How do the dissolved salts in seawater affect its freezing point and boiling point?

Dissolved salts in seawater, such as sodium chloride, significantly alter the physical properties of water through a phenomenon known as colligative properties. These properties depend on the number of dissolved particles rather than the specific nature of the substance itself.1

• Freezing Point Depression: The presence of salt makes it more difficult for water molecules to bond together into a rigid, solid structure. By interfering with this process, dissolved salts lower the freezing point of seawater compared to that of pure water. This concept is known as freezing point depression.23
• Boiling Point Elevation: Conversely, the presence of dissolved solutes increases the boiling point of seawater, making it higher than that of pure water.2

When sodium chloride dissolves, it dissociates into individual sodium and chloride ions, which interact with water molecules through hydration. These interactions effectively disrupt the standard behavior of pure water, resulting in these measurable changes to its phase-change temperatures.34