Water

• • Water is a compound with the formula H2O - 2 hydrogen atoms and 1 oxygen atom.
• Water supply originates as rainwater - water falls as rain, CO2 and O2 dissolve in water - dissolved CO2 lowers pH of rainwater, making it slightly acidic and is needed by plants in bodies of water (rivers, streams) for carrying out photosynthesis - dissolved O2 allows aquatic organisms to respire.
• After falling as rain, water then runs through soil and rocks in ground and dissolves metal ions from minerals in the rocks - most common metal ions found in natural water = sodium (Na^+), potassium (K^+), calcium (Ca^2+), magnesium (Mg^2+).
• Natural water can also contain pollutants which can cause harm to humans if consumed:

  • Natural pollutants (microorganisms) - bacteria, viruses, animal faeces.
  • Man-made pollutants- fertiliser, pesticides, household and industrial waste.
• • Pure water boils at 100°C and freezes at 0°C, but daily water isn’t pure so won’t boil and freeze at this accurate temperature.
• Uses of water:

  • Coolant in factories.
  • For hygiene purposes (washing and keeping clean).
  • Growing plants and food.
  • As a solvent (dissolve minerals and gases).
  • Drinking water.