You’ll need

  • Empty plastic bottles with lids (at least 4)
  • A bathtub or sink
  • Water

What to do

Warning!

Always supervise children when they’re around water. Small objects, such as bottle lids, can be choking hazards – make sure lids are screwed on tight, and keep loose lids out of reach of children.

  1. This is best done during regular bathtime.
  2. When you child is in the bath, hand them an empty bottle without a lid. Let them explore what happens when they play with it in the water. Ask them if they can make bubbles.
  3. Take another empty bottle and screw the lid on tightly. Let them explore what happens to this one in the water. Ask them if they think this one will sink.
  4. Take 2 more bottles and fill one completely and screw the lid on tightly. Half-fill the other and screw the lid on tightly.
  5. Encourage them to experiment with which bottle is the hardest to push under water.
  6. Your child will love it when you dunk the empty bottle in the water and let go and the bottle pops up out of the water again!

Questions to ask

Which bottle sinks and which bottle floats?

How can we get this bottle to sink/float?

How many bubbles does the bottle let out?

Try changing the amount of water in the closed bottles and see what happens!

What's happening

Children learn about shapes, weight and volumes by playing with different amounts of water in bottles. This activity lets them experience different levels of buoyancy based on the different amounts of air and water in each bottle. You can explore the concept of mass and ask them what is heavier – air or water? And how is that shown by the bottles?