What Dissolves Road Salt?

Chemical Properties

• There are many different types of salts that feature different chemical compositions. Road salts are generally composed of sodium chloride. This salt features what is known as an ionic composition. This means it is composed of both a positively-charged and negatively-charged atom. In the case of sodium chloride, the sodium atom is positively charged, while the chlorine atom is negatively charged. It is the attractive force of these negatively charged particles, which bonds them together and creates the solid salt substance.

Dissolution

• Salt possesses a chemical property known as solubility, which means it can be dissolved in water. When added to water, the sodium and chlorine elements of the salt bond to the elements of the water. This breaks the ionic bond of the particles. When the ionic bond is broken, the sodium and chlorine elements will attach to the hydrogen and oxygen elements of the water, which dissolves the solid salt compound.

Ice Melting

• Since ice is simply water that is at a low enough temperature to freeze, salt will dissolve into ice the same way that it dissolves in water. When water freezes, the water particles align and remain in a more stable position. When salt is added to water, the water particles cannot easily reach the stable state needed to create ice due to the presence of the salt elements dispersed throughout. This effectively lowers the freezing point of water. Therefore, when road salt is poured onto ice, it dissolves into the ice and converts it back into water.

After Effects

• After road salt converts ice or snow back into water, it remains dissolved within the water. Most of the salt will simply wash away when the ice water flows off of the road. However, not all of the salt will dissolve perfectly into the ice. Excess salt will collect at the bottom of the water it is placed in, in this case on the roadway itself. This is why its common for roadways to be coated with a dusty layer of salt after winter storms. The excess road salt will dissolve naturally when future precipitation events occur.