Hard and soft water

Hard and soft water

1. Scum

   • calcium ions react with soap to form scum
     • insoluble precipitate
     • more soap needed and used
       • more money used
     • soapless detergent
       • doesnt contain sodium stearate and wont react with calcium ions to form scum

2. scale

   • insoluble solid
   • reduces efficiency

3. lather

4. hard- contains dissolved compunds----magnesium and calcium

5. Benefits of hard water

   • bone development
   • teeth development
   • reduce heart disease
   • reduces risk of lead poisioning ans some intestinal cancers
   • increases overall lifespan

6. hard water can be either

   • temporary
     • can be softened by heating/boiling
   • permanent
     • remains hard even when heated/boiled

7. Softening Hard water

   • add washing soda - sodium carbonate
     • calcium+carbonate=calcium carbonate+sodium
   • ion exchange column contain resins
     • sodium or hydrogen ions in the resin
       • calcium and magnesium exchanged with the sodium/hydrogen in the resin
   • temp hard water contain hydrogencarbonate ions(HCO3-)
   • hydrogencarbonate ions when heated decompose into carbonate ions which react with magnesium or calcium ions found in the hard which leaves us with either magnesium carbonate or calcium carbonate
   • limescale - as hard warer evaporates/heated some carbon dioxide is lost with the water and calcium carbonate reforms....can be easily removed by dissolving in a weak acid
   • drinkable water
     • filter beds remove smaller and smaller solids...if from river it would be passes through sieve to remove large objects
     • activated carbon---- charcoal that is broken up inro granules to increase surface area an then treated to give pieces a slight positive charge. some contaminents stick to filter which should be replaced regularly
     • ceramic filters with microscopic particles of silver - kill any microorganisms that might otherwise grow in the filter
     • Purify or enhance
       • distillation--evaporate sea water and allow re condensation eleswhere leaving salt and impurities behind
         • expensive
       • screens made of metal---remove debris like leaves or twigs that are in the reservoir
         • settlement tank - sand,soil settles out
           • aluminium sulfate- makes particles of dirt clump together and settle ( aka coagulation or flocculation)
             • filter bed - fine sand filters remaining particles (insoluble solid)
               • add chlorine - to kill bacteria / (added in some area) fluorine - hardens teeth
                 • fluorine - reduce tooth decay and added only in tiny amounts but possible links with learning difficulties and unethical (no choice if we can have fluroine or not)
       • carbon - remove/reduce chlorine levels an possibly other chemicals eg trace of pesticide
         • ion exchange resin removes calcium magnesium mainly
           • silver discourages bacterial growth on resin