Hard and Soft Water

Soft Water

• Some places in Britain only have Soft Water
• Soft Water lathers well if mixed with soap because it doesn't contain certain chemicals that hard water contains.
• Soft Water forms if the drainage basin of the water used in the area is hard, impermeable and calcium-poor.

Hard Water

• Some places in the UK only have Hard Water
• Hard Water contains Magnesium ions and Calcium ions
• It doesn't lather well when mixed with soap
• Hard water often forms if the drainage basin of the area where the water is used contains calcium-heavy rocks or limestone.

Temporary Hardness

• Water becomes temporarily hard when it comes into contact with Calcium Hydrogencarbonate or Ca(HCO3)2
• Calcium Hydrogencarbonate Thermally Decomposes to make Calcium Carbonate, Water and Carbon Dioxide.
• Ca(HCO3)2 ---> CaCO3 + H2O + CO2
• Calcium Carbonate becomes Limescale, which often lines pipes and kettles

Permanent Hardness

• Water Becomes Permanently hard when it comes into contact with Calcium Sulphate
• CaSO4
• Calcium Sulphate does not decompose so the water remains hard.

Softening Water

• Using Sodium Carbonate
• Hard water becomes soft when Na2CO3 is added.
• Sodium Carbonate is soluble in water and makes the Carbonate ions react with Calcium, forming a CaCO3 precipitate.
• Using Ion-Exchange Resins
• The resin is often a small tube filled with tiny balls of polymers
• The resin exchanges Sodium ions on the resin for Calcium ions in the water.