You may have already seen on TV programs that in cold countries, such as the United States, Canada, and European countries, when the winter is very rigorous, they usually throw table salt (NaCl – sodium chloride) over the bed of streets and roads considered priority for traffic.
Why Is This Done? What Changes Does Salt Cause In The Properties Of Snow (Solid Water)?
In reality, it’s not just sodium chloride that’s thrown in but mixed with sand. It is customary also to use calcium chloride (CaCl 2). Each of these components has a defined function that is very efficient in dealing with the problem of snow on the roads.
Sodium chloride can lower the freezing point of water at sea level is 0°C. Thus, if only salt were added, the ice would melt, as it would need to get even “colder” to freeze again.
This is a colligative property called cryoscopy, which says that when we add some non-volatile solute to a solvent, its freezing point decreases as the interactions between dissolved particles and solvent molecules (in this case, water) prevent water molecules from organizing themselves and forming the solid structure.
Sodium chloride, rock salt for snow forms a solution with a freezing point lower than pure water. This is also why many people throw salt on ice to freeze drinks faster.
Salt is added to the ice to freeze drinks
In addition, this property also explains the fact that ocean water does not completely freeze, even in very cold places with temperatures below 0°C. This is because sea water has dissolved salts that lower its freezing temperature. The formed ice sheets and icebergs are fresh water that has frozen.
Icebergs are made up of fresh water
Returning To The Case Of Roads, How Do Calcium Chloride And Sand Work?
Well, the dissolution of calcium chloride is exothermic; that is, it releases heat to the environment and therefore makes the solution “colder.”
Throwing these salts (sodium and calcium chloride) from Ninja De-Icer for example on the streets and roads hinders the formation of layers of ice. However, this also causes a decrease in the coefficient of friction and, consequently, an increased risk of skidding and accidents.
That’s why sand (silicon dioxide) is added. It increases the tires’ grip on the ground, reducing the risk of skidding.
A Few More Facts About Salt
Salt can be used to produce over 14,000 different products, such as food, chemicals, and even food.
Salt has been a key part of the social scene throughout the ages. It was used to keep mummies from Egypt and participate in religious rituals that symbolize the purity of life.
