C2

1. crust - relatively thin and rocky
2. mantle - has the properties of a solid, but can flow very slowly
3. outer core - made from liquid nickel and iron
4. inner core - made from solid nickel and iron
5. The lithosphere consists of the crust and outer part of the mantle.

• It is difficult to study the structure of the Earth because:
  • the crust is too thick to drill all the way through
  • scientists need to study seismic waves made by earthquakes or man-made explosions.
• core is just over half the earths radius
• radioactive decay creates a lot of the heat inside the earth. this heat creates convection currents in the mantle, which causes the plates of the lithosphere to move

• lithosphere is cool outer part of structure. broken into large pieces called tectonic plates - less dense than the mantle underneath
  • as they move, the continents move speed of 2.5cm per year
  • volcanoes and earthquakes occurs where plates meet - movement against each other cause

Seismic Waves tell us whats below the crust

• difficult to study inner structure - use seismic waves (produced by earthquakes/explosions) to study
• by measuring time it takes to travel through earth and where detected we can draw conclusions about structure of earth
  • 2 types of seismic waves - P-waves and S-waves
    • p-waves travel through solids and liquids - travel faster through middle of core so inner core is solid
    • s-waves travel through solids - travel through mantle shows solid but not detected in cores shadow so outer core is liquid

• The theory of plate tectonics and continental drift was proposed at the beginning of the last century by Alfred Wegener
  • over millions of years ago there had just been one "supercontinent" (pangaea). over time it broke apart and slowly drift apart. This process is called continental drift.
  • suggested that mountains were formed when the edge of a drifting continent collided with another, causing it to crumple and fold.
  • suggested africa and south america were wonce one continent which had been split
    • evidence - matching layers in rocks on different sides of continent; similar earthworms in south america and south africa

It took more than 50 years for Wegener’s theory to be accepted, beacuse:

• it was difficult to work out how whole continents could move
• it was not until the 1960s that enough evidence was discovered to support the theory fully

• magma rises up through crust and 'boils over' - sometimes violently if pressure is released suddenly.
  • molten rock below crust is magma, above crust is lava
• subduction - crust at ocean floor is denser then crust below continents so when they collide denser plate forced underneath less dense plate
  • oceanic crust cooler at edges so edges sink easily pulling plate down
  • as its forced down it melts and rises. if this molten rock surfaces, volcanoes form
• igneous rocks - molten rock cools and solidifies
  • iron-rich basalt magma - lava is runny, fairly safe eruption
  • silica-rich rhyolite magma - lava is thick, eruption is explosice
• Geologists predict volcanic eruptions by studying magma movement below ground near volcano
  • HOWEVER volcanoes are unpredictable so nothing is certain, but even knowing a little can save lives

• Sedimentary
  • layers of sediment lay in lakes/seas; over millions of years layers get buried under more layers and weight squeezes out water; fluids flowing through pores deposit natural mineral cement
  • limestone - formed from seashells; mostly calcium carbonate; greyish colour; original shells mostly crushed but there are some fossilised shells
    • thermal decompostion - calcium carbonate --> calcium oxide + carbon dioxide
• Metamorphic
  • heat and pressure on sedimentary or igneous rocks over long period; mineral structure and texture differs but chemical composition is same; so long as it doesnt melt and turn to magma
  • marble is another form of calcium carbonate; high temp and prssure break down limestone and reforms as small crystals; gives marble even texture and makes it harder
• Igneous
  • formed when magma cool; contain verious different minerals randomly arranged interlocking crystals - makes them very hard
  • granite is very hard igneous rock; ideal for steps/buildings

• aluminium and iron can be extracted from their ores (useful materials are found)
• glass is made when you heat limestone, sand and soda until it melts and then cools as glass
• clay formed fromdug up weathered and decomposed rock which is soft (mouldable) until hardened by firing at high temperatures - withstand weight so good for buildings
• limestone and clay can make cement - clay contains aluminium and silicates
  • powdered clay and limestone are roasted in a rotating kiln to make mixture of calcium and aluminium silicates (cement).
  • cement mixed with water makes a slow chemical reaction turning it hard
• cement, sand, aggregate and water makes concrete
  • very quick/cheap way of constructing buildings - but is unnatractive
  • reinforced concrete - concrete and solid steel support - combines hardness of concrete and flexibility and strength of steel
• BUT quarrying uses up land and destroys habitats and costs money to make used quarries pretty again; transporting rock causes noise/pollution; disused sites are dangerous (drown in former quarries turned into deep lakes, disused mines collapse causing subsidence (big holes in railway lines etc.)

