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The snow melting principle of snow melting agents

2024-01-10

After being dissolved in water (snow), "chloride based" snow melting agents have a freezing point below zero degrees. For example, sodium chloride snow melting agents (the main component of table salt) have a freezing point of -10 ℃, calcium chloride around -20 ℃, and acetic acid can reach around -30 ℃. The dissolution of salts requires not only heat absorption, but also a function of reducing the freezing point of saltwater, making it difficult to form ice again after dissolving salt in snowwater. In addition, after the snow melting agent dissolves in water, the ion concentration in the water increases, causing a decrease in the liquid vapor pressure of water, but the solid vapor pressure of ice remains unchanged. In order to reach the state of solid-liquid vapor pressure of the mixture of ice and water, ice dissolves. This principle can also explain the reason why salt water is not easy to freeze.

We know that water is a special substance, that is, its density decreases when it freezes (the density of a substance in its solid state is generally higher than that in its liquid state). Therefore, the higher the pressure, the lower the melting point of ice. It is common to see that snow tends to melt easily in areas where the wheels have run over. After sprinkling snow melting agent on a snowy road surface, it is easier for the snow to melt after being crushed by vehicles. In summary, sprinkling snow melting agent is beneficial for snow removal