1. Freezing Point Depression

* Pure water freezes at 0 degrees Celsius (32 degrees Fahrenheit).

* Salt (sodium chloride) dissolves in water, creating a solution.

* Solutions have a lower freezing point than pure water. This is called freezing point depression.

2. How Salt Affects Ice

* Salt dissolves in the thin layer of water that naturally forms on the surface of ice.

* This dissolving process absorbs heat from the surroundings, including the ice itself.

* The ice loses heat, causing its temperature to drop below its normal freezing point.

* To reach a new equilibrium, the ice melts to become part of the saltwater solution.

3. The Effect of Concentration

* The more salt you add, the lower the freezing point of the solution.

* This is why rock salt (which is mostly sodium chloride) is more effective at melting ice than table salt. Rock salt has a higher concentration of sodium chloride.

4. Important Note:

* Salt only melts ice that is already at or below its freezing point. If the ice is already above its freezing point, salt won't have any effect.

In summary, salt lowers the freezing point of water, causing ice to melt because it absorbs heat and brings the temperature down below its freezing point.