Using the Earth’s resources and obtaining potable water

10.1.1 Using the Earth’s resources and sustainable development

  • Human use of Earth’s resources – provide warmth, shelter, food & transport
  • Natural resources, supplemented by agriculture – provide food, timber, clothing & fuels
  • Finite resources, ocean, atmosphere – provide energy & materials

Role of Chemistry

  • Improve agricultural & industrial processes – provide new products & sustainable development
  • To meet needs of current generations without compromising ability of future generations to meet their own needs

10.1.2 Potable water

Types of water

Type Description Dissolved substances Microbes
Pure water Only contains water molecules No No
Potable water Safe to drink Low Extremely low
Fresh water Collected in ground, lakes, rivers Low Low
Ground water Fresh water found in underground streams & aquifers Low Yes
Sea water In seas High Yes
Waste water Used water from homes, industry & agriculture High Yes
Hard water Contains Mg2+ and Ca2+ Low Yes

What is in water filters that removes hardness from water? (1)

  • Ion exchange resin

State health benefits of drinking hard water (1)

  • Hard water contains mineral content that maintains bones/teeth & reduces heart disease

Describe how water in the United Kingdom is treated. Explain how this makes it safe to drink. (4)

What are the two main steps used to treat water from reservoirs? Give one reason for each step. (4)

  • Choosing an appropriate source of fresh water
    •                In UK – rain coz low levels of dissolved substances, collects in the ground, lakes & rivers
    • Filter to remove solids
    • Sterilisation – add chlorine / ozone / UV light to kill microbes

Why do some water companies add fluoride to drinking water? (1)

  • Improve dental health

Explain why it’s more difficult to produce drinking water from waste water than from water in lakes (3)

  • Water needs more processes coz it contains more organic matters & microbes

How could the water be tested to show it’s pure? (2)

  • Determine its boiling point, which should be 100°C
  • Desalination

    If fresh water is limited → desalination of sea water

    • By distillation
    • By processes that use membranes eg reverse osmosis

    Name the substance removed from seawater by desalination (1)

    • Sodium chloride

      Why is desalination expensive? (1)

    • Requires a large amount of energy

     Suggest why water filters used in home contain particles of silver (1)

    • Prevent growth of microbes

Desalination of seawater can be carried out by processes that use membranes such as reverse osmosis. Describe one other way to desalinate sea water in a school laboratory. (4)

  • Distillation
  • Heat a flask (containing sea water) until it boils
  • Use of a condenser / delivery tube
  • Collect (pure water) in a boiling tube / beaker / flask

10.1.3 Waste water treatment

  • Sewage & agricultural wastewater → remove organic matter & harmful microbes
  • Industrial wastewater → remove organic matter & harmful chemicals

Types of sewage treatment

  • Screening & grit removal
  • Sedimentation → produce sewage sludge & effluent
  • Anaerobic digestion of sewage sludge
  • Aerobic biological treatment of effluent

10.1.4 Alternative methods of extracting metals (HT only)

Methods of extracting copper from low-grade ores

  1. Phytomining
  • Use plants to absorb metal compounds
  • Harvest plants, then burn them to produce ash that contain metal compounds
  1. Bioleaching
  • Use bacteria to produce leachate solutions that contain metal compounds

Suggest two methods to obtain copper from solutions of copper compounds? (2)

  • By displacement using scarp iron
  • By electrolysis

Why are phytominig and bioleaching used to extract copper? (1)

  • Avoid digging, moving & disposing large amounts of rock

Explain why the gaseous product should not be released into the atmosphere (2)

  • Sulfur dioxide is an environmental pollutant causing acid rain

Describe how copper compounds are obtained by phytomining (2)

  • Grow plants on land containing copper ores, then burn the plants Ash (from burning) contains copper compounds

Extraction from bauxite

  • High temperature needed to melt bauxite/ore
  • Large amount of electricity used
  • Higher energy costs
  • Uses more natural resources
  • Bauxite must be quarried so more damage to the environment
  • Purity of aluminium produced is higher


  • Reduces waste going to landfill
  • Uses less natural resources
  • Lower energy costs
  • Aluminium must be separated from other materials
  • Purity of aluminium is lower.