c1 notes

early atmosphere
- earth roughly 4 billion yrs old
- created by volcanoes erupting + releasing gases
- contained mostly co2 + water vapour
- earth cooled + water vapour condensed to form oceans
- co2 dissolved into oceans + used to form marine organism shells which were compacted to form sedimentary rock
- plants evolved to photosynthesise, takingin co2 + releasing oxygen
- scientists don't kno where all nitrogen came from bc they weren't there to record evidence but most theories suggest it ws due 2 volcanoes

atmosphere today
- nitrogen 78%
- oxygen 21%
- co2 0.04%
- argon 0.9%
- other gases v small amounts

gas levels
- co2 rises due to burning fossil fuels + deforestation
- co rises due to incomplete combustion of fossil fuels
- so2 rises due to volcanoes + burning sulfur impurities
- methane rises due to cattle waste gases
- nitrogen oxides rise due to lightning + car engines

rocks
- igneous formed when magma or lava cool to form solids
- large crystals mean the rock cooled slowly
- small crystals mean the rock cooled quickly
- eg granite

- sedimentary rock formed by layers of sediment being compacted over a long time
- eroded more easily than other kinds of rock
- can contain fossils but no crystals
- eg chalk + limestone (from calcium carbonate)

- metamorphic rock has crystals
- formed by heat + pressure on sedimentary rock
- contains interlocking crystals
- eg marble (from limestone or chalk)

quarrying limestone
- produces local jobs in rural areas + improves economy
- quarries can be landscaped after
- used 4 making cement (heated w powdered clay)
- used 4 making concrete (mix cement + sand + gravel + water)
- used 4 making glass (heated w sodium carbonate + sand)
- all used to construct buildings

- produce dust
- produce traffic
- produce noise
- destroy landscape

calcium compounds
- thermal decomposition = breaking down a substance using heat
- eg calcium carbonate → calcium oxide + carbon dioxide
- eg copper carbonate → copper oxide + carbon dioxide
- metal carbonate → metal oxide + carbon dioxide

calcium cycle
- thermal decomposition of calcium carbonate forms calcium oxide + carbon dioxide
- when water is added to the calcium oxide it fizzes and steams + forms a crumbly white solid which is calcium hydroxide
- when more water is added to the calcium hydroxide it forms a calcium hydroxide solution - limewater
- if carbon dioxide is added it becomes calcium carbonate again

- if co2 is bubbled thru limewater it will turn from clear cloudy or milky as it forms calcium carbonate

indicators
- indicators tell us whether something is an acid or an alkali
- universal indicator goes from red (acidic) to violet (alkaline) + neutral (pH 7) is green
- acids turn blue litmus paper red
- alkalis turn red litmus paper blue

neutralisation
- stomachs are acidic + have a pH of ⅔
- they produce hydrochloric acid (HCl) which kills bacteria + aids digestion
- too much acid being produced causes indigestion or heartburn
- indigestion tablets neutralise the excess acid

- neutralisation = making the pH of a substance closer or equal to 7
- 3 substances neutralise acids - metal carbonates (metal carbonate + acid → salt + water + co2) - metal oxides (metal oxide + acid → salt + water) - metal hydroxides (metal hydroxide + acid → salt + water)

- hydrochloric acid forms a chloride - sulfuric acid forms a sulfate - nitric acid forms a nitrate

- eg calcium carbonate + hydrochloric acid → calcium chloride + water + carbon dioxide

electrolysis
- electrolysis = breaking up a compound using electricity
- 2 electrodes {1 positive 1 negative}
- in electrolyte (hcl / water / salt solution etc)
- electricity causes fizzing + bubbling at each electrode

