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Name three parts of earth's structure?
What is the earth's crust?
thin outer layer of solid rock
What is average depth of earth's crust?
What is the lithosphere?
upper part of the mantle
made up of jigsaw of tectonic plates
what is the temperature and structure of the lithosphere?
how thick is the lithosphere?
over 100km is places
What is the mantle?
The solid section between the crust and the core
What are the temperature and structure of the mantle?
near the crust = very rigid
as you go deeper... temperature increases
becomes less rigid and can slowly flow, semi liquid
How big is the earth's core?
just over half the earth's radius
Is the inner core solid or liquid?
is the outer core solid or liquid?
What creates a lot of heat inside the earth?
What is the effect of the heat of created inside of the earth?
heat creates convection currents in the mantle
these cause the plates of the lithosphere to move
What are tectonic plates?
- big rocky rafts
- float on the mantle
- less dense than the mantle
What speed do the plates move?
2.5 cm per year
What happens when plates meet?
volcanoes and earthquakes can happen
Why can't you study the inner structure of the earth?
The crust is too thick to drill through
What are seismic waves?
- 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
What are the two types of seismic waves?
How are the two types of seismic wave used?
- 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.
Who, and when, hypothesised that Africa and South America had previously been one continent?
What evidence was found for theory of continental drift?
- 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
What is the theory of continental drift?
- 300 million years ago one supercontinent
- called Pangaea
- broke into smaller chunks
- still slowly drifting apart
- based on theory of plate tectonics
Why wasn't continental drift theory accepted at first?
- 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
When did scientists investigate mid-atlantic ridge?
Mid Atlantic ridge investigation - what was found about under water mountains?
- magma (molten rock) rises up through sea floor
- roughly symmetrical either side of ridge
- suggests sea floor spreading at about 10 cm / year
Mid Atlantic ridge investigation - what was found due to magnetic orientation?
- 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
What are volcanoes?
- molten rock (magma) emerges through Earth's crust from mantle
- if pressure then violently erupts
- magma becomes lava when erupts
Oceanic and continental crusts collide - what happens?
- 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
What is igneous rock?
- 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
what effects the type of igneous rock formed?
- composition of the magma
- how quickly it cools
name two types of magma and info on them?
- 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 rhyoliteeruption is explosive. Thick lava violently blown out of the top.
How do geologists predict volcanic eruptions?
- study magma movements below the ground near to a volcano
- still unpredictable but saves lives
What are the three types of rock?
How is sedimentary rock formed?
- 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
What is limestone?
- 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
What is thermal decomposition?
When one substance chemically breaks down into at least two new substances when it is heated
What is the word equation for limestone thermal decomposition?
Calcium carbonate > calcium oxide + carbon dioxide
What is the symbol equation when limestone thermally decomposes?
CaCO3 (s) > CaO (s) + CO2 (g)
How are metamorphic rocks formed?
- 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!
What is marble?
- 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
How is igneous formed?
- when magma cools
- contain different minerals in randomly arranged interlocking crystals
- are very hard
- granite (our kitchen work top) is very hard igneous rock
Sedimentary / metamorphic / igneous..?
marble = metamorphic
granite = igneous
limestone = sedimentary
What are rocks?
usually mixture of minerals
What are ores?
are minerals we can get useful materials from.
Where do we get aluminium and iron?
extracted from their ores
How is glass made?
- heat limestone - (calcium carbonate) with sand (silicon dioxide) and soda (sodium carbonate) until it melts.
- when cools becomes glass
Tell me all about bricks and clay, its very interesting...
- 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
How is cement made?
powdered clay and powdered limestone are roasted in rotating kiln to make a complex mixture of calcium and aluminium silicates = cement.
How is cement used?
- 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
Where does copper come from?
- Dug out of the ground as a copper ore
- (like chalcopyrite or malachite)
How is copper extracted?
- Mixing ore with carbon and heating
- (this is not pure enough to use in electrical conductors)
What is electrolysis?
- means "splitting with electricity"
- using an electric current to purify
Describe the copper electrolysis process?
- 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
what acts as electron pump in electrolysis?
The electic supply
what is a cathode?
negative electrode in electrolysis
what is an anode?
positive electrode in electrolysis
What happens at the anode in copper electrolysis?
- impure copper disolves
- Cu2 ions pulled off the copper
- impurities dropped as a sludge
what happens at the cathode in copper electrolysis?
- starts as a thin piece of pure copper
- pure copper added to it as CU2 ions
What is the chemical reaction at the cathode in copper electrolysis?
Cu2+ (aq) + 2e- > Cu (s)
Reduction is the gain of electrons (removal of oxygen)
What is the chemical reaction at the anode in copper electrolysis?
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
pH scale - what is the range?
0 - 14
what are acids?
- pH 0 to 6
- 0 is very strong acid
- form H+ ions in water
- pH is determined by the concentration of H+ ions
what is a base?
