Exploring the Properties of Water at -10 Degrees Celsius

Introduction

The properties of water at different temperatures are crucial in numerous scientific and industrial applications. One such temperature is -10 degrees Celsius (-10°C), which presents unique physical states and behaviors. This article explores the confusion surrounding the freezing point of water at this temperature, as well as the physical states of water based on pressure and purity.

Understanding the Celsius Scale

When discussing the freezing point of water at -10°C, it is essential to understand that the definition of the Celsius scale itself is based on the freezing and boiling points of water at standard atmospheric pressure. According to the original definition by Anders Celsius, 0°C was set as the freezing point of water, and 100°C as the boiling point. This implies that -10°C is 10°C below the freezing point of water and not its freezing point.

Temperature Conversion and Scaling

The ratio between Fahrenheit and Celsius is approximately 1.98, which means that a rise of 10°C (or 100 Fahrenheit degrees) is roughly equivalent to 19.8 Fahrenheit degrees. Conversely, a drop of 10°C (or 100 Kelvin degrees) translates to a drop of 100 Kelvin degrees. This is important for understanding how temperature scales relate to each other.

Water's Freezing Point and Reality

The statement that water can have a freezing point of -10°C is incorrect. The freezing point of water at standard atmospheric pressure is defined as 0°C. Changing this would fundamentally alter the definition of the Celsius scale and the way we measure temperatures. Moreover, the freezing point of water is related to the physical properties of hydrogen bonds, which are inherently set at 0°C under standard conditions.

Physical States of Water at -10°C

The physical state of water at -10°C can vary depending on pressure and purity. Under standard atmospheric pressure, water remains a liquid at -10°C due to the lack of sufficient cooling. However, under different pressures, water can exhibit different states.

Solid State: Under extremely low-pressure conditions, water can remain liquid at -10°C. However, at standard atmospheric pressure, water freezes at 0°C, making -10°C well above the freezing point. Liquid State: At -10°C and standard atmospheric pressure, water is in a liquid state. However, at higher pressures (e.g., in the stratosphere), the freezing point can be lower, leading to the formation of liquid water even at temperatures below 0°C. Vapor State: At -10°C and sublimation conditions, water can exist as a vapor. Sublimation, a process where a solid transitions directly into a gas, can occur under very low-pressure conditions at -10°C. The sublimation pressure at -10°C is approximately 0.002599 bar, indicating a high vacuum environment.

Metastable States and Non-Equilibrium Conditions

Water can exhibit metastable states in non-equilibrium conditions, such as in the stratosphere. Here, water can solidify at temperatures well below its normal freezing point due to its purity and the absence of nucleation sites. These metastable states are crucial in understanding phenomena like clouds and condensation trails from jet aircraft.

In the stratosphere (approximately -20°C to -50°C), water in the form of vapor can exist in a non-equilibrium state, where it can condense into liquid droplets or solid ice crystals. These conditions are common in high-altitude clouds known as polar stratospheric clouds. In these clouds, the water can remain in a metastable, liquid or solid state, depending on its purity and the turbulent mixing within the cloud.

Conclusion

Understanding the physical properties of water at -10°C is crucial for various scientific and industrial applications. The freezing point of water is set at 0°C under standard atmospheric pressure, and the Celsius scale defines temperatures based on this point. The physical states of water, including its metastable states, can vary significantly depending on pressure and purity. This information is valuable for meteorologists, atmospheric scientists, and engineers working in various fields.