Module 2

• 1. Crust
• 2. Mantle
• 3. Core

thin outer layer of solid rock

20 km

crust

upper part of the mantle

made up of jigsaw of tectonic plates

relatively cold

rigid

over 100km is places

The solid section between the crust and the core

near the crust = very rigid

as you go deeper... temperature increases

becomes less rigid and can slowly flow, semi liquid

just over half the earth's radius

solid

liquid

Radioactive decay

heat creates convection currents in the mantle

these cause the plates of the lithosphere to move

• big rocky rafts
• float on the mantle
• less dense than the mantle

2.5 cm per year

volcanoes and earthquakes can happen

The crust is too thick to drill through

• used by scientists to study earth's structure
• they are shock waves
• produced by earthquakes or man-made explosions on earth's surface
• measure time for waves to travel and where they are detected draw conclusions about structure

• P-waves
• S-waves

• S-waves travel through solids but not liquid.
• S-waves travel through the mantle.
• Mantle is therefore solid.
• S-waves do not travel through core (not seen in core's shadow).
• Therefore outer core must be liquid.
• P-waves travel faster through the middle of the core therefore suggests inner core is solid.

• Alfred Wegener
• 1914

• matching layers in rocks in different continents
• similar earthworms in South America and Africa
• observations not previously explained inc
• fossils of very similar plants and animals
• coastline of Africa and S America seem to fit together
• fossils of sea creatures in alps

• 300 million years ago one supercontinent
• called Pangaea
• broke into smaller chunks
• still slowly drifting apart
• based on theory of plate tectonics

• was big change
• movement wasn't detectable
• said caused tidal forces and earths rotation which was shown by other geologists as impossible
• It did explain things which couldn't be explained by land bridge theory (continents linked by land bridges which have sunk) such as mountains - continental drift says due to continents smashing into each other

1960s

• magma (molten rock) rises up through sea floor
• solidifies
• roughly symmetrical either side of ridge
• suggests sea floor spreading at about 10 cm / year

• iron particles align themselves with Earth's magnetic field
• as cool set in position
• every half million years earth's magnetic field swaps direction.
• rock either side has bands of alternate magnetic polarity
• proved sea floor created as continents moving apart

• molten rock (magma) emerges through Earth's crust from mantle
• if pressure then violently erupts
• magma becomes lava when erupts

• crust of ocean floor is denser than crust below continents
• two tectonic plates collide - a dense oceanic plate will be forced underneath a less dense continental.  
• This is called subduction.
• Oceanic crust tends to be cooler at the edges of a tectonic plate - so edges sink easily pulling the oceanic plate down.
• As oceanic crust forced down it melts and starts to rise.  
• if this molten rock finds way to surface volcanoes form

• made from any sort of molten rock cooling down and solidifies
• I think its a funny word
• lots of rocks on earth surface formed this way

• composition of the magma
• how quickly it cools

• iron rich basalt
• lava from eruption is runny.   Fairly safe (as safe as you can be with molten rock at 1200 degrees C!)
• silica-rich rhyolite
• eruption is explosive.  Thick lava violently blown out of the top.

• study magma movements below the ground near to a volcano
• still unpredictable but saves lives

• sedimentary
• metamorphic
• igneous

• Layers of sediment laid down in lakes or seas
• Millions of years, layers get buried under more layers and the weight pressing down squeezes out the water
• Fluids flowing through the pours deposit natural mineral cement

• A sedimentary rock
• Mostly formed from seashells
• Mostly calcium carbonate
• Grey/white in colour
• Most shells crushed, but still quite a few fossilised shells too

When one substance chemically breaks down into at least two new substances when it is heated

Calcium carbonate > calcium oxide + carbon dioxide

CaCO₃ (s) > CaO (s) + CO₂ (g)

• action of heat and pressure on sedimentary, or igneous rocks over long periods of time
• mineral structure / texture may vary but the chemical structure is often the same.
• * as long as dont melt - if melt and turn to magma they are gone!

• a form of calcium carbonate
• very high temperature and pressure break down limestone and reforms as small crystals
• makes it harder and more even texture

• when magma cools
• contain different minerals in randomly arranged interlocking crystals
• are very hard
• granite (our kitchen work top) is very hard igneous rock

marble = metamorphic

granite = igneous

limestone = sedimentary

usually mixture of minerals

are minerals we can get useful materials from.

extracted from their ores

• heat limestone - (calcium carbonate) with sand (silicon dioxide) and soda (sodium carbonate) until it melts.
• when cools becomes glass

• clay is mineral formed from weathered and decomposed rock.
• soft when dug up from  ground
• easy to mould into bricks
• can be hardened by firing at very high temperatures
• can withstand weight

• aluminium
• silicates

powdered clay and powdered limestone are roasted in rotating kiln to make a complex mixture of calcium and aluminium silicates = cement.

