c6.12 and 3

• extracting aluminium


  • aluminium has low density
  • extracted from the compound, aluminium oxide by electrolysis
  • Aluminium ion (Al3) and oxide ion (02-)
  • high melting point, 2000degrees
• electrolysis of aluminium


  1. the compound must be made molten for the ions to move freely.
  2. It is then mixed with cryolite which lowers melting point
  3. this reduces amount of energy needed and saves money
• electrolysis of aluminium oxide

  
• • cathode and anode both are made of graphite(carbon)
  • good conducter of electricity
  • high melting point used for high temperature
• reduction reaction: Al3+ + 3e- =>Al

  • each ion gains 3 electrons and forms an aluminium atom

  oxidation reaction: O2- => O+2e-

  • loses electrons to form an oxygen atom
• • anode must be replaced regularly, oxygen molecules produced at anode reacts with graphite carbon forming Co2 gas
• • cons of it being expensive-
  • melting aluminum oxide requires alot of energy and alot of the energy is required to produce electricity
• low grade ores contain only a very small amount of copper- harder to extract the copper economically from there ores
• bioleaching


  • uses bacteria

  1. the bacteria carry out chemical reactions and they produce a solution called leachate( contains the metal compound)
  2. at the end of both phytomining and bioleaching, the metal compound that we want has been extracted from the low-grade ore. We now need to extract the metal from the compound
• both phytomining and bioleaching allow us to economically extract metal from the low grade ores
• earths resource of metals are limited
• the methods dont involve digging ,transporting and disposig large amount of rock unlike in traditional mining
• -bioleaching doesnt release harmul sulfur dioxide into the atmosphere

  • cheaper
  • slow
  • toxic substances are sometimes produced
  • it allows metal to be extracted from ores that contain too little metal for traditional methods to be profitable
• phytomining


  • plants growing on contaminated land asborb copper ions as they grow.
  • these plants are then harvested and burned, producing ash that contains high concentration of copper compound
• bioleaching


  • bacteria is mixed with low-grade ores
  • the bacteria converts the copper into a solution rich in copper compound called leachate solution
  • Disadvatage- process is very slow
• • bioleaching allows for the extraction of copper from low-grade ores
  • phytomining allows for the extraction of copper from contaminated land
• fractional distillation


  • process of separating crude oil into group of hydrocarbons with similar numbers of carbon atoms.
  • hydrocarbons with few carbon atoms are called 'short-chain hydrocarbon'
  • hydrocarbon with lots of carbon atom are called long-chain hydrocarbon
• What are the products of complete combustion of hydrocarbons?


  Carbon dioxide and water
• What is the environmental impact of particulates?


  They form smog and cause global dimming
• How does reverse osmosis work?


  Salty water passes through a membrane allowing only water molecules
• What is the difference between global warming and climate change?


  Global warming is Earth's rising average temperature.
• What role does the atmosphere play for Earth?


  It acts as a protective layer of gases.
• How does the greenhouse effect maintain Earth's temperature?


  It traps heat energy close to Earth.
• What type of radiation does the sun emit towards Earth?


  Short-wavelength radiation.
• What happens to solar energy when it reaches Earth's surface?


  Some energy is absorbed, some is re-emitted.
• What are greenhouse gases?


  Gases that absorb and re-emit heat energy.
• Name three greenhouse gases.


  Carbon dioxide, methane, water vapor.
• What are the two main reasons for rising carbon dioxide levels?


  Burning fossil fuels and deforestation.
• How do farm animals contribute to methane emissions?

  They produce methane during digestion.
• What is deforestation's impact on carbon dioxide levels?


  It reduces photosynthesis, increasing CO₂.
• What are some consequences of global warming?


  Increased frequency of extreme weather events.
• How does global warming lead to sea level rise?


  Melting ice and thermal expansion of water.
• What are the two mechanisms of sea level rise?


  Ice melting and water expansion.
• What happens to ocean water as temperatures rise?


  Water expands, increasing ocean volume.
• How does climate change affect biodiversity?

  Species may not adapt or migrate fast enough.
• What is the greenhouse effect?

  • Traps heat energy close to Earth
  • Involves absorption and re-emission of long-wavelength radiation
  • Maintains stable temperatures on Earth
• What are the main sources of greenhouse gases?


  • Carbon dioxide: burning fossil fuels, deforestation
  • Methane: farm animals, waste decomposition
  • Water vapor: natural processes
• What are the consequences of climate change?


  • Increased frequency of extreme weather events
  • Sea level rise due to ice melting and water expansion
  • Loss of biodiversity as species struggle to adapt
• How does global warming affect sea levels?


  • Melting glaciers and polar ice caps add water
  • Warmer ocean temperatures cause water expansion
  • Leads to flooding and submersion of coastal areas
• What is the impact of deforestation on carbon dioxide levels?


  • Reduces photosynthesis
  • Increases carbon dioxide concentration in the atmosphere
  • Contributes to the greenhouse effect