Answer "Task 4. Short answer". What is "water hardness"? Name its method of elimination.

Water Hardness:

Water hardness refers to the concentration of dissolved minerals, primarily calcium (Ca²⁺) and magnesium (Mg²⁺) ions, in water.

Methods of Elimination:

• Ion Exchange: This is the most common method. Water passes through a resin that exchanges calcium and magnesium ions for sodium (Na⁺) or potassium (K⁺) ions.
• Chemical Precipitation: Chemicals like lime (calcium hydroxide) or soda ash (sodium carbonate) are added to precipitate out the hardness minerals.
• Reverse Osmosis: This advanced filtration method removes most dissolved salts and minerals.
• Boiling (for temporary hardness): Heating water can cause dissolved bicarbonates of calcium and magnesium to precipitate out as carbonates, reducing temporary hardness.

Note: The image prompts for a method of elimination, and ion exchange is a primary one.