• mixed with water for a slow chemical reaction to set hard.
• mix with sand, aggregate (gravelly stuff) and water to make concrete.
• Reinforced concrete is composite material.  Its combination of concrete and solid steel support.  Hardness of concrete + flexibility/ strength of steel

• extraction of rocks
• uses up land
• destroys habitats
• costs money to make sites pretty afterwards
• transporting causes noise and pollution
• quarrying causes dust and noise - use dynamite
• disused sites dangerous - every year people drown in deep lakes left behind
• disused mines collapse causing subsidence

• Dug out of the ground as a copper ore
• (like chalcopyrite or malachite)

• Mixing ore with carbon and heating
• (this is not pure enough to use in electrical conductors)

• means "splitting with electricity"
• using an electric current to purify

• copper immersed in liquid which conducts electricity (electrolyte)
• for copper - Copper (II) sulphate solution used, it contains Cu²⁺ ions.
• impure copper is the anode
• current pass through electrolyte
• pure copper deposited on cathode

The electic supply

negative electrode in electrolysis

positive electrode in electrolysis

• impure copper disolves
• Cu² ions pulled off the copper
• impurities dropped as a sludge

• starts as a thin piece of pure copper
• pure copper added to it as CU² ions

Cu²⁺ _(aq) + 2e^-   >  Cu _(s)

Reduction is the gain of electrons (removal of oxygen)

Cu _(s) > Cu²⁺ _(aq) + 2e-

Oxidation is the loss of electrons (or the addition of oxygen)

• cheaper than mining and extracting from ore
• uses only 15% of the energy of mining / extraction
• hard to convince people  worth effort to sort etc

0 - 14

• pH 0 to 6
• 0 is very strong acid
• form H⁺ ions in water
• pH is determined by the concentration of H+ ions

7

Base is substance with pH greater than 7

• An alkali is a base soluble in water
• Alkalis form OH^- ions in water

combination of dyes which change colour depending on the pH of a substance

reaction between acids and bases

acid + base  to salt plus water

H⁺ + OH^-    Both way arrow H₂O

reversible equation

• metal oxides and metal hydroxides are bases
• some dissolve in water
• these soluble compounds are alkalis
• even bases that won't dissolve with still react with acids
• so all metal oxides and metal hydroxides react with acids to form a salt and water

Hydrochloric acid + copper oxide to copper chloride + water

2HCl+CuO to CuCl₂ + H₂O

sulphuric acid + potassium hydroxide to potassium sulfate + water

H₂SO₄ + 2KOH to K₂SO₄ + 2H₂O

a mixture of a metal and other elements

• two or more metals like brass and bronze
• or metal and non-metal like steel

• alloy of iron and carbon
• harder than iron
• stronger than iron (as long as carbon does not get larger than about 1%)
• iron rusts quickly, add small amount of carbon to make steel and much less likely to rust
• used for girders, bridges, engine parts, cutlery, ships, drill bits, cars

• alloy of copper and zinc
• harder than either of them

• Alloy of copper and tin
• much harder and stronger than tin
• more resistant to rust than copper or tin

• alloy usually of lead and tin
• doesn't have definite melting point
• gradually solidifies as cools down so used to solder things together

• alloy containing mercury
• used in teeth fillings

• family of alloys of nickel and titanium which remember their shape even if bent or twisted
• used in spectacles frames to survive being sat on

rust.  (rust is only corrosion of iron not other metals)

• Both of-
• oxygen
• water

• iron gains oxygen to form iron (III) oxide
• water bonds to it
• forms hydrated iron (III) oxide = rust

iron+oxygen+water to hydrated iron (III) oxide

salty or acidic

• aluminium is more reactive than iron
• reacts very quickly with oxygen in the air
• forms aluminium oxide - protective layer

• aluminium is lower density so lighter (better fuel economy)
• corrodes less so longer life
• BUT aluminium is more expensive so steel tends to be used

• steel - stong sheets for body work
• aluminium  - strong light - engine parts
• glass
• plastic - light, hard wearing, interior, electrical insulation
• fibres (natural and man-made) hardwearing seats / floor

