Chemistry 2.4

• Earth's structure


  • Rock
  • Gas
  • Water
• The atmosphere is made up of a mixture of gases that surrounds the earth
• Evidence used to determine the structure of the Earth

  • Earthquakes - use vibrations to figure out the density of each layer
• Layers of the Earth

  • Crust
  • Mantle
  • Outer Core
  • Inner Core
• Crust


  The thinnest layer, made of solid rock, 5-100km deep, 2 types: oceanic and continental
• Mantle


  The thickest layer, mostly solid rock called Magma, can flow easier when closer to the outer core
• Outer Core


  A dense liquid made of molten iron and nickel, responsible for the earth's magnetic field, temperatures up to 5000°C
• Inner Core


  Solid due to the pressure, made of solid iron and nickel, can reach temperatures of 6000°C
• Lithosphere


  Made up of the crust and upper mantle, a mixture of minerals, cracked into tectonic plates
• Tectonic Plates


  • In constant motion, move about 10cm a year, driven by convection currents in the mantle caused by natural radioactive processes
• Continental drift (tectonic plates) was a theory proposed by Alfred Wegener
• Evidence for continental drift


  • Some types of rocks, fossils of plants and animals found on distant continents
  • Mountain ranges and boundaries aligned when continents fitted together
• Wegener's theory was initially rejected but is now accepted due to advancements in technology
• Pangea has been moving for hundreds of millions of years
• Beliefs about tectonic plate movement

  • They move up and down
  • They move side to side
  • They are fixed in place after the Earth cooled down
• The Earth was formed about 4.5 billion years ago from pieces of rock and dust
• There was no atmosphere initially, the atmosphere developed over time
• Development of the atmosphere

  1. 4.5 billion years ago - very hot, Helium and Hydrogen present

  2. 3.5 billion years ago - volcanic activity released CO2, H2O, N2, CH4, NH3 forming the early atmosphere

  3. 3 billion years ago - oceans formed, atmosphere 40% CO2, 60% N2

  4. 2 billion years ago - plants produced oxygen, atmosphere 30% CO2, 5% O2, 65% N2

  5. 0.5 billion years ago - ozone layer formed, atmosphere 78% N2, 21% O2, 0.04% CO2
• Types of plate boundaries

  • Destructive/Convergent - plates move towards each other, denser plate subducts, causes earthquakes and volcanoes
  • Constructive/Divergent - plates move away from each other, magma rises and forms new crust
  • Conservative - plates slide past each other, can cause earthquakes
• The crust can be formed or recycled/destroyed
• In 4.5 billion years, the composition of the Earth's atmosphere has changed significantly
• Condensation


  The change of a gas into a liquid
• Fossil fuels


  Compounds containing hydrogen and carbon, formed from crushed marine animals compressed by the sea bed
• Photosynthesis


  Carbon dioxide + Water -> Glucose + Oxygen (using sunlight)
• Photosynthesis


  Caused a massive decrease in CO2 levels and increase in O2 levels
• Respiration


  Oxygen + Glucose -> Carbon dioxide + Water (to produce energy)
• Respiration


  Caused an increase in CO2 levels due to increasing population
• Combustion


  Hydrocarbon + Oxygen -> Carbon dioxide + Water
• Combustion of fossil fuels produces soot and toxic carbon monoxide
• Acid Rain


  Sulfur dioxide dissolves in water in the atmosphere to form sulfuric acid, which falls as acid rain
• Effects of Acid Rain


  • Damages metals, rocks, buildings, statues
  • Damages trees by affecting the waxy layer on leaves
  • Makes rivers and lakes too acidic for aquatic life
  • Changes the pH level of soil
• Increasing CO2 levels


  Causes more extreme weather, rising sea levels, deforestation, extinction of wildlife, temperature increase, decrease in rainfall
• Ways to decrease CO2 levels


  • Use renewable energy sources
  • Reduce deforestation
  • Develop new technologies
  • Reduce electrical demand
  • Recycle and reuse materials
  • Use mass transportation and travel less
• Greenhouse effect


  A natural process that warms the Earth's surface, caused by greenhouse gases like CO2, CH4, H2O, N2O