1. The freezing point of salt water is lower than that of water because salt dissolved in water forms an electrolyte solution, which has a lower freezing point than a pure solvent. At the same temperature, salt water is harder to freeze than water.

2. The freezing point of salt water decreases as the concentration of salt increases. It is because the ions of salt will combine with water molecules to form hydrated ions, and these hydrated ions will hinder the orderly arrangement of water molecules, thus lowering the freezing point of salt water. So salt water does not freeze easily.