Water cycle

• Water Cycle


  The natural phenomenon where water is constantly recycled
• Water Cycle


  1. Evaporation from land and water

  2. Water vapour carried by warm air

  3. Condensation to form clouds

  4. Precipitation falls to land

  5. Water flows into the sea
• If not for the water cycle constantly recycling water, we'd quickly run out of it
• Drought


  When there isn't enough precipitation
• Droughts


  • Can cause big problems because we rely on precipitation for freshwater
  • Desalination can be used to produce potable water from salt water
• Desalination


  Removing salts (mineral ions) from salt water
• Thermal desalination


  1. Salt water boiled in vessel

  2. Water vapour condenses

  3. Salts left behind
• Reverse osmosis desalination


  1. Salt water fed into vessel with semi-permeable membrane

  2. Pressure causes water to move from high to low salt concentration

  3. Salts left behind
• Higher salt concentration in solution


  Lower water concentration
• Reverse osmosis


  Net movement of water molecules in opposite direction to normal osmosis
• Explain how water from the sea can eventually fall as rain
• Material Cycles