrophication happens when;

-fertilliers washed off fields and fertilisers in water increase nitrate and phosphate levels

-algae grow quickly on the surface in the presence of these chemicals (algae bloom)

-algae block off sunlight to other oxygen-producing plants which die

-aerobic bacteria use up the oxygen in the water and feed on the decaying plants

-most living organisms die in the water

-excessve use of fertilisers can also pollute water supplies

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Preparing fertilisers

-most fertilisers are salt so they can be made by reacting and acid and alkali to make salt and water (react nictric acid and ammonia solution to make ammonium nitrate)

-Process of producing a fertiliser from reaction of and acid and alkali follows;

1.alkali titrated with acid using an indicator to find out the quantities needed before the main batch is made (repeated until results are consistant)

2.acid and alkali have now reacted compleatly to produce a neutral solution of ammonium sulfate fertiliser however this is contaminated with indicator solution

3.titrated results are used to repeat experiment using correct quantities

4.dissolved fertiliser is heated to evaporate most of the water off then left for the remaining solution to crystalise

5.crystals are then filtered off

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Mining and subsidence

Salt is mined in Chesire in 2 different ways;

-mining it from the ground as rock salt

-solution mining by pumping in water and extracting saturated salt solution

mining salt can lead to subsidence-> the ground above a mine can sink causing landslips and destroying homes

salt at the surface especially brine solution can escape and affect habitats

Chlor-alkali industry

Sodium hydroxide and chlorine are used to make household bleach

Chlorine and sodium hydroxide are important raw materials as they are involved in making about half the chemicals we use on a daily basis including solvents, plastics, soaps and medicines.

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Electrolysis of sodium chloride solution

-concentrated sodium chloride solution (brine) can be separated by electrolysis

-hydrogen is made at the negative cathode

-chlorine is made at the positive anode

-sodium hydroxide forms in solution

-hydrogen and chlorine are reactive so its important to use inert electrodes so the products dont react before they are collected and the electrodes dont dissolve

-during electrolysis of NaCl solution  Na+ and H+ ions migrate to negative cathode

-Cl- and OH- ions migrate to positive cathode

-at the cathode hydrogen is made -electrons are gained so this is reduction 

-at the anode chlorine is made -electrons are lost so this is oxidation

-ions not discharged make sodium hydroxide solution

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