Fuels and Earth Science

• What is crude oil?

  A complex mixture of hydrocarbons, contains molecules with rings of chains or carbon atoms, source of fuel and feedstocks for the petrochemical industry, finite natural resource.
• Why is crude oil separated?

  It isn’t very useful by itself, but its separated products are.
• Refinery gas is used for heating and cooking.


  Kerosene is used as aircraft fuel.
• Bitumen is used for road surfacing and roofs.


  Fuel oil is used for some power stations and large ships.
• How so hydrocarbons differ at each factions?

  Boiling points, ease of ignition, viscosity, number of hydrogen and carbon atoms
• Properties of hydrocarbons at the top of the column.

  Low boiling points, short carbon chain, highly volatile, easily ignited
• What is a homologous series?

  Have the same general formula, similar chemical properties but slight variation in physical ones, differ by CH2 from neighbouring molecules.
• Only products when hydrocarbon fuel undergoes complete combustion.

  Water and carbon dioxide.
• Complete combustion is exothermic.

  Complete combustion of ethane:

  2C2H6 + 7O2 - 4CO2 + 6H20
• Products of incomplete combustion.

  Carbon particulates/soot (C), Carbon monoxide, water
• Incomplete combustion of methane.

  2CH4 + 3O2 - 2CO + 4H20
• Why is sulfur dioxide sometimes produced when burning hydrocarbon fuels?

  Some hydrocarbon fuel contain sulfur impurities which sulfur reacts with oxygen.
• How is acid rain produced?

  Sulfur dioxide produced by combustion of impure hydrocarbon fuels evaporates into the air and reacts with water to form sulfuric acid.
• How are oxides of nitrogen produced from car engines?

  High temperature and pressure causes nitrogen and oxygen from the air to react.
• Problems with oxides of nitrogen.

  Pollutants, produce acid rain, cause respiratory problems
• Hydrogen as fuel in cars.

  Releases more energy per kg, water is the only product, renewable source as it can be extracted from water. Expensive to produce as energy required for electrolysis, difficult and dangerous to store as it ignites easily.
• What is cracking?

  Breaking down large hydrocarbons into smaller more useful ones, saturated alkanes are cracked into shorter chain alkanes and unsaturated alkenes.
• Saturated - only contains single bonds.


  Unsaturated - contains some C=C double bonds.
• What type of reaction is cracking?

  Thermal decomposition.
• Why is cracking necessary?

  Higher demand for shorter chain alkanes/alkenes than long chain alkanes.
• What formed the Earth’s early atmosphere?

  Earth surface was initially molten with no atmosphere, cooling caused land masses to solidify and formed volcanoes, volcanic activity released gases.
• Earth’s early atmosphere.

  Little or no oxygen, lots of carbon dioxide, water vapour, small amounts of other gases.
• How did the amount of carbon dioxide decrease after oceans formed (when water vapour condensed)?

  It dissolved into the oceans.
• How did the amount of oxygen in Earth’s early atmosphere increase?

  Plants used carbon dioxide and released oxygen during photosynthesis.
• Greenhouse effect.

  Electromagnetic radiation from the sun passes through the earth’s atmosphere, some absorbed by the earth and then radiated, some of this infrared radiation is absorbed by greenhouse gases in the atmosphere which warms it.
• Current composition of Earth’s atmosphere.

  78% nitrogen

  21% oxygen

  0.93% argon

  0.04% carbon
• Evaluate the evidence that human activity is causing climate change.

  There is a correlation between carbon dioxide concentration and the atmosphere, fossil fuel consumption and temperature change - correlation doesn’t mean causation and there my be uncertainties in the data (e.g. location of the measurements).
• Effects of global warming.

  Polar ice caps melting, difficulties acquiring drinking water, flooding, forest fires, destruction of ecosystems
• How has methane increased from human activities?

  Raising livestock such as cows, decay of organic waste in landfill sites.
• How can the effects of global warming be mitigated?

  Construction of flood defences, use of irrigation systems, producing alternative crops better adapted to the new environment.