What is hard water?

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ndnordic's profile pic

ndnordic | High School Teacher | (Level 2) Associate Educator

Posted on

The term hard water means that the water contains relatively high amounts of calcium and/or magnesium ions dissolved in the water. Hard water occurs naturally in many parts of the U.S., especially in areas where there are layers of limestone underground.

Hard water is perfectly safe to drink, although very high levels may give it a taste that some people may not like.

Because of the presence of the calcium and magnesium ions, when soap is added a chemical reaction occurs, resulting in the precipitation of the soap-calcium compound.  If you lived in an area that had hard water you may see a ring of soap scum and dirt on the sides of the bathtub.

One test for hard water is to add a few drops of soap to a container of water and shake the container vigorously. If no foam appears the water is hard.

If you boil hard water, the minerals are left behind when the water evaporates, forming a deposit on the bottom of the pot.

justaguide's profile pic

justaguide | College Teacher | (Level 2) Distinguished Educator

Posted on

Hard water is water with a high concentration of calcium and magnesium ions. The presence of these ions alters the taste of water and makes it unpalatable. When hard water is heated the dissolved chemicals result in the formation of scales. This does not allow the use of hard water in boilers, heating systems and other similar applications without damaging them.

The ions in hard water also make it very difficult to use soap, as most soaps cannot generate a foam and clean effectively in the presence of hard water.

Soft water is created by either removing all chemical ions from hard water, or by replacing the ions of calcium and magnesium with those of sodium. The softening of water makes it possible to use it again in a normal way for all purposes.

crims's profile pic

crims | Student, Grade 9 | (Level 1) eNoter

Posted on

Hard water is water that has high mineral content (in contrast with soft water). Hard water has high concentrations ofCa2+ and Mg2+ ions. Hard water is generally not harmful to one's health but can pose serious problems in industrial settings, where water hardness is monitored to avoid costly breakdowns in boilers, cooling towers, and other equipment that handle water. In domestic settings, the hardness of water is often indicated by the non-formation of froth when soap or toothpaste are agitated in the water sample. Hardness in water is defined as concentration of multivalent cations. Multivalent cations are cations with a charge greater than 1+, mainly dications. These dications include Ca2+ and Mg2+. These ions enters a water supply by leaching from minerals. Common calcium-containing minerals are limestone, a form of calcium carbonate (CaCO3), and chalk (calcium sulphate, (CaSO4). A common magnesium mineral is dolomite (CaMg(CO3)2), which also contains calcium. Rainwater and distilled water are soft, because they contain few ions.

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