Science Fishing – Catch an Ice Cube with a Piece of String

It’s been freezing in Denver over the past week. We are surrounded with snow and ice. Here’s a little activity for the kids. Take a bowl of ice cubes and set it in front of them. Tell them you want them to go fishing for the ice cubes. Their challenge? Pick up an ice cube with a piece of string.

We all know that sprinkling a little salt on ice will melt the ice. But how does it work? Salt dissolves in water easily. The salt molecules sodium ion and a chloride ion (sodium chloride) disassociate in the water and break apart. They confuse the water molecules so they can’t freeze as easily. To start your fishing trip, start with a wet string and a little salt. Lay the string over the ice cube and sprinkle it with the salt. Wait for a few minutes while the reaction takes place. As the salt melts the ice, the string moves down into the ice a little bit. Then fresh water moves up and refreezes over the string. You can then pick up the ice cube with the string.

Think about this experiment on a larger scale – how does sodium chloride or magnesium chloride work on melting ice on the roads in winter? Watch the video for the answer.

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