Yes, salt water can freeze, but it freezes at a lower temperature than fresh water.
Here's a breakdown:
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Freezing Point Depression: The presence of salt (sodium chloride) in water disrupts the formation of ice crystals. This disruption lowers the freezing point. This phenomenon is known as freezing point depression.
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Freezing Temperature of Salt Water: While fresh water freezes at 32°F (0°C), seawater typically freezes at around 28.4°F (-2°C). The exact freezing point depends on the salinity (salt content) of the water. Higher salinity means a lower freezing point.
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Sea Ice Formation: A significant portion of the ocean, around 15%, is covered by sea ice at some point during the year. This ice is formed from freezing salt water. When seawater freezes, the salt is largely excluded, resulting in sea ice that is less salty than the original seawater. The rejected salt creates a concentrated brine that can sink, further influencing ocean currents.
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Practical Applications: The lowered freezing point of salt water is why salt is used on roads and sidewalks in winter to prevent ice formation. The salt dissolves in the water, creating a saltwater solution that has a lower freezing point than pure water, thereby inhibiting ice formation.
In summary, while salt water does freeze, the presence of salt lowers its freezing point compared to fresh water. The freezing point is dependent upon the amount of salt dissolved in the water, but is usually around 28.4°F (-2°C).
