Phase Change
Properties of Matter

Festive Star

Enrichment Activity for 5-11 11-14


What you need

  • Large glass of hot water

  • Pencil
  • Two pipe cleaners
  • Epsom salts
  • Blue food colouring
  • Spoon

Instructions

  1. Cut one pipe cleaner in half. Twist the two halves around the second pipe cleaner to make a six pointed star.
  2. Twist the long point around a pencil so the star can hang from it.
  3. Fill a class with enough hot water so that the star will be completely covered when it's hanging from the pencil.
  4. Add some colouring to the water.
  5. Stirring, add epsom salts to the water until no more will dissolve and wait overnight.
  6. Hang the star in the water and wait overnight.

Results and Explanation

A sparkly star emerges.

The rough surface of the pipe cleaners acts as a nucleation site, encouraging the salt molecules to come out of solution and form crystals. They grow overnight as more and more salt molecules attach to the crystal surfaces.

These experiments have not been specifically safety tested for home use but we believe them to be safe if the instructions are followed. Adult supervision or direction is recommended as appropriate. All experiments are carried out at your own risk.

Phase Change
can be analysed using the quantity Energy
2021 IOP Awards

Teachers of Physics Award

Recognising and celebrating outstanding contributions to the field of physics education.

Learn more