- salt solution → hydrogen + chlorine
- pure water → hydrogen + oxygen
- hydrochloric acid → hydrogen + chlorine

chlorine gas
- made by electrolysis of salt water or hcl
- kills bacteria to sterilise water
- makes bleach + cleaning products
- makes plastics like pvc
- test : damp blue litmus paper turns red then bleaches white
- toxic gas which can kill
- masks must be worn in factories

hydrogen gas
- made by electrolysis of salt water or water
- fuel for rockets + hydrogen fuel cells
- test : lit splint squeaky pop
- highly flammable so cld cause explosion at open flames

oxygen gas
- made by electrolysis of pure water
- helps ppl w breathing problems in hospital
- used in all combustion reactions
- test : relights a glowing splint

metal extraction
- ore = rock which contains rock compounds
- unreactive metals (gold/silver) r found as elements
- most metals r extracted from ores (eg bauxite)

- metals above carbon in reactivity series r most reactive so r extracted using electrolysis (potassium sodium calcium magnesium aluminium)
- metals below carbon r less reactive so r extracted by heating with carbon as it uses less energy (zinc iron lead copper)

oxidation/reduction
- oxidation : adding oxygen to a substance
- recution : removing oxygen from a substance

eg. extraction of iron from iron oxide (heated w carbon)
- iron oxide + carbon → iron + carbon dioxide
- carbon has been oxidised
- iron oxide has been reduced

eg. extraction of aluminium from aluminium oxide (thru electrolysis)
- aluminium oxide → aluminium + oyxgen
- aluminium oxide has been reduced

corrosion
- when metals corrode they react w oxygen in the air which can weaken the metals
- corrosion of iron is called rusting
- the more reactive the metal, the faster it will corrode
- aluminium has a protective layer of aluminium oxide so doesn't corrode as much as expected

recycling metals
- dont need 2 extract more metal
- not mining means no destroying landscapes
- less pollution so less co2
- less metal going into landfill sites

- time consuming + expensive to transport + sort
- uses up energy

metal properties
- good conductor of heat + electricity
- strength
- malleable
- reactivity
- density
- shiny
- magnetic

gold - used for making jewellery as it's unreactive (doesn't corrode) + shiny / used in electronic devices as it is an excellent conductor but only in small amounts as is v expensive

copper - used in electrical wiring as v good electricity conductor + low reactivity + ductile / used in water pipes as isn't poisonous + is malleable

aluminium - used to make aeroplane bodies as strong, low density (less fuel) + doesn't corrode easily due to protective layer of aluminium oxide [but is more expensive as extracted thru electrolysis]

iron / steel - used to make bridges car n machines as v strong + cheap to extract [but high density + can corrode]

alloys mixture of a metal with another metal

- steel is an alloy of iron (abt 95% iron 5% other elements like carbon) . is stronger + doesn't corrode as much
- in iron the layers of atoms can slip easily over each other making it less strong
- in steel the other elements stop the layers of iron atoms slipping over each other so it is stronger

- only 24 carat gold is pure gold but it's too soft for jewellery
- fineness of 24 carat gold = 1000
- 18 carat gold is gold alloy + 75% gold so is harder + is used in jewellery

- nitinol is an alloy of nickel + titanium
- shape-memory property (if it's bent a change in temperature will revert back to original shape)
- used in glasses frames + stents to keep open collapsed blood vessels

crude oil
- fossil fuel examples r coal, crude oil + natural gas
- crude oil is made from tiny dead plants + animals that living in the sea millions of years ago which didn't decay + got compacted @ the bottom of the sea bed
- all fossil fuels r non renewable so they will eventually run out

hydrocarbon = compound made out of only caron + hydrogen

1 carbon : methane
2 carbons : ethane
3 carbons : propane
4 carbons : butane

carbon atoms can make 4 bonds hydrogen atoms can make 1 bond

- ethanol contains an oxygen atom so is not a hydrocarbon
- crude oil is a mix of different hydrocarbon compounds
- contains impurities like sulfur

fractional distillation
- short chains = low boiling points
- long chains = high boiling point

top to bottom [short to long chains / low to high boiling points]
1. gases - cooking
2. petrol - fuel for cars
3. kerosene - fuel for planes
4. diesel oil - fuel for cars + lorries
4. fuel oil - fuel for ships
5. bitumen - roads

