Hard & Soft Water
Soft Water = easily forms thick, rich lather with soap (no dissolved substances)
Hard Water = doesn't easily form lather with soap
- contains calcium and magnesium ions
- Calcium & magnesium + soap = SCUM!
Hard water forms...:
- Ca+ Mg ions dissolve in water when pass over rocks containing them
- Rock = limestone (calcium carbonate/insoluable in water)
- Rain falls...CO2 dissolves in it, makes water acidic
- Calcium carbonate reacts with acid - forms calcium hydrogencarbonate
- Soluable in water....Ca ions get into water :)
Hard Water and soap + heating
Calcium + magnesium ions react with water to form SCUM!
- Only once all ions have reacted that lather forms
Hard water leads to SCALE (limescale) forming
- Formed as insoluable soild, when heat a type of water.
- Formed in washing machines, pipes and kettles
- Scale in kettle's (furring up) in heating element, makes kettle inefficient
- Scale = poor conductor of energy - costs more energy to heat water.
Advantages of Hard Water
- Calcium ions develop strong bones and teeth
- Hard water reduces heart disease
Advantages of softening hard water:
- Doesn't waste soap
- No scum or scale is formed when heating
Temporary and permanent hardness
Temporary hard water: water that can have it's hardness removed by boiling
Permanently hard water: water that remains hard after boiling.
Heating temporarily hard water:
- When boil water containing hydrogencarbonate ions they decompose!
- Carbonate ions react with Ca+ or Mg+ ions in hard water - removes them, softens water!
Softening hard water
Washing Soda (sodium carbonate):
- Add sodium carbonate
- Soluable carbonate ions precipitate out calcium and magnesium ions.
- Dissolved metal ions form insoluable carbonates!
Ion Exchange column:
- Removes Ca+ and Mg+ ions
- Column contains resin packed with sodium ions
- Hard water passes through column
- Sodium ions exchanged for calcium and magnesium ions
- Wash resin with salt solution to put sodium ions back in.
As water enters...passes through METAL SCREEN to catch large objects
Settlement tank = sand and soil settled
Aliuminium sulfate and lime added- clump particles together
Passed through filter of fine sand to remove remaining particles
CHLORINE added to kill off bacteria
pH of water checked = water pumped to schools, factories etc...
Further Water Treatment
Water from boreholes clean = filtered through rocks
Water jugs: water enters, passes through filter cartridge
- contains carbon (reduces levels of chlorine, pesticides)
- Ion exchange resin removes calcium, magnesium and lead ions
- Silver = discourages growth of bacteria
Can get 'pure water' by distilling it!
Chlorine....= can react with organic molecules and form toxic products.
- using 'ozone' is an alternative
Fluoride = added to protect teeth from decay
- For flurodiation: been in water for years no harmful effects, reduces cavities in teeth, only added in tiny amount
- Against flurodiation: Flurosis= too much fluoride - can weaken bones cause marks on teeth, ethically wrong to give something with no consent, may affect brain.