Science & TechFact
Why road salt melts ice while staying ice cold.
Dissolved particles disrupt the ice crystal lattice, so salt water freezes below 0 °C. Salt on ice dissolves into the thin water film on the surface and lowers its freezing point there, so the ice keeps melting. Table salt works down to about −21 °C; below that even a saturated solution freezes. In severe frost, only grit or calcium chloride helps.
Useful: The same trick chills ice cubes with salt below zero, ideal for making drinks ice cold in minutes.
Source: en.wikipedia.org