Science for Kids: Sink or Float (with Free Printable)

Kids love discovering which items will sink or float! It’s a great hands-on science activity for kids of any age and really gets kids thinking and predicting. Here’s how we set up our sink or float science project, as well as a free printable kids can use to record their observations.

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Sink or Float Science Activity for Kids w/ Free Printable (


This experiment was actually initiated by Lucy herself! She had approached me one day and asked if I could help get her a container of water to test out some objects she had collected.

Kids are naturally curious about floating and sinking, and this science activity provides the opportunity for children to make predictions and observations about floating and sinking with minimal help.  (This post contains affiliate links.)



Materials for Sink or Float Science:

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  1. Walk around your house with your child and collect items you’d like to test out. (We collected these things: bristle block,  plastic toy, crayon, cork, a spoon, and a rock.)
  2. Fill a large container with water. (We used a large plastic bin.)
  3. Find a place to conduct the science experiment where your child can easily reach the bin and where you don’t mind a bit of water possibly getting out.
  4. Have your child choose one object at a time. Do you think it will sink or float? Why?  Have your child place the object in the water and observe what happens. (Optional: Record the result on the recording sheet. You can have your child draw a picture or write the name of the object or model writing and drawing the object yourself.)
  5. Repeat this for all the objects.
  6. Why do you think some objects floated and some sank? Is there anything the same about the objects that floated? How about with the objects that sank? 

testing sinking or floating


Lucy had so much fun with this! It was fun to sit back and watch her excitement and curiosity grow as the activity went on. At one point she even came up with a new question, “I wonder what will happen if I push the floating things down to the bottom. Maybe they will stay there.” She discovered they still floated right back up!

close up of experimenting


  • We took our experiment outside. That way there was no worry about a mess being made.
  • I left this outside for a few days for the kids to experiment with on their own during play time.
  • This would also be a fun center in a school classroom!

Sink or Flat Science for Kids

Want to go even further?

Even more activities to inspire creativity and critical thinking for various ages.



Find more STEM activities in our ebook! Learn more about it here, or buy it now here!

Fizz, Pop, Bang! 40 Playful Science and Math Activities for Kids


Sink or Float Science: Fun hands-on science activity for toddlers, preschoolers, and kindergarteners! Perfect for summer! (Includes free printable recording sheet) ~


  1. I love it! We tried something similar a few months ago, I loved the way they were doing hypotheses and predictions about what would happen with different materials, and how they were surprised to see that some of their assumptions were not correct. Their curiosity and adaptability is fabulous.

  2. We love this game! Every so often my 4-year-old will still come up to me with some random object and say, “I want to experiement – Will this sink or float?”

  3. Thank you I have been thinking about doing more science with my boys since our germination experiment and this is so quick and simple to set up.

  4. That’s awesome! My 3-year old initiated the same experiment after breakfast last week…though he wasn’t as tidy about it as Lucy! I’m featuring this post at this week’s linky–thanks for sharing it at Teach Me Tuesday at Preschool Powol Packets!

  5. Featuring this at Family Fun Friday!

  6. I love the expressions on her little face! Such a fun way to explore science! Am featuring on my Kid’s Co-Op post this week…thanks for sharing with us!

  7. I love that Lucy initiated this investigation and that you followed her lead. Thanks for linking up to Discover & Explore. I’m featuring this post today.


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