* Temporary Hardness: This is caused by the presence of dissolved calcium and magnesium bicarbonates (Ca(HCO₃)₂ and Mg(HCO₃)₂). It is called "temporary" because it can be easily removed by boiling the water, causing the bicarbonates to decompose into carbonates (CaCO₃ and MgCO₃), which precipitate out as scale.
* Permanent Hardness: This is caused by the presence of dissolved calcium and magnesium sulfates and chlorides (CaSO₄, MgSO₄, CaCl₂, MgCl₂). It is called "permanent" because it is not easily removed by boiling.
Let me know if you would like more information about either type of hardness!
