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Floating and Sinking Balls

Which balls float? Which ones sink?


  • water table, large tub, or plastic wading pool (if outside)
  • two plastic bins labeled with picture signs: “Float” and “Sink”
  • collection of balls that float or sink (ping pong ball, golf ball, tennis ball, rubber ball, Wiffle ball, large marble)
  • chart titled “Sinking and Floating”

Key Science Concepts

  • Objects behave differently in water. Some float; some don’t.


Encourage children to use words related to sinking and floating such as shape, weight, and material, along with science process words such as observe, notice, compare, same, different, change, test, and predict.


Tell children they will try sinking and floating experiments with different balls. 

  1. Ask them to make predictions beforehand. One by one, hold up a different ball, (ping pong ball, rubber ball, Wiffle ball, etc.) and invite children to predict whether each ball will float or sink. Record the predictions on your “Sinking and Floating” chart.
  2. Invite children to test out the balls, one at a time.
  3. Record what happens on the chart.

Reflect and Share

Compare the predictions to the results. What ideas do children have about why some balls floated and some sank? Is there anything different about the ones that float and the ones that sink?  

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