Final answer:
Boiling water causes temporary hardness to be removed due to the precipitation of calcium and magnesium carbonates. Chemicals like sodium carbonate and sodium hexametaphosphate are used to remove hardness by precipitating or sequestering metal ions.
Step-by-step explanation:
The hardness of water is primarily caused by the presence of calcium and magnesium ions. Boiling can remove these ions by precipitating them out of the solution due to the decreased solubility of their respective carbonates at higher temperatures. The chemical reaction representing the boiling process of water is simply the phase change from liquid to gas, written as H₂O (l) → H₂O (g).
To remove hardness of water using chemicals, substances such as ion-exchange resins or substances that precipitate the metal ions, like lime softening agents, are often used. Examples of chemicals are sodium carbonate (Na₂CO₃), which precipitates calcium ions, and sodium hexametaphosphate, which binds to calcium and magnesium ions to prevent them from precipitating and clogging pipes.