Sink or Float Experiment
By Arlington Parks & Recreation
Posted on April 15, 2020, April 15, 2020

Water is such a wonderful resource as it can be used for all types of play, exploration, and learning.

A sink or float experiment is a simple physics experiment that will encourage your child to make predictions and observations about buoyancy and density. Through testing and observing, they’ll learn that buoyant objects float and dense objects sink.

What you’ll need: 

*Indoors, kids can do this activity at the kitchen sink, in the bathtub or on the floor with a tub or basin filled with water.

Setting up the Experiment:

  • Fill your bucket or tub with water and take it outdoors if you can. (less clean up)
  • Have your child gather items they find in your yard or on a nature walk. Examples: Rocks, Sticks, Tree Bark, Fallen Leaves, Pinecones, Pecans, Fallen flowers.
  • Take the items back home and talk about which items your child thinks will sink and which items will float.
  • Fill out your Sink or Float With Nature sheet listing your items you’ve found.

Conducting the Experiment:

  • Time to test the items! Have your child select an item for testing.
  • Encourage them to hold the object in their hands to feel how heavy it is and chat about what they think will happen.
  • Record your child’s prediction.
  • Have them place the item in the water to check their prediction.
  • Record the result and feel free to write down anything they observe.

Results and Conclusion

  • Talk about their predictions and what they learned.
  • Before explaining why items sink or float, ask your children why they think an object sinks or floats.
  • Did anything surprise them?
  • Then, explain that items sink or float based on their density. Density is determined by how close or far apart molecules are within an item. Molecules are tiny and only visible by a microscope. You can refer to this article to help explain this to your kids.

Once you have prompted their learning by explaining the science behind the activity, allow your children to replicate the experiment as many times as they please. This will help to solidify their knowledge and reap the benefits of play-based learning.

Don't forget to share photos of the experiment in action by tagging us @arlingtonparks or using #NaturallyFun!

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