Leo & Leah

We consume aqueous solutions every day. A solution is a substance in which two or more materials are uniformly mixed without separation. While most solutions are liquid, they can also involve solids or gases. A solution is composed of a solvent and a solute. When two or more liquids are mixed, the one present in greater quantity is called the solvent, and the one in lesser quantity is called the solute. When different states of matter (e.g., solid + liquid, gas + liquid) mix to become a liquid, the liquid is the solvent, and the other state of matter becomes the solute. An aqueous solution is a solution where water is the solvent. In this case, the solute can be any substance that dissolves in water. Most beverages like juice, tea, soda, ion drinks, beer, and whiskey are aqueous solutions. In other words, various components that dissolve in water make up the solute in water.

Bottled spring water, commonly called “dirnking water,” contains dissolved mineral components. These solute components present in water can be removed through processes like purification or distillation. Typical household water purifiers remove 99% of solutes from tap water. Water that has been boiled and then condensed is called distilled water, and further filtering of distilled water removes solute components, resulting in deionized water (DI water). There is a misconception that drinking pure water will lead to stomachaches and diarrhea, but this is incorrect information. When water is poured into any container, even DI water, a small amount of solute from the environment is absorbed. From the moment it enters our mouths and is absorbed in the digestive system, various solute components in high concentrations dissolve and mix. Thus, it is no longer pure water when it reaches the stomach.

Natural spring water tastes different depending on its source or brand. The type and quantity of dissolved minerals and the water’s acidity are major factors influencing water taste. The mineral composition and acidity are somewhat related. Drinking water can be categorized as hard water (high calcium and magnesium ion content, > 121 mg/L) or soft water (low calcium and magnesium content, < 60 mg/L). Hard water, with high levels of calcium and magnesium ions, tends to have a chalky, bitter taste. Soft water, with low levels of calcium and magnesium but higher levels of sodium (Na⁺) and potassium (K⁺) ions, tastes relatively milder. The most favorable taste is generally achieved when the total mineral content in drinking water is around 100 mg/L. Therefore, for taste enhancement, bottled water artificially adds minerals. Hard water, with high levels of alkaline earth metal ions (Group 2 elements on the periodic table, which form 2⁺ cations when dissolved in water), typically originates in areas with a high calcium component in their groundwater. The water from areas rich in limestone can carry calcium and magnesium ions into the water. Hard water has an alkaline pH level above 8.5. Pure water has a neutral pH of 7, having no discernible taste, but when the pH drops to lower level than 7, it can result in a sour or metallic taste. Alkaline (> pH 8.5) water tends to have a slippery texture and a bitter taste.

References

1. Lucy and Harris, (2017) Quantitative Chemical Analysis. 9^th Ed., W.H. Freeman and Co.

2. Oxtoby et al. (2002) Principles of modern chemistry. Thomson/Brooks/Cole

3. World Health Organization. Sustainable Development and Healthy Environments Cluster. (‎2005)‎. Nutrients in drinking water. World Health Organization.

4. Sengupta, Int. J. Prev. Med., 2013, 8, 866