topic 8

• crude oil

  • a complex mix of hydrocarbons
  • contains molecules in which carbon atoms are in chains or rings
  • important source of useful substances ( fuel and feedstock ( raw material ) for petrochemical industry )
  • a finite resource
• formation of crude oil

  • plants and animals in the sea dies - sink to the bottom
  • over millions of years remains are buried by sediment , preventing entry of oxygen , cannot decay
  • more sediment build up on top of remains , heat and pressure is increased - crude oil or natural gas are formed gradually
• crude oil fractions

  • top to bottom
  • top - small molecules -low boiling point , very volatile , flows easily , ignites easily
  • bottom - large molecules - high boiling point , not very volatile , does not flow easily
• crude oil fractions - uses

  • top to bottom
  • refinery gas - bottled gas
  • gasoline - fuel for cars
  • kerosene - aircraft fuel
  • diesel - fuel for cars , lorries , buses
  • fuel oil - fuel for ship power station
  • bitumen -bitumen for roads and roofs
• uses of crude oil fractions

  • fractions are mostly part of the alkane homologous series
  • same general formula of CnH2n+2
  • differ by CH2
  • show gradual variation in physical properties
  • similar chemical properties
• complete combustions

  • when hydrocarbon reacts with oxygen
  • all hydrocarbon is used up and only products are carbon dioxide and water
  • ex - methane + oxygen -> carbon dioxide + water
• detecting products of a complete combustion

  • lime water turns cloudy when co2 is bubbled through it
  • anhydrous copper turns white to blue in the presence of water
• incomplete combustions

  • not enough oxygen for carbon dioxide to form
  • carbon monoxide or solid carbon formed
  • methane + oxygen -> carbon monoxide + water
  • methane + oxygen -> carbon + water
• carbon monoxide problems

  • odourless , colourless , toxic gas
  • binds to haemoglobin - restricting oxygen carrying capacity
  • leading to carbon monoxide poisoning
• soot problems

  • produced in appliances such as boiler , can clog up pipes carrying waste gas away
  • soot also produced by vehicles - breathing can caused lung disease - bad for people with asthma
  • leaves black marks on buildings and walls
• acid rain

  • causes of acid rain :
  • hydrocarbons contain sulfur impurities
  • when fuels are burnt , sulfur reacts with oxygen from air to form sulfur dioxide gas
  • sulfur dioxide dissolves in rain water - > lowers ph , forming acid rain
  • water + sulfur dioxide -> sulphurous acid
  • sulphurous acid + oxygen -> sulfuric acid
• effects of acid rain

  • makes river , lakes and soil more acidic > harming organisms that live there
  • damages trees
  • speeds up weathering of buildings / statues made of limestone or marble and corrosion of metal
  • CAWCS
  • calcium carbonate + sulfuric acid > calcium sulfate + water + carbon dioxide
• CAWCS

  • Calcium carbonate ( C ) + sulfuric acid ( A ) -> calcium sulfate + water + carbon
• solutions for acid rain

  • reducing amount of sulfur in petrol , diesel and fuel oil
  • removing acidic gases from power station - neutralising with a base such as calcium carbonate
• oxides of nitrogen

  • when temperatures are high enough in car engine
  • nitrogen and oxygen in air react forming many oxides of nitrogen
  • which are pollutants
  • nitrogen dioxide is a toxic red-brown gas - can cause respiratory diseases
  • catalytic converters convert these into harmless nitrogen
  • 2NO2 -> N2 + 2O2
• cracking

  • the process of breaking down of longer hydrocarbons into shorter and more useful hydrocarbons
  • most cases - long chain of alkane is thermally decomposed into shorter chains
  • shorter chains of alkanes are used as fuels
  • shorter chains of alkenes are used for making plastics
  • ALKANES are SATURATED - carbons bonded by single bond
  • ALKENES are UNSATURATED - carbons are joined by double bonds
• the need of cracking

  • separates crude oil into shorter fractions
  • theses shorter fractions are at higher demand
  • meeting demand
• what makes a good fuel

