The Freezing Behavior of Water and Its Contaminants

The freezing behavior of water is an intriguing topic, often misunderstood due to the prevalence of myths and misconceptions. This article delves into the complexities of why water freezes and how various impurities can affect this process. We'll also explore related phenomena such as the effects of hot water on snow and the freezing points of saliva and breath, debunking common beliefs along the way.

Purity and Freezing Rate: A Misconception Busted

A popular myth suggests that distilled water (which is pure H2O) freezes faster than tap water due to the lack of impurities. However, this is a misconception. In fact, based on the principle of ice nucleation, water containing impurities can freeze faster due to the presence of these substances.

When water is pure, it can form an ice lattice more freely. However, impurities like salt or minerals can interfere with the crystal lattice structure of ice, causing nucleation to occur at lower temperatures. This phenomenon, known as the Mpemba effect, has been the subject of much scientific debate. Pure H2O may form ice more slowly due to its higher surface tension and lower nucleation rate.

Hot Water and Its Impact on Snow

Another intriguing phenomenon is the effect of pouring boiling water on snow. This simple act can have significant consequences, often leading to the cracking of windshield glass. The rapid change in temperature when hot water is poured onto a frozen surface generates thermal stress, which can cause the glass to chip or crack.

When hot water is poured over snow, the glass expands due to the heat, followed by a sudden contraction as it cools. This sudden thermal shock can cause microdefects in the glass to expand into larger cracks, potentially resulting in a complete failure of the windshield.

Freezing Points and Environmental Factors

Ground Temperature and Freezing

The temperature at which water freezes depends on the medium it has to cool through. When it comes to the ground, the temperature must drop to 0°C (32°F) for water to freeze. However, it's important to note that while the air temperature can indicate whether water will freeze, the ground temperature can vary due to its thermal inertia and insulation properties.

Urination and Freezing

Regarding the question of whether urine can freeze mid-air, there's no need to worry. At ground level, urine is exposed to temperatures that are too mild for it to freeze even in extremely cold regions. But if someone were to urinate in extremely cold air, say from a high-altitude fall, then it's theoretically possible for the urine to freeze mid-air.

Urine is a complex mixture of water and various solutes, including urea, creatinine, and electrolytes. These solutes can lower the freezing point of the liquid, but they don't usually create a freezing point low enough for urine to freeze in the air under normal conditions.

Saliva and Its Freezing Characteristics

Saliva, a crucial component for many biological and medical processes, can be stored at low temperatures without losing its vital characteristics. Studies have shown that saliva can be frozen and stored at -20°C or -80°C for up to two months, with minimal loss in properties.

A study comparing the total antioxidant capacity (TAC) of saliva stored at different temperatures found a similar decrease in TAC regardless of the storage temperature. This suggests that saliva can be effectively stored for up to 30 days at -20°C, making it a viable option for long-term storage in clinical settings.

Storage of Saliva Samples

For long-term storage, saliva can be stored in swabs for up to six months at -20°C or -80°C. For extended periods, it is recommended to express the saliva from the swabs and transfer it to cryovials to maintain its viability and integrity.

Conclusion

The freezing behavior of water and its contaminants is a fascinating area of study with practical implications in various fields. From debunking common misconceptions about water's freezing behavior to understanding the impact of hot water on snow and the storage of saliva, there is much to learn about how temperature and purity affect these phenomena.

By understanding these principles, we can better predict and manage these events, ensuring safety and efficiency in various applications.