Salt freeze

Cold secrets of salt.

20 minutes


  • Carefully review the general safety advice on the back of the box cover before starting the experiment.


  • Dispose of solid waste together with household garbage.

Scientific description

If we cool water to 0 degrees Celsius (32 degrees Fahrenheit), it will turn into ice, but if we continue to cool the ice, we will not notice any further changes in it. However, the temperature in your freezer is noticeably below freezing. Therefore, when you remove your ice from the freezer, it has a temperature below 0 degrees Celsius. It turns out that the freezing temperature of salt water is also below 0 degrees Celsius, which is why water in salty oceans needs much lower temperatures to freeze than fresh water.Here, when we set the ice cube on the salt, the ice starts to melt, mixing with the salt. This creates a puddle of salt water at the bottom of the Petri dish, which the ice on top can continue to cool below 0 degrees Celsius. After some time, the ice cube will cool the salt water so drastically that the salt water will take heat from the drops of water under the Petri dish and freeze them. The frozen water drops under the Petri dish then keep it stuck to the box.