Why Salt Melts Ice
When salt is mixed with ice it lowers the freezing point. Usually water freezes at 32° F (0° C), but when it is mixed with salt it lowers the freezing point significantly. This simply means the ice melts. We have used this same trick to make yummy treats like fruity ice slush and easy homemade ice cream!
For our experiment today we will use this phenomenon to do a little trick I like to call “Fishing for Ice”.
Total Time: Less than 5 minutes
Safety Concerns: None. All ingredients are safe and edible, though perhaps not very tasty when mixed together!
Materials You Need:
Cup full of water
A few ice cubes
A piece of string
- Place the ice cubes in the cup of water. They will float on top.
- Try to “fish” for an ice cube with the string. It won’t “catch” anything.
- Place the string in the water and across the top of the ice cubes.
- Now sprinkle a little bit of salt across the ice cubes. Wait for a minute or so.
- Pull the string out and see what you caught!
When salt is sprinkled over ice it melts. However, when it is used in such a small amount, like in our experiment, the water around the ice freezes again quickly. This means that the string gets trapped as the water around it refreezes, thus making it stick to the ice. We were able to freeze all of our ice cubes to one piece of string. How about you?