Phase Change
Properties of Matter

Sew an Ice Cube

Enrichment Activity for 5-11 11-14

What you need

  • Salt
  • A cup of cold water
  • 20cm of sewing thread
  • An ice cube


  1. Float the ice cube in the cup of water
  2. Lay one end of the thread (or a loop) on top of the ice cube
  3. Sprinkle a little salt over the top
  4. Wait one minute then gently lift the thread

Results and Explanation

Salt lowers the melting point of water so the ice melts. But the water quickly refreezes, trapping the string in place.

Phase Change
can be analysed using the quantity Energy
IOP DOMAINS Physics CPD programme

Electricity CPD videos

Our new set of videos gives teachers and coaches of physics a preview of the training we offer ahead of this term's live support sessions.

Find out more