The answer is called freezing-point depression.
When a solute is added to a solvent the freezing point is lowered. This is a colligative property, which means that the depression of the freezong point depends on the number of perticles dissolved.
The formula to calculate the freezing-point depression is:
ΔTf = i * Kf * m
Where m is the molality of the solution, Kf is the cryogenic molal constant (specific for any solvent) and i is the called VAn't Hoff factor.
The Van't Hoof factor accounts by the number of particles dissolved. When the solute is not ionic it is 1.
