Water hardness measures the concentration of specific dissolved minerals within the water.
Understanding Water Hardness
Water hardness is a key indicator of water quality that describes the amount of dissolved minerals present. It's not related to the physical sensation of water but rather its chemical composition.
The Measurement Explained
According to the provided information, water hardness is fundamentally "the measurement of the number of ions that have lost two electrons (divalent cations) dissolved in the tested water".
This means that hardness quantifies the presence of specific positively charged particles that carry a +2 electrical charge. As the reference states, "The more divalent cations dissolved in the water, the "harder" the water."
What are Divalent Cations?
Divalent cations are atoms that have lost two electrons, resulting in a +2 charge. The most common divalent cations contributing to water hardness are:
- Calcium (Ca²⁺)
- Magnesium (Mg²⁺)
Other less common divalent cations found in water include strontium (Sr²⁺) and barium (Ba²⁺). The combined concentration of these ions determines the water's hardness level.
Connection to Total Dissolved Solids (TDS)
The reference highlights that water hardness "is, therefore, related to total dissolved solids." Total dissolved solids (TDS) is a measure of the total amount of all dissolved substances in water, including minerals, salts, and organic matter. Since divalent cations are dissolved minerals, they contribute to the overall TDS measurement. However, hardness specifically focuses on the concentration of these particular +2 charged ions.
Practical Implications of Water Hardness
The level of water hardness has practical effects in daily life:
- Soap and Detergent Use: Hard water reacts with soap, reducing its lathering ability and forming insoluble soap scum. More soap or detergent is needed to achieve the same cleaning results.
- Scaling: When hard water is heated or evaporates, the dissolved minerals (primarily calcium and magnesium) can precipitate out, forming scale deposits on surfaces, pipes, and appliances like water heaters, dishwashers, and kettles.
- Appliance Lifespan: Scale build-up can reduce the efficiency and shorten the lifespan of water-using appliances.
- Appearance: Hard water can leave spots and films on dishes, glasses, and fixtures.
Measuring water hardness helps in understanding these potential issues and deciding whether water softening or treatment is necessary.
