Ice Tunnels | Try this at Home!

What you need:
Water
Freezer-safe bowl (metal or plastic)
Freezer
Food coloring
Salt
Tray

What you do:
Step 1: Fill a freezer-safe plastic or metal bowl with water and place it in the freezer. Remove the bowl from the freezer once the water has turned into ice.
Step 2: Remove the frozen dome of ice from the bowl and place it flat-side-down on the tray.
Step 3: Sprinkle salt onto the dome and wait for about three to five minutes.
Step 4: Drip food coloring onto the ice and watch as the tunnels appear before your eyes!

What's going on?
The freezing point of water is 0oC (32oF), but salt can make it even lower. This allows salt water to remain in a liquid state at a temperature colder than regular freshwater could. This is an example of something called “freezing point depression.” Sprinkling salt on the ice dome slowly melts the ice, creating tiny tunnels. The food coloring sinks into these tunnels allowing you to see them.

Now try this:
Try using different kinds of salt such as kosher salt or rock salt. What happens when you dump the salt instead of simply sprinkling it? Can you create patterns with the salt?

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