Freezing Point Depression — Passage

Freezing point depression is a fascinating scientific phenomenon that occurs when dissolved substances lower the temperature at which a liquid freezes. This concept is fundamental in understanding how mixtures behave and has numerous practical applications in our daily lives, from winter road safety to food science.

Freezing point depression occurs when a substance, like salt or sugar, is added to a liquid, usually water. This causes the liquid to freeze at a lower temperature than normal. Normally, pure water freezes at 0°C (32°F). But if you add salt, it may not freeze until it gets colder—sometimes down to -10°C or lower, depending on how much salt is added.

This happens because the added particles (like salt) get in the way of the water molecules as they try to form solid ice. It becomes harder for them to lock into the solid structure, so the water needs to get colder before it can freeze.

Freezing point depression is a physical change and an example of how mixtures can affect the properties of a substance. It doesn’t change what the water or salt is made of—it just changes how they behave when combined.

This effect is used in real life all the time:

●     Road safety: Salt is spread on icy roads to lower the freezing point of water and melt ice.

●     Homemade ice cream: Salt is added to ice around the ice cream container to help it freeze faster.

●     Car antifreeze: Special liquids are added to water in car engines to stop it from freezing in cold weather.
 

Understanding freezing point depression helps us stay safe and solve everyday problems using science!

Fun Fact: The coldest temperature ever recorded on Earth was -89.2°C in Antarctica—and even there, salt water stayed liquid!