Dissolving a solute in a solvent lowers the solvent's freezing point — the same principle behind salting icy roads.
Dissolving a solute in a solvent lowers the solvent's freezing point — the same principle behind salting icy roads. The amount of depression depends on how many particles the solute breaks into (the van't Hoff factor), the solvent's cryoscopic constant, and the solution's molality.
Dissolving salt (i=2) in water (Kf=1.86) at 0.5 mol/kg molality. ΔTf = 2 × 1.86 × 0.5 = 1.86°C — the solution freezes at about −1.86°C instead of 0°C.
It's the decrease in a solvent's freezing point caused by dissolving a solute in it — for example, salted roads melt ice because the salt lowers water's freezing point.
ΔT = i × Kf × m, where i is the van't Hoff factor, Kf is the solvent's cryoscopic constant, and m is the molality of the solution.
Antifreeze (ethylene glycol) dissolved in a car's coolant lowers the freezing point of the water-based coolant, preventing it from freezing and damaging the engine in cold weather.