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

sink or float science

Welcome to another Science Invitation Saturday where we focus on fun science for kids to promote curiosity and critical thinking.  For our last science invitation we turned pennies green!  This week we’re going to experiment with sinking and floating. In this science experiment for kids, you’ll be placing various objects in a large container of water to see if they sink or float.

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. I think kids are naturally curious about floating and sinking, and this invitation provides the opportunity for children to make predictions and observations about floating and sinking with minimal help.  




  • large container to filled with water
  • objects collected from around the house
  • free printable recording sheet (optional)

Screen Shot 2013-07-18 at 7.19.52 PM



  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 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

the results

Lucy had so much fun with this! It was fun to sit back and watch her excitement and curiosity. 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

pushing objects down


  • 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!


Want to go even further?

Even more activities to inspire creativity and critical thinking for various ages. (This post contains affiliate links to Amazon for your convenience.)

 sink or float~ science for kids




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  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.
    Pinkoddy recently posted…Page 3 Girls or SAHM – Are they both bad role models for girls?My Profile

  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!
    Carla recently posted…Polar Bear Fur Experiment & Poppins Book NookMy Profile

  5. Featuring this at Family Fun Friday!
    Monica recently posted…Family Fun Friday Week 29My Profile

  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.
    Shaunna @ Fantastic Fun and Learning recently posted…Sink or FloatMy Profile


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