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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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:

Large container filled with water
Objects collected from around the house
Free printable recording sheet (optional)

Procedure:

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.)
Fill a large container with water. (We used a large plastic bin.)
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.
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.)
Repeat this for all the objects.
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?

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!

Tips:

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.

Fill up a giant backyard pool with water and do this experiment with larger items.
For older kids, introduce the terms density and buoyancy to explain what happened.
Place an orange in your container of water to see if it floats. Peel the orange and try it again. What happened?
Try the Floating Egg experiment found on Tinkerlab.
Do our Dancing Raisin science experiment.
Related children’s books: Who Sank the Boat?, The Magic School Bus Ups And Downs: A Book About Floating And Sinking, Floating and Sinking