• electrolysis - splitting up with electricity
• copper immersed in liquid (electrolyte) which conductes electricty - electrolytes are free ions dissolved in water. Copper(II) sulfate solution is electrolyte in purifying copper
• electrical supply acts as an electron pump
  • pulls electrons off copper atoms at anode causing them to go into solution at Cu²⁺ ions
  • then offers electrons at cathode to nearby Cu²⁺ ions to turn them back to copper atoms
  • the impurities are dropped at anode as sludge whilst pure copper bonds to cathode
  • anode loses mass, cathode gains mass,opper dissolves awayfrom anode to cathode
• PANIC - positive anode, negative is cathode
• cathode - reduction (gains electrons) anode - oxidation (losses electrons)
• Recycling Copper:
  • cheaper to recycle then to mine and extract new copper from its ore
  • recycling copper uses 15% of energy that would be used to mine same amount
  • hard to convince people its worth the effort to sort and recycle their metal waste
    • even then you have to sort copper from all other waste meral - takes time/energy

• Alloy- mixture of 2 + different metals/ metal+non-metal - have properties that are different from metal they are made from and these new properties often make it more useful

Alloys

• Steel (carbon+Iron) - harder/stronger than iron; less likely to rust - bridges, engine parts, cars
• Brass(copper + zinc) - mixture of properties from copper and zinc but is harder - musical instruments, fittings and fixtures (e.g. screws)
• Bronze(copper + tin) - harder/stronger than tin, resistant to corrosion - springs, motor bearings, bells
• Solder(lead + tin) - no definite melting point, solidifies as it cools - solders things together
• Amalgam (mercury) - filling teeth

Smart Alloys

• Nitinol - nickel and titanium - have shape memory (bend back to original shape)
  • glasses with nitinol frames so can be bent/sat on and go back to original shape

• Iron and steel rust when they come into contact with water and oxygen (oxidation reaction)
• iron + oxygen = iron(III) oxide; water bonds to this getting hydrated iron(III) oxide
• iron + water + oxygen --> hydrated iron(III) oxide -rusting word equation
• Salt dissolved in water does not cause rusting, but it does speed it up, as does acid rain
• aluminium doesnt corrode when wet as it reacts very quickly with O2 in air getting aluminium oxide forming protective layer to aluminium below to stop further reactions

• Aluminum vs Steel Car body
  • lower density than iron or steel, lighter than the same car body made from steel - improved fuel economy
  • aluminium does not corrode easily, so corrodes less than one made from steel - last longer
  • aluminium is more expensive than steel. So a car made from aluminium is likely to be more expensive than one made from steel.

• steel - strong hammered into sheets and welded (good for body work)
• aluminium - strong/low density - engine parts to reduce weight
• glass - transparent - windows/windscreen
• plastics - light/hardwearing (electrical insulators cover wires) - internal coverings for door/dashboard
• Fibres - hard wearing - cover seats/floor (or leather but is more expensive)

Recycling

• metal from scrap car is recycled though most other materials go to landfull
• EU laws - 85% material in car MUST be recyclable
• recycling non-metal parts is difficult as have to be separated before recycled
  • takes time and energy

• Indicator is a dye that changes colour depending on pH of substance
• Universal indicator is combination of dyes that changes colour gradually (good for estimating pH) but some indicators change colour suddenly at particular pH
• very strong acid has pH 0, very strong alkali has pH 14, neutral has pH 7
• Neutralisation
• acids from H⁺ ions in water. pH is determined by concentration of H⁺ ions
• alkali is a base soluble in water. alkali forms OH- ions in water
• acid + base --> salt + water OR H⁺ + OH^-  H₂O

