Water Hardness

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  • Water Hardness
    • Permanently Hard Water
      • Caused by the presence of dissolved calcium sulfate
      • Can be softened by adding washing soda (sodium carbonate)
        • The added carbonate ions react with the calcium and magnesium ions. The calcium and magnesium ions are no longer dissolved in the water
      • Can be softened by running water through 'ion exchange columns'.
        • The columns have sodium (or hydrogen) ions and exchange them for the calcium and magnesium ions in the water
    • Temporarily Hard Water
      • Caused by the presence of hydrogen-carbonate ions
      • Removed by boiling
        • The hydrogen-carbonate ions decompose to form calcium carbonate which is insoluble. This is called limescale
      • Can be softened by adding washing soda (sodium carbonate)
        • The added carbonate ions react with the calcium and magnesium ions. The calcium and magnesium ions are no longer dissolved in the water
      • Can be softened by running water through 'ion exchange columns'.
        • The columns have sodium (or hydrogen) ions and exchange them for the calcium and magnesium ions in the water
    • Soft Water
      • Makes a lather when it reacts with soap
    • Hard Water
      • Makes scum when it reacts with soap unless a soapless detergent is used
        • More soap needed = more money
      • Calcium and magnesium ions make the water 'hard'
        • The calcium and magnesium ions are dissolved from rocks (such as limestone, chalk and gypsum) as magnesium sulfate and calcium sulfate
      • The scum produced is insoluble
      • Forms scale when heated
        • This reduces the efficiency of the appliance, therefore they will need to be regularly replaced- costing money
        • The build up eventually results in the blocking of pipes
        • Acts as a thermal insulator so a kettle (for example)would take longer to boil
      • Calcium ions are good for healthy teeth and bones. People drinking hard water are less at risk of developing heart disease

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