Virtual Museum – Sink or Float


Sink or Float!

Have you ever wondered why some things sink and some things float? Let’s explore the concepts of density better known to children as sink or float! An object that sinks goes below the top of the water and an object that floats stays on top of the water. This simple experiment will encourage your child to make predictions and observations. Through their observations they will learn that more dense objects sink and less dense objects float.


  • Large container such as a plastic tub, bucket, sink or bathtub
  • Water
  • Household objects such as a spoon, comb, sponge, bar of soap, rock, leaf or a flower
  • Optional: paper and pencil for recording




  1. Fill a large container with water.
  2. Gather objects from around the house or garden.
  3. Observe the object and have your child describe what they notice.
    • What is this?
    • Is it heavy or light?
    • Use one of the objects to demonstrate what happens when something sinks or floats. Introduce the vocabulary of “sink” and “float” as you test the object out in the water.
  4. Make a prediction: What do you think will happen when we put it in the water?
    • Will the object sink to the bottom of the container?
    • Will the object float on the top of the water?
  5. Have your child drop the object in the water.
  6. Together with your child, sort the objects into categories of sink and float.
  7. Optional: Record your findings on a piece of paper.


  • What happens when something sinks?
  • What happens when something floats?
  • What do you notice about an object that sank?
  • What do you notice about an object that floated?


  • Supports early math and science skills by sorting objects by sink and float.
  • Encourages prediction making as children think about will happen to an object when placed in water.
  • Develops observational skills by recognizing whether an object will sink or float in water.


Try making boats from different recycled materials. What materials sink and what materials float? Encourage your children to experiment with different shaped boats. Make sails or other accessories for your boats. Does adding or subtracting materials affect how the boats sink or float?