- gases : short chain hydrocarbons eg methane + ethane . easy 2 ignite, low boiling point, runny viscosity
- kerosene : medium length hydrocarbons . more difficult to ignite, higher boiling point, more sticky
- bitumen : long length hydrocarbons . difficult to ignite, high boiling point, thick + v sticky

combustion combusting - burning (reacting fuels with oxygen)

- complete combustion : hydrocarbon fuel + lots of oxygen react n produce co2 + water
- incomplete combustion : not enough oxygen to react completely so hydrocarbon fuel + not enough oxygen may produce either carbon (soot), carbon monoxide or co2 + water

- carbon (soot) causes lung disease + makes buildings dirty
- carbon monoxide is poisonous + reduces the amount of oxygens that red blood cells carry

acid rain water = pH 7 rainwater = pH 6.5 acid rain = pH 5.2

sulfur impurities in fossil fuels react with oxygen in the air to make carbon dioxide when the fuels r burnt sulfur + oxygen → sulfur dioxide sulfur dioxide gas dissolves in water in clouds to form acid rain

- acid rain makes lakes acidic which causes fish + trees to die
- buildings made of limestone may weather
- may increase corrosion of metals

climate change
- greenhouse effect : when the sun heats the earth, the earth absorbs the heat and radiates it back but greenhouse gases trap the heat in the atmosphere
- greenhouse gases eg co2, methane + water vapour
- they keep the earth at avg of 14c
- without them the earth wld b -18c

- the global avg temperature varies + recently it has risen
- may be due to human activity as co2 levels hav increased due to combustion of fossil fuels / methane levels have risen due to more cattle farming

reducing co2 in atmosphere
1. add iron compounds to oceans which causes plants to grow which are eaten by sea creatures which take in co2 to make their shells
2. capture co2 from powerstations + convert it into hydrocarbons

biofuels biofuel : fuel made from living things

- sugar cane is used to make ethanol to combine w petrol for car fuel
- soya bean oil or vegetable oil is used to combine with diesel for car fuel

- renewable
- carbon neutral (uses up + releases the same amount of carbon throughout the process so doesn't add co2 to atmosphere)

- forests may have to be cut down to make biofuels
- will increase food prices
- transportation of biofuels may release carbon so it isn't carbon neutral

choosing fuels TEA CUPS t : transport e : energy content a : availability c: cost u : useability (how easily does it burn) p : pollution s : storage

hydrogen fuel cells - hydrogen reacts w oxygen to make water w.out burning releasing electrical energy - to be used as an alternative fuel to petrol - doesn't use up fossil fuels - non pollutive - will need to b stored in petrol stations - 2 expensive atm

alkanes + alkenes
- alkanes (eg methane ethene propane butane) r all saturated hydrocarbons as they have single bonds
- alkenes ( eg ethene propene butene) r all unsaturated hydrocarbons as they have @ least 1 carbon to carbon double bond

alkane/alkene test : bromine water stays orange if it's an alkane and turns colourless if it's an alkene

cracking cracking = breaking down a long hydrocarbon chains into shorter, more useful alkane and alkene hydrocarbon chains

- shorter chain alkanes r used in petrol
- alkenes r used in polymerisatin to make plastics
- cracking is used to try and match supply with demand

polymerisation
- polymer : a long chain of monomers

when monomers r polymerised the carbon to carbon double bond breaks n joins to another carbon to make a chain

monomer : ethene polymer : polytheme properties : flexible + cheap uses : plastic bags

monomer : propene polymer : polypropene properties : flexible + shatterproof uses : buckets + bowls

monomer : chloroethene polymer : polychloroethene (PVC) properties : tough + longlasting uses : window frames + gutters

monomer : tetrafluoroethene polymer : polytetrafluoroethene (PTFE or teflon) properties : tough + slippery uses : non stick coating for frying pans

problems w polymers

- non biodegradable so will fill up landfill sites
- incinerating them will produce toxic gases

- recyclable polymers will reduce the need for drilling new crude oil
- biodegradable polymers will rot in landfill sites