Fossil Fuels

• World population uses energy in a variety of ways and much of it by direct combustion ro produce heat and light

  • Combustion requires a suitable fuel source typically something with large amounts of carbon
• Fossil fuels are much more energy dense than wood
• Fossil fuels - carbon-based fuels formed millions of years ago from the decay of living matter

  • decay of animals and plants which form organic matter that become covered in layers of sediment
  • the organic matter is subjected to pressure and heat after millions of years because of the layers of sediment building up
  • precise conditions and the type of animal and plant material available determine what type of fossil fuel is formed
• Coal - formed from plants
• Steps of the formation of coal:

  1. Huge forests grew covering most of the Earth
  2. The vegetation dies and is decomposed by bacteria, creating some carbon dioxide and methane
  3. Peat is formed
  4. The peat is compressed between layers of sediments and subjected to heat, squeezing out water other compounds
  5. Forms lignite (low-grade coal)
  6. Further compression of lignite forms coal
• Formation of Coal

  A) forests

  B) dies

  C) peat

  D) peat

  E) compressed

  F) sediment layers

  G) lignite

  H) compression

  I) coal

  
• Oil and natural gas - formed from sea creatures
• Steps of the formation of oil and natural gas (1):

  1. Small animals and plants die and fall to the bottom of the sea - plankton falls to the floor of the warm ocean e.g. zooplankton, phytoplankton
  2. Sediments and other inorganic materials mixes and cover their remains
  3. Decomposition only occurs in specific places where the mus is deoxygenated
  4. As the sediments buries more and start forming layers, they start to change into organic shale as the temperature and pressure increase when they get closer to the crust
• Steps of the formation of oil and natural gas (2):

  5. The heat and pressure turn the remains into crude oil and natural gas

  6. They separate and rise because of their low density through the rocks, filling in the pores

  7. The rock above the oil and gas is impervious (non-porous) so they get trapped underneath it

  8. The oil are held in porous rock so they can be accessed via drilling
• Formation of oil and natural gas

  A) small marine organisms

  B) sediment and rock

  C) impermeable

  D) porous sedimentary

  E) oil and natural gas

  F) porous sedimentary

  G) impermeable

  H) trapped oil

  I) sediment and rock

  J) trapped gas

  
• Extracting fossil fuels involves digging or drilling deep underground

  • length of time needed to create fossil fuels means that there is only a limited supply