Other reactions of Acids

• acid + metal oxide --> salt + water
• Acid + metal hydroxide --> salt + water
• acid + carbonate --> salt + water + carbon dioxide
• Acid + ammonia --> ammonium salt

• In the Haber process, nitrogen and hydrogen react together under these conditions:
  • a high temperature - about 450ºC
  • a high pressure - 200 atmospheres
  • an iron catalyst.
• nitrogen + hydrogen ammonia OR N₂ + 3H₂ 2NH₃
•  = reversible. because its reversible you have to compromise to favour the forward reaction
  • A high pressure increases percentage yield of ammonia but high pressures are expensive
  • A high temperature gives a fast reaction but decreases the percentage yield of ammonia. - 450°C gives reasonably fast reaction with a sufficiently high percentage yield of ammonia.
  • unused hydrogen and nitrogen are recycled so nothing is wasted

iron catalyst makes reaction faster (gets to equilibrium faster) but the catalyst does not affect the position of equilibrium. without the catalyst the temp would have to be even higher to get quick enough reaction and that would reduce %yield so catalyst is important

• Price of Energy
  • energy bills low - high temp means running costs high
• Cost of raw materials
  • recycling unreacted materials
• labour costs
  • labour-intensive process = expensive; automation cuts running costs as less people; but automation is expensive initially
• plant costs (equipment)
  • depends on conditions, high pressures means higher running costs
• rate of production
  • catalysts used to make reaction faster (reduces time and costs) but catalyst can be expensive
• optimum conditions are those that give the lowest production cost
  • BUT rate of reaction and %yield must be high enough to make good amount of product per day
  • Low %yield is okay - if starting materials can be recycled

•  provide plants with 3 essential elements, nitrogen, phosphorus and potassium (NPK)
•  replace missing elements/provide more which increases crop yield as grow faster/bigger
• neutralise ammonia with acids to produce fertilisers (so can be taken in by crop roots)
  • NH₄NO₃ nitric acid = ammonium nitrate - essential nitrogen
  • (NH₄)₂SO₄ sulfuric acid = ammonium sulfate - essential nitrogen
  • (NH₄)₃PO₄ phosphoric acid = ammonium phosphate - essential nitrogen/phosphorus
  • KNO₃ nitric acid and potassium hydroxide = potassium nitrate - essential potasium/nitrogen

fertilisers are really useful - but can cause big problems

• The world population is increasing all the time, so more food has to be produced.
• Without fertilisers the yields of crops would be reduced.
• BUT, if too much fertiliser is used it can pollute water supplies.
• It may also lead to eutrophication, - where there is not enough oxygen dissolved in the water for aquatic organisms to survive.

• fertilisers put on fields and excess runs off into rivers and streams
• level of nitrates and phosphates in river increases
• algae living in river use nutriends to multiply creating algal bloom
• plants cannot photosynthesise so they have no food and die
• aerobic bacteria feed on dead plants and multiply using up oxygen in the water
• results in everything in the river dying (including fish and insects)

• Equipment:
  • a measuring cylinder to measure a particular volume of an alkali solution
  • a burette to add acid a little at a time until the alkali has been neutralised
  • a filter funnel to remove solid crystals of fertiliser after evaporating some of the water from the neutral fertiliser solution.

• Method:
  • set up apparatus, add few drops of methyl orange indicator to ammonia (turn yellow)
  • slowly add nitric acid from burette into ammonia until yellow colour turns red
    • methyl orange is yellow in alkali and red in acid, this change will signify neutralisation
  • solid ammonium nitrate crystals, evaporate solution until a little bit is left & leave to crystallise
  • crystals arent pure - if you note exactly how much nitric acid is took to neutralise, you  can repeat titration without indicator

the mass of product that you get is called the yield of a reaction

• never get 100% yield - not all reactant converted to product
• amount of product will be less than expected but still works
• more reactants at start, the higher the actual yield but %yield doesnt depend on inital reactants

• Percentage yield always between 0% -100%
• 100% means you got all expected products
• 0% means no reactants were converted to product
• the predicted yield of a reaction is just the amount of product that you would get if all the reactant converted into product