• metal recycled but most of rest goes to landfill
• European laws say 85% materials in car must be recyclable
• by 2015 rising to 95%
• hard to sort materials

• Nitric acid + sodium hydroxide to sodium nitrate + water
• HNO₃ + NaOH to NaNO₃ + H₂O

• phosphoric acid + sodium hydroxide to sodium phosphate + water
• H₃PO₄ + 3NaOH to NA₃PO₄+ 3H₂O

• hydrochloric acid + sodium carbonate to sodium chloride + water + carbon dioxide
• 2HCl + Na₂CO₃ to 2NaCl + H₂O + CO₂

• sulphuric acid + calcium carbonate to calcium sulphate + water + carbon dioxide
• H₂SO₄ + CaCO₃ to CaSO₄ + H₂O + CO₂

• phosphoric acid + sodium carbonate to sodium phosphate + water + carbon dioxide
• 2H₃PO₄ + 3Na₂CO₃ to 2Na₃PO₄ + 3H₂O + 3CO₂

Ammonium salt

• Hydrochloric acid + ammonia to ammonium chloride
• HCl + NH₃ to NH₄Cl

• sulphuric acid + ammonia to ammonium sulfate
• H₂SO₄ + 2NH₃ to (NH₄)₂SO₄

• nitric acid + ammonia to ammonium nitrate
• HNO₃ + NH₃ to NH₄NO₃
• fertiliser

• nitrogen
• phosphorus
• potassium

• replace missing elements or provide more
• increase crop yield
• grow faster and bigger
• e.g. fertilisers add more nitrogen to plant protein which makes plants grow faster
• fertiliser must dissolve in water to reach roots

• is a base
• can be neutralised by acids to make ammonium salts
• is a key ingredient of many fertilisers

• made by neutralising nitric acid with ammonia
• nitrogen from two sources

• ammonium sulphate (neutralising sulphuric acid with ammonia)
• ammonium phosphate (neutralising phosphoric acid with ammonia)
• potassium nitrate (neutralising nitric acid with potassium hydroxide)

• fertiliser runs off fields
• into rivers and streams
• rises levels of nitrates and phosphates
• these feed algae
• multiply rapidly
• creates algae bloom (carpet of algae near surface)
• blocks light to plants below
• these die as cannot photosynthesise
• aerobic bacteria feed off dead plants and multiply using all oxygen
• kills fish and insects

• add few drops of methyl orange indicator to ammonia to turn it yellow
• slowly add nitrate acid from a burette until yellow just changes to red
• methyl orange is yellow in alkalis and red in acids  so colour change means all ammonia has been neutralised and you have ammonium nitrate solution
• gently evaporate and leave to crystallise
• repeat process with same quantities but without methyl orange to obtain pure ammonium nitrate crystals

• mass of product after reaction
• can never get 100% yield.

• The HABER process.
• German chemist, Fritz HABER

yes

N2 + 3H2 to / from 2NH₃

• Air (78% nitrogen)
• Hydrogen - cracking of oil or natural gas

• pressure set at 200 atmospheres
• H₂ and N₂ mixed in the ratio 3:1
• 450 degrees C is the optimum temp
• iron is used as a catalyst
• ** see diagram in book **

• 1 Price of energy (high temp expensive)
• 2 cost of raw materials (kept down by recycling unused materials)
• 3 labour costs
• 4 equipment costs
• 5 rate of production

• lowest production cost per kg
• however rate of production and percentage yield must be high enough to make a sufficient amount of product each day
• low yield ok as long as starting materials can be recycled

Sodium chloride NaCl

• in hot countries - sea water poured into big open tanks for sun to evaporate water leaving salt behind.
• In Britain  - extracted from underground deposits left millions years ago when ancient seas evaporated - huge deposits of rock salt under Cheshire.
• Or pumping hot water underground (solution mining)

• Brine = sodium chloride solution
• electrodes are inert
• hydrogen gas given off at cathode (-ve)
• chlorine gas is given off at anode (+ve)
• sodium hydroxide (NaOH) formed from ions left in solution

• Na+
• OH^-
• Cl^-
• H⁺

• 2H⁺ + 2e^-   to H₂
• a reduction reaction

• 2Cl^- - 2e^- to Cl₂
• oxidation reaction

• hydrogen used to make ammonia (Haber process)
• hydrogen used to make margarine
• chlorine used to disinfect water, plastics (PVC),solvents or hydrochloric acid
• sodium hydroxide used to make soap or reacted with chlorine to make household bleach