Why does salt water have a lower freezing temp.?

Salt dissolved in water changes it's freezing point (and boiling point by the way). Ice forms from water when a certain percent of the water molecules bond into a large sphere-like structure. (Side note: this is also why ice expands - the structure is larger than all the molecules floating free.) The salt interferes with the bond formation, so it needs to get colder for the large sphere structures to form, thus salt water freezes at a lower temperature.

HELLO......... water boil in a higher temperature with salt. it`s because of the solution`s coligative the solutions boiling point is always higher than water`s boiling point, and their freezing point is always lower than water`s freezing point