Water

• Substances in water that are harmful

  Microorganisms

  Ions

  Pollutants

  Dissolved gases
• Why do we need sustainable water supply

  Water has risen across the world over the last 100 years
• Reducing water consumption

  Taking showers not baths

  Turn taps off when not used

  Boil amount of water u need
• Reducing abstract water

  Desalination of sea water

  Building dams and reservoirs

  Collecting rainwater
• Distributing water

  Done by underground piping systems that take water directly to peoples houses, businesses, farms
• 3 ways to treat water

  Sedimentation - Water added to a large tank, stops from flowing allowing large insoluble particles to sink to the bottom of the tank

  Filtration - Water flown through beds of sand and gravel which removes small insoluble particles.

  Chlorination - Chlorine gas bubbled through water to kill bacteria and other microorganisms
• For and against on fluoridation

  For:

  Strengthens enamel of teeth which prevents tooth decay and cavities

  Protects teeth from demineralization

  Against:

  Form of mass medication

  Too much fluoride can cause fluorosis
• What is desalination and 2 methods

  Removal of salt from seawater can be done by

  Distillation and reverse osmosis
• How does distillation separate water

  . Seawater is heated casing water to evaporate

  . Water vapor is collected and cooled, causing it to condense back into a liquid, giving distilled water

  . The leftover is salt
• Solubility depends on

  Identity of solute

  Identity of solvent

  Temperature
• Causes of hardness in water

  Contains dissolved magnesium ions and calcium ions. Water dissolves these ions as they run over rocks such as limestone
• How to distinguish between hard and soft waters by their action with soap

  Hard water - Its difficult to form a lather with hard water. Forms scum

  Soft water - Readily forms a lather with soap
• Difference between temporary and permanent

  Temporary forms a lather after boiling and permanent doesn't
• How to remove hardness

  . Sodium carbonate - washing soda which can remove both temporary and permanent

  . Ion exchange - A filter that removes unwanted ions from water, making it softer. It uses resin beads to exchange ions and reduce water hardness
• How to know if its hard water

  More volume of soap solution needed
• How to know if its soft water

  Least amount of soap solution
• Does hard or soft water lather more

  Soft
• how do ions end up in "natural" water supplies

  water dissolves ions from rocks and other micro organisms as it flows within rivers to reach lakes, too much can be dangerous
• what dangerous pollutants dissolve into "natural" water

  pesticides, chemical fertilisers
• how to maintain sustainable water supply

  taking baths instead of showers, treat water effiency
• examples of water abstraction

  desalination of seawater

  building dams
• process of water of seawater distillation

  seawater heated, pure water evaporates

  water vapor is collected and cooled, condenses back into liquid giving distilled water

  leftover salt
• what does hard water and soap form

  forms scum
• what does soft water and soap form

  readily forms a lather
• temporary hardness in water

  caused by dissolved calcium hydrogencarbonate

  can be removed by boiling
• permanent hardness in water

  caused by dissolved calcium sulphate

  cannot be removed by boiling
• process to soften water

  distillation

  adding sodium carbonate

  using ion exchange collumn
• advantages to use distillation to soften water

  removes both temporary and permanent hardness
• disadvantages of using distillation

  high energy - high cost
• advantages to use sodium carbonate to soften water

  cheap and easy

  removes both temporary and permanent hardness
• disadvantages of using sodium carbonate to soften water

  calcium carbonate (limescale) builds up and blocks pipe
• advantages of using ion exchange to soften water


  removes both temporary and permanent hardness
• disadvantages of using ion exchange


  expensive

  becomes saturated and less efficient
• how does distillation soften water

  hard water is heated so water evaporates. Th water then condenses and is collected leaving behind the ions making it hard.
• how does adding sodium carbonate make water soft

  carbonate ions react with calcium ions in water to form solid calcium carbonate
• advantages of hard water

  prefer taste

  strengthens bones and teeth
• disadvantages of hard water

  scum forms

  difficult to form a lather