C14 - The Earth's resources

• What do we rely on the Earth's natural resources for?

  To make homes, provide food, and energy
• How have chemists contributed to the use of natural resources?

  They developed synthetic alternatives to natural products
• How can natural resources be classified?

  • Finite resources
  • Renewable resources
• What are finite resources?

  Resources used faster than they can be replaced
• What are renewable resources?

  Resources that can be replaced at the same rate
• Why do estimates of finite resources vary significantly?

  Due to uncertainties in future use and discovery
• What is the significance of recycling in resource predictions?

  It may significantly affect resource availability estimates
• What is desalination?

  Converting salty water into potable water
• What are the two methods of desalination mentioned?

  Distillation and reverse osmosis
• How does reverse osmosis work?

  It uses membranes to separate water from salts
• What is the main drawback of distillation for desalination?

  It requires large amounts of energy
• What is the first step in sewage treatment?

  Screening to remove large solid objects
• What happens during primary treatment of sewage?

  Solid sediments settle out to form sludge
• How does secondary treatment differ from primary treatment?

  Secondary treatment uses microorganisms to break down matter
• What is the purpose of aeration in sewage treatment?

  To allow bacteria to break down organic matter
• What can be done to treated sewage before discharge into rivers?

  Filter through sand and sterilize with UV light
• What can sewage sludge be used for?

  As fertilizer or renewable energy source
• What are the benefits of anaerobic digestion of sewage sludge?

  It produces biogas for energy use
• What is the main product of anaerobic digestion?

  Biogas, including methane
• How can copper be extracted from copper-rich ores?

  By smelting and purifying the copper
• What is the role of scrap iron in copper extraction?

  It displaces copper from copper sulfate solution
• What is bioleaching?

  Using bacteria to extract copper from ores
• What is phytomining?

  Growing plants to absorb copper ions from soil
• What are the main steps in sewage treatment?

  1. Screening to remove large solids
  2. Primary treatment for sedimentation
  3. Secondary treatment with aeration
  4. Final treatment and sterilization
• What are the advantages and disadvantages of using renewable resources?

  Advantages:

  • Sustainable and replenishable
  • Reduces reliance on finite resources

  
  

  Disadvantages:

  • May require significant land use
  • Initial setup costs can be high
• What occurs at the cathode during electrolysis of copper sulfate solution?

  Reduction of copper ions to copper metal
• What occurs at the anode during electrolysis of copper sulfate solution?

  Oxidation of copper metal to copper ions
• How can copper be extracted from copper sulfate solution in industry?

  By adding scrap iron to displace copper
• What is the ionic equation for the displacement of copper by iron?

  Fe(s) + Cu²⁺ (aq) → Fe²⁺ (aq) + Cu(s)
• Why are scientists developing ways to extract copper from low-grade ores?

  Traditional methods are uneconomical for low-grade ores
• What are the methods used to extract copper from low-grade ores?

  • Bioleaching: Bacteria feed on low-grade ores
  • Phytomining: Plants absorb copper ions from soil
• How does phytomining extract copper from low-grade ores?

  Plants absorb copper, then are burned for ash
• What happens to the copper ions in the ash after burning plants in phytomining?

  They are leached with sulfuric acid to form leachate
• What is the role of scrap iron in copper extraction?

  It displaces copper from its solution
• What percentage of copper comes from bioleaching?

  About 20%
• Why is bioleaching considered a slow process?

  It can take years to extract significant copper
• What is Life Cycle Assessment (LCA) used for?

  To assess environmental impact of products
• What stages are included in a Life Cycle Assessment (LCA)?

  • Raw material extraction
  • Manufacture
  • Use/Reuse/Maintenance
  • Recycle/Waste management
• What does an LCA evaluate?

  Potential environmental impacts from inputs and outputs
• Why is assigning numerical values in an LCA subjective?

  It involves judgments by analysts or panels