Phase Change
Properties of Matter

Microwave marathon

Enrichment Activity for 5-11 11-14

What you need

  • Ice cubes
  • Tap water
  • Scales
  • A microwave oven
  • Identical microwave-safe cups


  1. Put a few ice cubes into a dry cup and weigh it.
  2. Pour water into another cup until it weighs the same as the first one. (It is dangerous to heat distilled water in a microwave, so use tap water.)
  3. Stand the cups on opposite sides of the oven’s turntable and microwave them. The water should boil before the ice melts.

Results and Explanation

Inside the microwave there's a quickly-changing electric field. Water molecules are slightly charged at both ends, and want to align themselves with this electric field. Because the field keeps changing, the molecules in liquid water are spun back and forth, raising the temperature of liquid quickly. The water molecules in ice are fixed in a crystal structure, and so cant rotate and so the temperature doesn't increase as much.

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
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