Base is substance with pH greater than 7
What are alkalis?
- An alkali is a base soluble in water
- Alkalis form OH- ions in water
What is universal indicator?
combination of dyes which change colour depending on the pH of a substance
What is neutralisation?
reaction between acids and bases
acid + base to salt plus water
What is the formula for neutralisation?
H+ + OH- Both way arrow H2O
Metal Oxides and metal hydroxides
- 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?
Hydrochloric acid + copper oxide to copper chloride + water
2HCl+CuO to CuCl2 + H2O
sulphuric acid + potassium hydroxide?
sulphuric acid + potassium hydroxide to potassium sulfate + water
H2SO4 + 2KOH to K2SO4 + 2H2O
What is an alloy?
a mixture of a metal and other elements
- two or more metals like brass and bronze
- or metal and non-metal like steel
What is 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
What is brass?
- alloy of copper and zinc
- harder than either of them
What is bronze?
- Alloy of copper and tin
- much harder and stronger than tin
- more resistant to rust than copper or tin
What is solder?
- alloy usually of lead and tin
- doesn't have definite melting point
- gradually solidifies as cools down so used to solder things together
What is amalgam?
- alloy containing mercury
- used in teeth fillings
What is nitinol?
- 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
what is corrosion of iron called?
rust. (rust is only corrosion of iron not other metals)
what does iron need to contact to corrode?
What is rust?
- 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
in what environment does rusting happen more quickly?
salty or acidic
Why doesn't aluminium corrode?
- aluminium is more reactive than iron
- reacts very quickly with oxygen in the air
- forms aluminium oxide - protective layer
what advantages does aluminium have over steel for cars?
- 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
materials used in car?
- steel - stong sheets for body work
- aluminium - strong light - engine parts
- 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?
- Nitric acid + sodium hydroxide to sodium nitrate + water
- HNO3 + NaOH to NaNO3 + H2O
phosphoric acid + sodium hydroxide..?
- phosphoric acid + sodium hydroxide to sodium phosphate + water
- H3PO4 + 3NaOH to NA3PO4+ 3H2O
Acid and carbonates...
hydrochloric acid plus sodium carbonate?
- hydrochloric acid + sodium carbonate to sodium chloride + water + carbon dioxide
- 2HCl + Na2CO3 to 2NaCl + H2O + CO2
Acid and carbonates...
sulphuric acid + calcium carbonate...?
- sulphuric acid + calcium carbonate to calcium sulphate + water + carbon dioxide
- H2SO4 + CaCO3 to CaSO4 + H2O + CO2
Acids and carbonates...
phosphoric acid + sodium carbonate...?
- phosphoric acid + sodium carbonate to sodium phosphate + water + carbon dioxide
- 2H3PO4 + 3Na2CO3 to 2Na3PO4 + 3H2O + 3CO2
Acid + Ammonia to...
Hydrochloric acid + ammonia to...
- Hydrochloric acid + ammonia to ammonium chloride
- HCl + NH3 to NH4Cl
sulphuric acid + ammonia to....
- sulphuric acid + ammonia to ammonium sulfate
- H2SO4 + 2NH3 to (NH4)2SO4
nitric acid + ammonia...
- nitric acid + ammonia to ammonium nitrate
- HNO3 + NH3 to NH4NO3fertiliser
What are the three main essential elements in fertilisers?
Benefits of using fertiliser?
- 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
why is ammonium nitrate a good fertiliser?
- made by neutralising nitric acid with ammonia
- nitrogen from two sources
name three other fertilisers?
- ammonium sulphate (neutralising sulphuric acid with ammonia)
- ammonium phosphate (neutralising phosphoric acid with ammonia)
- potassium nitrate (neutralising nitric acid with potassium hydroxide)
What is eutrophication?
- 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
How do you make ammonium nitrate?
- 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
What is "yield"
- mass of product after reaction
- can never get 100% yield.
What is the process which makes ammonia from nitrogen and hydrogen and who developed it?
- The HABER process.
- German chemist, Fritz HABER
Is the Haber process reversible
What is the equation for the Haber process?
N2 + 3H2 to / from 2NH3
Where are the nitrogen and hydrogen obtained from?
- Air (78% nitrogen)
- Hydrogen - cracking of oil or natural gas
Describe the HABER process?
- 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 **
What are the five factors for the cost of a new substance?
- 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
What are the optimum conditions for 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
What is salt?
Sodium chloride NaCl
How do you get salt?
- 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)
electrolysis of brine
- 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
What four ions are sodium chloride?
Cathode reaction - brine electrolysis?
- 2H+ + 2e- to H2a reduction reaction
Anode reaction - brine electrolysis?
- 2Cl- - 2e- to Cl2
- oxidation reaction
Uses of products of the electrolysis of brine?
- 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