Water that Floats and Sinks

Properties of water

Why does water that is floating suddenly begin to sink. This water cycle activity shows you what happens to ice cubes when they begin to melt when floating in oil.


  • Red, blue or green food coloring
  • Ice cube tray
  • Bottle of salad oil
  • Plastic container


  1. Mix food coloring with water so that it turns a dark color.
  2. Freeze the colored water in an ice cube tray overnight.
  3. The next day pour the salad oil into a container that is deep
    enough to float an ice cube.
  4. The ice cube should be at least 3 inches
    from the bottom.
  5. Watch what happens as the ice cube melts for about 5

In this water cycle activity book you will learn about many properties of water. Some of the activities in the book include Penny Drop, Great Ice Cube Race and Exploding Colors. The 46 page book is packed with many other fun activities for kids.

Click for More Information and to Order

Science behind the activity

The ice cube floats in the oil because water expands when it freezes and
becomes lighter than the salad oil. As the ice cube melts and turns into a liquid it contracts.

The water becomes
heavier than the salad oil forming round balls of water suspended in the
salad oil as it drifts to the bottom of the container.

The water forms small
balls of liquid because the water molecules are attracted to each other and not the oil. This causes surface tension to form on the outside of the water molecules. The shape they form, a ball, is the most compact shape it can form as it drifts down through the oil.