The correct answer is option 1. Decrease the freezing point.
Salt is commonly used to clear snow on roads because it lowers the freezing point of water. When salt is spread on icy or snowy roads, it mixes with the snow and ice to form a saltwater solution. The presence of salt in the solution disrupts the normal freezing process, preventing the formation of solid ice at temperatures below the usual freezing point of pure water.
This process is an example of freezing point depression, a colligative property. By lowering the freezing point of the solution, the ice on the roads melts at a lower temperature, making it easier to remove and improving road conditions.
Additional Information:
Let us go into more detail about how salt is used to clear snow on roads and its impact on the freezing point of water.
Freezing Point Depression:
When a solute, such as salt (NaCl), is added to a solvent, like water (H₂O), it disrupts the normal freezing point of the solvent. This phenomenon is known as freezing point depression, and it's one of the colligative properties of solutions.
Colligative Properties:
Colligative properties are properties that depend on the number of solute particles in a solution, not the nature of the solute particles. Freezing point depression is one such colligative property.
How Salt Works on Snowy Roads:
1. Formation of Saltwater Solution: When salt is spread on icy or snowy roads, it comes into contact with the ice and snow.
2. Dissolution: The salt dissolves in the thin layer of liquid water that may be present on the icy surface or is formed by the initial melting caused by the salt.
3. Freezing Point Depression: The presence of dissolved salt in the water lowers the freezing point of the solution. The more salt that dissolves, the lower the freezing point becomes.
4. Melting of Ice: As a result of the freezing point depression, the ice on the road starts to melt even at temperatures below the usual freezing point of pure water.
5. Prevention of Ice Formation: The saltwater solution remains in a liquid state at lower temperatures than pure water would, preventing the reformation of solid ice.
Factors Influencing Freezing Point Depression:
The extent of freezing point depression depends on the concentration of the salt in the solution. More salt leads to a greater freezing point depression.
Benefits of Salt for Snow Removal:
Easier Removal: The melted ice is easier to remove mechanically (e.g., by plowing or shoveling) from the road.
Improved Traction: The application of salt can also improve traction on the road by reducing the slipperiness caused by icy surfaces.
Environmental Considerations:
While salt is effective in melting ice, there are environmental concerns associated with its use. Excessive use of salt can lead to environmental pollution and harm aquatic ecosystems. Therefore, there is a balance to be maintained in its application for effective snow and ice removal without causing undue environmental impact. | 
