Sink vs. Float

Every year I like to do a sink vs. float activity with my students.  We begin by discussing what it means to sink and what it means to float.  We make some guesses as to why some things sink and some things float, and we give some examples of objects that we already know float, or sink.  We then read this book:

Floating and Sinking by Amy Hansen gives the students great information as to why some things float, and other do not.  It has great pictures, and I found it to be the perfect amount of explanation on the concept for kindergartens students.

After we read the book, we experiment with some objects in our classroom. I like to use objects  that can easily be found around the classroom so that it requires little prep for me, especially on those days that I have a lot on my plate #everyday.  I begin by collecting all of the materials, and fill a large plastic container with water.

I let the students come up one at a time and do the test.  Before we drop it in, we take some guesses as to whether it will sink or float, and support our guesses by referring back to information that we learned in the book we just read.

While we are testing out our materials, we are also simultaneously recording the information in our pocket chart.

When the experiment has concluded, we check our understanding by completing a sink vs float sorting activity.

The students take out their interactive journals, and add this activity into them.  The class always finds this activity engaging, and with all the tools organized ahead of time, it is a stress free way to get some hands on science into your classroom!  If you would like a copy of the sorting activity and cards, click on the link below:

If you are interested in more activities such as this one, check out my Kindergarten Interactive Science Journal that provides you with a year's worth of resources to support your science curriculum!


  1. I am doing a student teaching lesson next week on sink or float. However, I am worried about the questioning part of the lesson. How do you explain to kindergarteners why some things sink or float?

    1. Hi Natalie!
      I don't get too much into the mechanics of why things sink vs. float with kinder kids, but you can show them a YouTube video like this:

      Or grab a book from Amazon like this:

      I like to use either a video or a book before I begin the lesson so that my kids can get some extra visuals, and some good science talk from the professionals : )

      Good luck with your lesson! Let me know how it goes!