Fuels and Earth Science

• How can the effects of global warming be mitigated?

  • Construct flood defences in areas of low lying land
  • Use of irrigation systems to provide water in drought
  • Produce alternative crops which are better adapted to the new environment
• How has human activity increased the amount of methane in the atmosphere?

  • Raising livestock such as cows

  • Decay of organic waste in landfill sites
• What are the effects of global warming?

  • Melting of polar ice caps
  • Difficulties acquiring drinking water
  • Flooding
  • Forest fires
  • Destruction of ecosystems
• What is the current composition of Earth's atmosphere?

  • Nitrogen - 78%

  • Oxygen - 21%

  • Argon - 0.93%

  • Carbon - 0.04%
• Evaluate the evidence that human activity is causing climate change

  • There is a correlation between carbon dioxide concentration in the atmosphere, fossil fuel consumption and temperature change

  • Correlation doesn't mean causation

  • There may be uncertainties in the data (e.g. location of the measurements and historical accuracy)
• How has human activity increased atmospheric carbon dioxide concentration?

  • Burning fossil fuels for energy releases carbon dioxide

  • Deforestation reduces the amount of photosynthesis occurring so less carbon dioxide is converted to oxygen
• What is the greenhouse effect?

  • Electromagnetic radiation from the sun passes through the Earth's atmosphere

  • The Earth absorbs some radiation and warms up

  • Heat is radiated from the Earth as infrared radiation

  • Some of the infrared radiation is absorbed by greenhouse gases in the atmosphere which warms the atmosphere
• What are greenhouse gases?

  Various gases in the atmosphere (such as carbon dioxide, methane and water vapour) that absorb the heat radiated from Earth
• What is the chemical test for oxygen?

  • Insert a glowing splint into a test tube of gas.

  • If oxygen is present, the splint will ignite
• How did the amount of oxygen in the early Earth's atmosphere increase?

  • The growth of early plants used carbon dioxide for photosynthesis and released oxygen

  • This increased the amount of oxygen and decreased the amount of carbon dioxide in the atmosphere
• How did the amount of carbon dioxide in the atmosphere decrease after oceans formed?

  Carbon dioxide dissolved into the oceans so the amount of carbon dioxide in the atmosphere decreased
• How did oceans initially form?

  Condensation of water vapour
• What was the Earth's early atmosphere thought to contain?

  • Little or no oxygen
  • Large amount of carbon dioxide
  • Water vapour
  • Small amounts of other gases
• Describe how Earth's early atmosphere formed

  • Initially, the Earth's surface was molten with no atmosphere
  • Cooling caused land masses to solidify
  • Volcanoes formed on the land masses and released gases which formed the early atmosphere
• What produced the gases that formed Earth's early atmosphere?

  Volcanic activity
• Why is cracking necessary?

  The demand for shorter chain alkenes and alkanes is much greater than the demand for long chain alkanes
• What type of reaction is cracking?

  Thermal decomposition
• What do the terms saturated and unsaturated mean?

  • Saturated - only contains single bonds

  • Unsaturated - contains some C=C

  double bonds
• What is cracking?

  • Breaking down large hydrocarbons into smaller more useful ones

  • Saturated alkanes are cracked into shorter chain alkanes and short chain unsaturated alkenes
• Are petrol, kerosene and diesel renewable fuels?

  • No, they are non-renewable.

  • They are finite resources which are not being readily replaced
• Name the non-renewable fossil fuel found in natural gas

  Methane
• What are the disadvantages of using hydrogen as a fuel in cars?

  • It is expensive to produce and a lot of energy is required for the electrolysis of water to acquire the hydrogen
  • Difficult and dangerous to store hydrogen because it is very volatile and easily ignites
• What are the advantages of using hydrogen as a fuel in cars?

  • It releases more energy per kg compared to most other fuels
  • Water is the only product so no pollutants
  • Renewable source as hydrogen can be extracted from water
• What problems are associated with oxides of nitrogen?

  • Pollutants
  • Produce acid rain with similar effects as SO2
  • Cause respiratory problems
• How are oxides of nitrogen produced from car engines?

  The high temperature and pressure of a car engine causes nitrogen and oxygen from the air to react together
• What problems can acid rain cause?

  • Corrodes buildings and statues made of limestone
  • Kills/damages the vegetation
  • Lowers the ph of large bodies of water, killing the wildlife
• How is acid rain produced?

  • Sulfur dioxide (produced when combusting impure hydrocarbon fuels) evaporates into the air

  • It reacts with water in the clouds to form sulfuric acid

  • This is 'acid rain'
• Why is sulfur dioxide sometimes produced when burning hydrocarbon fuels?

  • Some hydrocarbon fuels contain sulfur impurities

  • When the fuel is burned, the sulfur reacts with oxygen to form sulfur dioxide
• What are the problems with incomplete combustion?

  • Produces carbon monoxide which is toxic and can be fatal if breathed in
  • Produces carbon particulates (soot) which cause global dimming and respiratory problems
• What are the problems with carbon monoxide?

  • Carbon monoxide is a toxic gas

  • It is colourless and odourless and if breathed in can cause death by preventing the red blood cells from carrying oxygen around the body
• What are the products of incomplete combustion?

  • Carbon particulates - soot

  • Carbon monoxide

  • Water
• When does incomplete combustion occur? What is required to ensure complete combustion occurs?

  • Incomplete combustion occurs when there is an insufficient supply of oxygen

  • To ensure complete combustion occurs, the reaction should be carried out with excess oxygen
• True or false? Energy is given out when a fuel undergoes complete combustion

  • TRUE

  • The reaction is exothermic
• What are the only products when a hydrocarbon fuel undergoes complete combustion?

  Water and carbon dioxide
• Products from crude oil mostly belong to which homologous series?

  Alkane homologous series
• What is a homologous series?

  Series of compounds which :

  • Have the same general formula
  • Have similar chemical properties
  • Differ by CH2 in molecular formula form neighbouring molecules
  • Slight variation in physical properties
• What are the properties of hydrocarbons that are tapped from the top of the fractionating column, like petrol and refinery gas?

  • Low boiling point
  • Highly volatile
  • Easily ignited
  • Shorter carbon chains (small molecules)
• Where in the fractionating column do hydrocarbons with the highest viscosity condense?

  • Viscosity is how thick and sticky a substance is

  • The hydrocarbons with the highest viscosity (like bitumen) are collected at the bottom of the fractionating column
• How do the hydrocarbons at each faction differ?

  • Boiling points
  • Ease of ignition
  • Viscosity
  • The number of hydrogen and carbon atoms their molecules have
• Fuel oil is a fraction of crude oil. What is it commonly used for?

  Fuel for large ships and in some power stations