Why cold weather makes your water pipes burst

11/27/2017 (Permalink)

Why Cold Weather Makes Your Water Pipes Burst

The cold weather is quickly approaching

Why Do Pipes Burst the Way They Do?

Why do water pipes burst, and why do they always fail the same way? These are two interesting questions.

Water pipes burst because the water inside them expands is it gets close to freezing, and this causes an increase in pressure inside the pipe. When the pressure gets too high for the pipe to contain, it ruptures.

We grew up with water all around us and so this expansion phenomenon seems natural, but interestingly, it is a chemical anomaly. Most liquids do not expand just before transitioning to solid. You should be thankful for this; it is one of the reasons that life exists.

When a liquid cools the molecules slow down (temperature really is just a measure of the average kinetic energy of the molecules). This slowing down allows the molecules to get closer together and increases the density of the liquid. This happens with water too, and when water is cooled down, it gets denser and denser, down to 3.98°C then, something interesting occurs; it starts to expand again.

Because of the shape of a water molecule, it is slightly polarized. The electrons buzzing around it are more likely to be on one side of the molecule than the other (called a dipole), and this asymmetry creates a slight potential. Water molecules are attracted to each others' opposite sides. These potentials create weak bonds that are called Hydrogen Bonds. Hydrogen bonds, whilst not as strong as covalent bonds or ionic bonds, are stronger that van der Vaals forces.

Water is a liquid at everyday temperatures and pressures (another one of the reasons life exists). Other chemical compounds similar to H₂O, but without the benefit of Hydrogen bonds, are all gases in typical Earth temperature ranges.

The Hydrogen-bonds in water are also the reason why water has such a high specific heat capacity (the amount of energy required to raise the temperature of water one degree); this helps dampen our weather and stops the Earth changing in temperature too rapidly. It also means that water is great for carrying energy around (like in power stations and hydronic central heating systems). It's also why it takes a lot of energy to boil a kettle to make a nice cup of tea!

As water cools, like other liquids, the molecules slow down and get denser. A competing force, however, is the desire for the water molecules to align with other water molecules based on their Hydrogen bonds, and this causes expansion. Below the temperature of 3.98°C down to 0°C, this alignment expansion process wins out against the desire of slower molecules to get closer, and density decreases.

Whilst not completely understood, it is this expansion that causes beautiful snowflakes to form with their characteristic six points.

This decrease in density continues until the water finally freezes to form ice. Water expands to form ice which has a volume up to 9% greater than the water it came from. It is this reason that icebergs float (being less dense than the water they displace).

Again, it seems natural to us that ice floats, because we grew up this all effect all around us, but this is atypical.

Most other liquids, when freezing, do not form a solid 'crust' on top. As they cool, the solid formed, being denser, drops to the bottom of the cooling liquid and the solid grows up from the bottom!

This irregular behavior of water is yet another reason that life exists. When water freezes, it floats to the top, forming a skin which insulates the water below. When a river or lake freezes on top, life continues below in the liquid left underneath.

In other words, insulate your pipes this winter!

This post was originally published on Data Genetics, a site created by Nick Berry was educated as a rocket scientist and aircraft designer, graduating with a Masters Degree in Aeronautical and Astronautical Engineering, and currenty works as a Data Scientist at Facebook. You can follow DataGenetics on Twitter here or on Facebook page here.

Article source: https://gizmodo.com/why-cold-weather-makes-your-water-pipes-burst-1480690222