Sink or float? A hands-on density activity for kids

I have been teaching STEAM (integrated science, technology, engineering, art, and math) classes for homeschoolers over the last two years. My classes often incorporate a wide range of ages learning a particular topic together with as much open-ended exploration as possible.

One class I will be teaching this year is focused on the concept of density. To prepare for my class, I put together a comprehensive Density STEM Pack with nine different activities that build upon each other to progressively develop students’ understanding of density.

The fourth activity in my Density STEM Pack is a sinking and floating activity that gives kids an opportunity to put their knowledge about density to the test.

Further, this activity builds basic scientific skills by having children make predictions, test their predictions, and then record the results of their tests in an organized fashion.

Lessons on sinking and floating are great to do with children as young as preschool. And indeed, the activity I share below can easily be adapted for preschoolers or kindergarteners. But it can be just as fun for older kids too.

Note: Find more STEM activities on my Science Activities for Kids page!

I set up our Sink or Float? activity in the back yard one afternoon by putting out a table with several objects on it. The objects I chose for this particular experiment were:

A whole watermelon
A piece of watermelon
A whole orange
A piece of orange
A banana
A rock
A crayon
A coin

Next to the table I placed a large bucket of water.

Both kids had their own Sink or Float? worksheet from my Density STEM Pack.

Their first task was to feel each object and predict whether it would sink or float when placed in water.

Once they had recorded their predictions, the kids took turns placing the objects into the bucket of water.

Look! It floats! 🙂

After placing each object in water, the kids recorded their observations on their worksheets.

Afterwards, I was able to review their worksheets and we discussed which predictions they had been correct about and which predictions they had not been correct about. We were all surprised, for example, to find that the crayon sank rather than floated.

We also learned that a whole orange will float, but a slice of orange with the peel and pith completely removed will sink. Whoa! (For older kids, this observation would be a great way to introduce the notion of combined density, or the idea that two objects of different densities – like the orange flesh and the orange peel – can combine to create a density that is different from the individual densities of the component parts.

Here is a sneak peak at the teacher instructions, student instructions, and student worksheet for the Sink or Float? activity:

Sink or Float?
teacher instructions

Does it sink or float? A hands-on science activity for learning about density #STEM #STEAM || Gift of Curiosity

Sink or Float?
student instructions

Sink or Float?
student worksheet

Who is the Density STEM Pack appropriate for?

The activities in the Density STEM Pack can be adapted and used with children from preschool through middle school to have fun and learn important concepts about density. The student worksheets provided for these activities are written for kids in fourth through eight grades, but a teacher or parent could easily adapt all but two of the activities for younger students by working directly with the students rather than asking them to follow the written instructions.

Truly, kids of all ages will have fun with all the activities in this pack!