Adding salt to water impacts which point concerning phase change?

Adding salt to water affects the freezing point by lowering it, a phenomenon known as freezing point depression. This occurs because the dissolved salt ions disrupt the formation of ice crystals, which are necessary for water to freeze. The presence of salt ions means that more energy (in the form of a lower temperature) is required for the water molecules to arrange themselves into the structured solid form of ice.

As a result, when salt is added to water, the temperature must be reduced below the normal freezing point of 0 degrees Celsius (32 degrees Fahrenheit) for the liquid to actually freeze. This principle is commonly observed in applications such as de-icing roads in winter, where salt is used to prevent ice from forming, thereby helping to maintain safer driving conditions.

By contrast, the other options do not accurately describe the effects of adding salt to water. The boiling point actually increases when salt is added (boiling point elevation), and the cohesion of molecules does not increase; it may even decrease slightly as the salt disrupts intermolecular forces. Additionally, viscosity typically increases when salt is added rather than decreases.