  • does not produce harmful gases
  • burns easily - however can be dangerous
  • energy efficient - small amount of it produces a lot of energy
  • easy to store and transport - eg coal , however gases fuels bust be at high pressure to store
• using hydrogen as a fuel

  advantages of using hydrogen vs petrol

  • hydrogen fuel is renewable , petrol is non - renewable
  • hydrogen is less polluting
  • water is the only waste product

  disadvantages of using hydrogen vs petrol

  • more expensive - requires electricity to produce
  • hydrogen is less safe - more flammable , is a gas - more prone to gas leaks
  • more difficult to store
  • fewer gas stations where you can fill up hydrogen fuel
• The early atmosphere

  • mainly carbon dioxide
  • smaller amounts of water vapour and other gases
  • little to no oxygen
• evidence for early atmosphere

  • scientist studied volcanoes - release a lot of gas
  • conflicting evidence
  • atmosphere of venus and mars are mainly carbon dioxide
  • atmosphere of titan , one of Saturns moons , is 98% nitrogen
• oxygen

  • little to no oxygen

  evidence

  • volcanoes do not release oxygen
  • iron compounds found in earths oldest rocks only formed in the absence of oxygen
  • only around 2.4 billions years ago , rocks containing bands of iron oxides started to form
  • this oxidation of iron suggest that oxygen levels have increased at this time
• oceans

  • started to form as earth temperature decreased
  • water vapour condensed into liquid water - forming oceans
• changing atmosphere

  • oxygen increases , carbon dioxide decreased
  • carbon dioxide decreased due to :
  • carbon dioxide dissolving in oceans
  • marine organisms use carbon dioxide to make shells of calcium carbonate - over time became sedimentary rocks
  • photosynthesis - first organisms - cyanobacteria , photosynthesised releasing oxygen into atmosphere
• atmosphere today

  • 78 % - nitrogen
  • 21 % - oxygen
  • other 0.9 % - argon , 0.04 % carbon dioxide
• oxygen practicals - 1 - metal oxides

  aim : to investigate amount of oxygen in the atmosphere

  1. iron wool into bottom of measuring cylinder
  2. measuring cylinder placed upside down into water , secured with clamp
  3. metal reacts with oxygen in air , volume of air decreases , water will move up into tube
  4. use ruler to measure the final level of water
  5. can determine amount of oxygen used by comparing the level of water from beginning and end
• oxygen practical - 2- non metal oxides

  1. plastic plate with phosphorus is floated in water tank
  2. bell jar is placed on water around floating phosphorus
  3. use ruler to measure initial water level line
  4. phosphorus will react with oxygen - pressure decreases , water level will increase
  5. after 24 hours use ruler to measure final water level
  6. determine amount of oxygen used compared to initial and final water level
• oxygen practical - 3 - non metal oxide

  1. copper wool placed inside glass tube - connected to two gas syringes
  2. initial volume left in syringe is 100cm3 in one of the syringes
  3. tube is heated by bunsen burner flame - copper oxide is formed
  4. gas syringe constantly passes air through copper to allow reaction to complete
  5. at the end measure final volume of air left in syringe
• greenhouse gas effect

  • solar radiation emitted from sun passes through clear atmosphere - most radiation absorbed by earths surface , warms earth
  • some radiation reflected by earth and the atmosphere
  • some infrared radiation passes through atmosphere , remitted in all directions by greenhouse gas molecules
  • warming the earths surface - increases global temperature
  • gases in the atmosphere that absorb the energy are called GREEN HOUSE GASES
• correlation and climate change

  • carbon dioxide levels have risen dramatically since 1850
  • as carbon dioxide levels have increased so has average temperature of earths surface
  • having a strong correlation , however correlation does not mean causation
  • to show causation scientists have collected evidence
• evidence of climate change

  • satellite evidence data confirms that CO2 levels have increases , reduction in infrared waves leaving atmosphere
  • temperature records - dating back to 1659 - may not be accurate
  • ice core data- information about trapped gas 800,000 years ago
• potential climate change risks

  • health - infectious diseases , air quality - respiratory illness
  • agriculture impacts - crop yield
  • forrest impacts -Forrest fires
  • water - water quality , change in water supply , competition for water
  • coastal area - erosion of beaches , low lying land
  • nature - loss of animal habitats ,extinctions
• limiting the impacts of climate change

  • using renewable resources - reducing greenhouse gas production
  • building flood defenses, dams , irrigation systems
  • landfill methane captures