Difference Between Hard Water and Soft Water

Main Difference – Hard Water vs Soft Water

About 71% of earth’s crust is covered with water, but a very little percentage of it is drinkable. Water is an essential component for all living beings in their day to day life. Living beings cannot survive without water. Normal water is composed of H2O molecules, which are called water molecule. Water can be found as hard water and soft water. Hard water is water that has a high mineral content. Soft water is water that has a low mineral content. That is the main difference between hard water and soft water.

Key Areas Covered

1. What is Hard Water
     – Definition, Properties, Temporary Hardness and Permanent Hardness
2. What is Soft Water
     – Definition, Preparation
3. What is the Difference Between Hard Water and Soft Water
     – Comparison of Key Differences

Key Terms: Calcium, Hardness, Hard Water, Magnesium, Minerals, Permanent Hardness, Sodium, Soft Water, Temporary Hardness, Water

Difference Between Hard Water and Soft Water - Comparison Summary

What is Hard Water

Hard water is water that has a high mineral content. In general, hard water consists of a high content of magnesium and calcium minerals. These are dissolved minerals. The hardness of water is the measurement of determining whether water is hard or soft. Hard water is formed when water flows through limestone and chalk, which are made up mainly of magnesium and calcium carbonates.

Minerals in water give it a characteristic taste. The health benefits may also vary depending on the amount of minerals present. Soap is less effective in hard water because it will form a film rather than foam. This is because of the formation of magnesium and calcium slat of the organic acid present in soap.

Main Difference -Hard Water vs Soft Water

Figure 01: Hard Water

The hardness of hard water can be expressed as two types:

Temporary Hardness

Temporary hardness is due to the presence of bicarbonate minerals that can dissolve in water, mainly magnesium and calcium carbonates. These minerals form magnesium and calcium cations (Ca+2, Mg+2) along with carbonate and bicarbonate anions (CO32- and HCO3) when dissolved in water. Temporary hardness can be removed by boiling water or by adding lime.

Permanent Hardness

Permanent hardness is due to sulfates and chlorides of magnesium and calcium. These minerals do not precipitate when heated. Therefore, permanent hardness cannot be removed simply by boiling. It can be removed using water softeners or ion exchange columns.

Hard water can be softened by treating with lime or by passing over an ion exchange resin. Ion exchange resins can replace ions of hard water with sodium cations.  

What is Soft Water

Soft water is water having a less mineral content. Soft water is free from dissolved salts of calcium and magnesium. Soft water mainly contains sodium ions. Soft water is treated to have only sodium cations. Soft water may not be suitable for drinking because of the less mineral content and salty taste. Soap is highly effective on soft water and forms foam when used. 

Difference Between Hard Water and Soft Water

Figure 02: Soft Water

Soft water is produced by treating hard water by passing over an ion exchange resin. The ion exchange resin consists of sodium salts. When hard water passes over the resin, salt ions can replace magnesium and calcium ions in hard water. That is the reason why soft water has a high sodium ion content and taste salty.

Difference Between Hard Water and Soft Water

Definition

Hard Water: Hard water is water that has a high mineral content.

Soft Water: Soft water is water having a less mineral content.

Ions

Hard Water: Hard water contains magnesium and calcium ions.

Soft Water: Soft water contains sodium ions.

Taste

Hard Water: Hard water often has a characteristic taste.

Soft Water: Soft water tastes salty.

Preparation

Hard Water: Hard water is formed when water flows through limestone and chalk.

Soft Water: Soft water is produced by passing hard water over an ion exchange resin.

Effect of Soap

Hard Water: Soap has a less effect on hard water, a film is formed rather than foam.

Soft Water: Soap has a good effect on soft water, foam is formed.

Conclusion

Hard water is water that has a high mineral content. Soft water is water that has a low mineral content. That is the main difference between hard water and soft water. Hard water mainly consists of magnesium and calcium ions. Soft water is composed of sodium ions.

Reference:

1. Helmenstine, Anne Marie. “Chemistry of Hard and Soft Water.” ThoughtCo, Feb. 13, 2017, .
2. “Soft water.” Wikipedia, Wikimedia Foundation, 30 Oct. 2017, .
3. “What is soft water and why it is important.” Water Technology Online, 23 July 2015, .

Image Courtesy:

1. “Hard water and drop” By Hustvedt – Own work via
2. “Blue Drip Beautiful Water Drop Macro Close-up” (CC0) via

About the Author: Madhusha

Madhusha is a BSc (Hons) graduate in the field of Biological Sciences and is currently pursuing for her Masters in Industrial and Environmental Chemistry. Her interest areas for writing and research include Biochemistry and Environmental Chemistry.

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