Why is salt used to melt snow and ice on roads?


Snow plows and streams
A total of 1,483 snow plows and 252,466 tonnes of flux (mostly salt) are part of the government’s plan for this year’s winter campaign on Spain’s roads.
Montse Hidalgo Montse Hidalgo Weathered Spain 4 minutes

In this article we will try to understand why salt is so important in winter, against the formation of snow and ice along our roads.

Salt has the property of lowering the freezing point of water. When in contact with water, the salt molecules split into ions, which electrostatically bind to the water molecules. But have you ever wondered why salt is added as “kryptonite” from snow and ice?

The combination of salt and water has a purely chemical explanation

The common belief is that salt melts snow as such, but this is not entirely true: mixing water and salt does not increase the temperature. It’s pure chemistry, so we’ll start by analyzing its components.

Sodium and chlorine atoms of salt

First we have sodium chloride or salt (NaCl) it consists of sodium and chlorine atoms. In atomic terms, the chlorine in the salt has a negative charge, while the sodium has a positive charge. The reality is that they both have the same number of atoms, so we say the salt is “neutral”.

Hydrogen and oxygen in water

On the other hand, we have water molecule (H2O) it consists of two hydrogen atoms and one oxygen atom. And here we have to stop at hydrogen bridges, where the power of salt is understood.

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When you pour salt on ice, some of the salt molecules melt, dissolving the sodium chloride into sodium ions (which, remember, were positive) and chlorine ions (negative). Thus, sodium ions attract oxygen from water, while chlorine ions attract hydrogen.

The key is the hydrogen bonds of water

These hydrogen bonds raise the melting point up to 0 °C if this interaction can occur. It is because of this that the water does not freeze. If the melting point is low, less energy will be needed to melt the ice, which is then converted back into water..

It hits the road
The salt mixture is necessary to lower the boiling point of the ice and thereby maintain the mechanical properties of the road: the adhesion between the tire and the road.

As we all know pure water freezes at 0ºC, but this only happens when the water is, shall we say, “pure”. If something melts, it loses its purity and thus its solidification temperature is lower. So now we have the salt mystery solved.

The use of salt has more and more opponents because of its impact on the environment

Although the use of salt on roads and in cities is a common practice in our country, nWe are not yet aware of the environmental impact this entails.

Effect on plants and animals

And all the salt we throw on the road increases the chlorine and sodium levels in the water that ends up in the ground, che is the main substrate where plants live.

Among many other problems, salt alters the natural environment, causes long-term species decline or the spread of invasive organisms, and also alters nutrient cycling.


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