Frozen Pipes and Mercury Thermometers: The Role of Temperature and Pressure

In this article, we will explore why frozen water pipes can burst and what happens when a temperature drops below the freezing point of mercury in a thermometer. These topics are crucial for understanding basic physical phenomena and their applications in daily life.

Why Do Frozen Water Pipes Burst?

Frozen water pipes are a common occurrence during cold weather, and their potential to burst can cause significant property damage. The bursting of water pipes occurs due to the expansion of water as it freezes. Here is a detailed breakdown of the process:

Water Expansion

When water freezes, it expands by approximately 9% in volume. This expansion is due to the formation of ice crystals, which take up more space than liquid water molecules.

Pressure Build-Up

If the frozen water forms in a confined space, such as a pipe or a valve, the pressure can build up significantly. This is because the expanding ice takes up the same amount of space as the liquid water, but in a solid state. As more water freezes, the pressure inside the pipe increases. If the pressure becomes too high for the pipe material to contain, it can result in a burst, leading to water leaks and potential structural damage.

Location of Freeze

Pipes that are poorly insulated or located in unheated areas such as basements, attics, or crawl spaces are more susceptible to freezing. The ice can form at any point in the pipe, leading to pressure build-up behind the blockage. Temperature fluctuations can cause the ice to melt and then refreeze, further increasing the risk of a burst.

The Curious Case of Mercury Thermometers

Mercury thermometers are designed to operate within a specific temperature range. They would also break if subjected to temperatures below the freezing point of mercury, which is -38.83°C (-37.89°F). Here is an explanation of why:

Freezing Point of Mercury

Merccury remains in a liquid state at much lower temperatures than water. However, when the temperature drops to below -38.83°C, mercury solidifies. This solidification process involves expansion, similar to what happens with water as it freezes.

Expansion Upon Freezing

When mercury solidifies, it expands. If the temperature drops below the freezing point of mercury, the mercury will solidify and expand. If the glass tube of the thermometer cannot accommodate this expansion, the glass can break. This is why mercury thermometers are typically used in situations where the temperature won’t drop below their freezing point.

Conclusion

In conclusion, frozen water pipes burst due to the expansion of freezing water and the resulting pressure build-up within confined spaces. Similarly, a mercury thermometer would break if subjected to temperatures below the freezing point of mercury due to the expansion of the solidified mercury. Understanding these phenomena is crucial for maintaining safe and functional facilities during cold weather.