Icy Trick

ThinkStretch Icy Trick

Icy Trick

Icy Trick 540 400 admin

Challenge your students and children with this icy trick.  Hand them a piece of string and tell them to get the ice cubes out of the glass without getting their hands wet!  Is it possible?  You can if you know the science behind it…

What you need:

  • A glass of water
  • Ice cubes
  • A piece of string
  • Salt

What you do:

  1. Put the ice cubes into the glass of water.
  2. Place the string on the ice cubes. Hang the ends over the edge of the glass.
  3. Leave the string on for a minute or two.
  4. Pull on the string.  Can you get the ice out? Hmm..
  5. Repeat step 2
  6. Sprinkle salt on the string and ice cubes, and let the glass stand for about 5 minutes.
  7. Now remove the ice cube from the water just by lifting the string.

What’s happening?

Is the salt sticky?  magic?  Not quite.  The salt lowered the freezing point below the usual 32 degrees, so the ice melted a little and trapped the string and then refroze again!  It wasn’t the ice but the unusually cold water that was making this science magic!