Question

What happens when you spread salt crystals over an icy sidewalk? Why is this procedure rarely used in very cold climates?

Short answer

The transition temperature between the phases will be lower than, implying that the ice on the street will not freeze until the temperature drops to the new phase temperature.

Step-by-step solution

Given information

Salt crystals are spread over an icy sidewalk.

Explanation

We know that water freezes at $0°C$, thus sprinkling salt on the icy sidewalk will lower the phase temperature. As a result, the transition temperature between the phases will be lower than $0°C$, implying that the ice on the street will not freeze until the temperature drops to the new phase temperature.

This approach will not work in very cold nations since the temperature is below the phase temperature of the water and salt mixture, and the mixture also causes concrete damage, so it is only used in very cold countries on rare occasions.