When an antifreeze like salt is used, the freezing point of a solution is lowered. the amount by which it is lowered is called the

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.