Freezing-point depression helps to keep roads clear of snow.
It takes just one snowstorm for us to be thankful that our knowledge of science can help us deal with the fierce beauty of nature. Being able to lower the freezing point of water enables us to travel safely on winter roads.
What Is the Freezing Point
The freezing point is the temperature at which water freezes. At normal atmospheric pressure, water freezes at 0° Centigrade.
Freezing-Point Depression
Freezing-point depression refers to the lowering of the temperature at which water freezes. Thus, the ambient temperature needs to be colder than 0°C before water will freeze.
How the Freezing Point Works
Water freezes when the movement of the water molecules slows down due to the cold. This slower movement makes the molecules line up in a crystalline pattern to form ice. However, the addition of a solvent, for example salt, interferes with the ordering of the water molecules. So, though the temperature continues to be 0°C, ice does not form until the temperature drops even further. It needs greater cold to affect the movement of the molecules so a crystalline grid of ice forms.
Significance
Knowing how freezing-point depression works allows us to use the principle to make daily life easier. Spraying salt on snowbound roads help to clear the snow and makes for a safer drive. Home ice cream makers also benefit from freezing-point depression by keeping the machine cool for longer periods.
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