The Dilemma of Using NaCl Salt to Melt Snow on Highways Every winter, governments in subtropical and cold countries face a dilemma in dealing with frozen snow on highways. One of the most commonly used methods is to sprinkle salt (NaCl) on the road surface. This method utilizes the principle of lowering the freezing point of a solution, one of the colligative properties that occurs when a non-volatile solute is added to a solvent. However, the use of road salt raises pros and cons involving safety, cost, and environmental impact. When NaCl salt is spread on snow or ice, the salt dissolves in a thin layer of water that forms on the ice surface. NaCl salt is completely ionized in water with the equation:

  The presence of these ions in the solution causes a decrease in the freezing point of water. The decrease in freezing point can be calculated using the formula:

  Where ΔTf is the freezing point depression (°C), Kf is the molal freezing point depression constant of water (1.86 °C kg/mol), m is the molality of the solution, and i is the van't Hoff factor (for NaCl, i = 2 because it ionizes into 2 ions). Pure water freezes at 0°C, but a 10% salt solution can lower the freezing point to around -6°C, and a saturated NaCl solution (23%) can lower the freezing point to -21°C (Wikipedia, 2025).

  According to Solomon et al. (2023), in the United States, approximately 24.5 million tons of road salt are used annually at an average cost of $50-70 per ton (equivalent to Rp 1,500,000 per ton). Research by Kuemmel & Rashad (1992) shows that the use of road salt reduces accidents by up to 88%, injuries by up to 85%, and accident costs by up to 85%. Other alternatives available are calcium chloride (CaCl₂) at a price of $150-200 per ton (Rp 4,200,000 per ton), and magnesium chloride (MgCl₂) at a price of $3,800,000 per ton. Calcium chloride has a van't Hoff factor i = 3 because it ionizes into one Ca²⁺ ion and two Cl⁻ ions, making it more effective at lowering the freezing point to -51°C at saturated concentration. However, it causes a high level of corrosion to metal and concrete infrastructure.

  Environmental impact is a serious concern. The Cary Institute of Ecosystem Studies (2023) reports that 90% of the salt in the Hudson River tributaries comes from road salt. Chloride concentrations in rivers and lakes near salted highways increase up to 100 times compared to natural conditions. The U.S. Environmental Protection Agency, in its 1988 water quality criteria document, set the safe limit for chloride in freshwater at 230 mg/L for long-term protection of aquatic life and 860 mg/L for short-term exposure (U.S. EPA, 1988). However, in many urban areas, chloride concentrations have exceeded 1000 mg/L, causing the death of fish, amphibians, and aquatic plants. In addition, sodium ions from salt can replace important nutrients such as calcium and magnesium in the soil, disrupting vegetation growth along roads (Minnesota Pollution Control Agency, 2019). 

Discuss with group members to practice the following argumentation skills!

Question:

Based on the above reading, should the government continue to use salt (NaCl) as the primary method for melting ice and snow on highways?

To practice making arguments, based on Toulmin, they consist of a claim, data, warrant, backing, qualifier, and rebuttal.

Instructions: