* Freezing Point Depression: When you add salt to ice, the salt dissolves in the thin layer of water that forms on the surface of the ice. This dissolved salt disrupts the formation of ice crystals, making it harder for the water to freeze.
* Endothermic Reaction: The process of salt dissolving in water is endothermic, meaning it absorbs heat from the surroundings. This absorption of heat further contributes to lowering the temperature of the mixture.
In essence, rock salt doesn't make the ice itself colder, it makes the surrounding water melt at a lower temperature. This is why it's used to melt ice on roads and sidewalks: the salt lowers the freezing point of water, allowing the ice to melt even when the temperature is below 32°F (0°C).
Important Note: While salt can make ice melt at lower temperatures, it doesn't actually cool the ice down further. The temperature of the ice itself remains at 32°F (0°C) until it melts completely.
