What Boiling Water Does
Boiling water involves heating it to its boiling point, effectively inactivating or killing most biological contaminants. This includes common bacteria, viruses, and protozoa that can cause waterborne illnesses.
While boiling is highly effective at disinfecting water from living microorganisms, it does not alter the chemical composition of the water. Non-volatile impurities, such as dissolved minerals like calcium and magnesium, remain. Heavy metals like lead and arsenic, and various chemical contaminants including pesticides, herbicides, and chlorine, are not removed.
Boiled water is primarily a disinfected form of its original source, making biologically unsafe water potable.
What Distillation Achieves
Distillation is a purification process that mimics the natural hydrological cycle. It involves boiling water to create steam, which separates from non-volatile impurities left behind. This steam is collected and cooled, condensing into purified liquid water.
This method is effective because most contaminants, including minerals, salts, heavy metals, and many organic chemicals, have higher boiling points than water or are non-volatile. As water turns into vapor, these substances are left behind, making the condensed water exceptionally pure.
Distillation removes a wide spectrum of contaminants, encompassing biological agents, dissolved solids, and inorganic compounds. It yields nearly pure H2O, with almost all non-water substances physically separated during the phase change.
Comparing Water Purity
The primary difference in purity between boiled and distilled water lies in the contaminants each method removes. Boiled water is primarily disinfected water. It addresses the biological safety of water by eliminating bacteria, viruses, and protozoa through heat.
However, boiling does not remove non-volatile impurities that are dissolved within the water. This includes naturally occurring minerals such as calcium, magnesium, and sodium, as well as pollutants like heavy metals, nitrates, and many synthetic organic chemicals. These substances remain in the water even after it has been boiled.
In contrast, distilled water achieves a significantly higher level of purity because the distillation process physically separates water molecules from virtually all non-volatile contaminants. When water evaporates into steam, it leaves behind dissolved solids, minerals, salts, and most chemicals. The subsequent condensation of this pure steam yields water largely free from both biological and chemical impurities.
Practical Applications and Uses
The distinct purity levels of boiled and distilled water dictate their appropriate applications. Boiled water is suitable for situations where biological contamination is the primary concern. For example, it is often recommended for drinking during emergencies or when the safety of a water source is uncertain, as it makes the water biologically safe for consumption. It is also used for sterilizing items like baby bottles or for basic disinfection purposes where chemical purity is not paramount.
Distilled water, due to its high purity and lack of dissolved minerals, serves a different set of needs. It is commonly used in medical devices such as Continuous Positive Airway Pressure (CPAP) machines and humidifiers to prevent mineral buildup and ensure proper function. Laboratories rely on distilled water for experiments requiring high purity to avoid interference from impurities.
In household settings, distilled water is beneficial for appliances like steam irons, car batteries, and diffusers, where mineral deposits from tap water could cause damage or reduce efficiency over time. While safe to drink, its lack of minerals can give it a flat taste, and it does not contribute to dietary mineral intake. Therefore, distilled water is generally chosen for applications demanding the absence of dissolved solids and chemical purity.