Fresh water freezes at 0°C. The presence of salt lowers the freezing point and the higher the salt content in the water, the lower the freezing point.
That is why salt is often used to Icy roads in winter. Stops water from freezing on roads, making driving safer.
Sea water contains salt. It will freeze, but requires lower temperatures than fresh water. Typically, only very cold parts of the sea, such as the Arctic and Antarctic, are cold enough for sea water to freeze.
Seawater freezes at about -1.8°C.
Why is sea water salty?
Salt in seawater is mainly caused by mineral ions entering the water. Carbon dioxide in the air dissolves in rain, making it acidic. Acid rain falls on rocks and begins to erode them, releasing mineral salts (including sodium and chloride) into the sea. Sodium chloride is the chemical name for the salt we eat!
The Dead Sea is an example of a body of water that has become very salty. It's so salty that visitors can sit on the surface!
Did you know?
Blocks of frozen seawater are known as icebergs.
Humans cannot drink salt water.
When seawater freezes, salt molecules are pushed beneath the surface of the ice. This means that polar ice is actually fresh water!
Does salt water freeze scientific research?
You can find out if salt water freezes in your kitchen! This simple hands-on science activity takes only a couple of hours and only requires a few basic supplies.
You will need to
Two small, empty plastic bottles or small bowls
Water
Salt
Freezer
Instructions
Place the same amount of water in each bottle.
Add two tablespoons of salt to a bottle and label it saltwater.
Label the second bottle, running water.
Place both bottles in the freezer and check them every 30 minutes.
You should find that salt water freezes more slowly than tap water.
Does salt water freeze? Research Template
My handy experiment template guides you through the investigation with easy-to-follow instructions and space for results.
More scientific experiments using salt
Use salt to lift a piece of ice with a rope. In this clever trick, the salt melts the ice around the thread. The ice then refreezes on the rope, allowing the ice cube to be lifted.
Find out how chill a drink with ice and salt.
Make a salt lava lamp. This is a fun take on the more traditional lava lamp.
Last updated on May 16, 2024 by Emma Vanstone
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