Sunday, February 6, 2011

Science Sunday – Float or Sink

I found this fun book full of science experiments at a local thrift store:imageAll of the ideas in this book are perfect for the pre-k to 2nd grade crowd (in my opinion), and there’s a lot of cool extension activities for the child that may want a bit more.  All of the experiments are quick and easy to do; there’s a list of what you need, and most of the time it’s stuff you already have in your home.  We are really enjoying making our way through this book! 

We’ve done the basic sink or float experiment many times since M was a very little guy and just loved playing in the kitchen sink (mostly making a mess and blessing me with the opportunity to develop my patience).  This time we made it a bit more scientific by making predictions and sorting our items out in a variety of ways.

We used a divided tray with black squares of paper taped to the bottom (it’s a Christmas tray), and M began by writing an “F” for float on one side, and “S” for sink on the other side.Our sorting tray

S for Sink, F for Float

We went through the house gathering items into a basket, making sure to include things made of wood, metal, paper, or plastic, with a couple of other things thrown in too (like a tangerine, which we’ll get to later).  Then M made a prediction about each item and sorted them into his tray based on whether he thought they would float or sink:stuff to test I’m guessing he really just made random predictions; there didn’t seem to be any sort of consistency! ;)

We tried the “floaters” first, and he was right about most of them:floaters? 

Then we added in the “sinkers” and were surprised by quite a few things in this group actually floating, like the glass jar, and the large plastic block:testing all the items

Funny thing about the jar – it floated when it was empty, but sunk when we filled it up with water! 

A similar thing happened to a folded paper towel – it floated at first, but as it got wet it sunk.

AND – some things that sink will float if they are placed on top of a large floater!

We re-organized our sorting tray so each thing was on the correct side:re-sorted into the tray, correctly

Then we sorted them out into another tray according to what kind of material they were made from.  We realized anything that was metal sank.  Most of the heavy or large things sunk, unless they were filled with air; filled with air, these same things floated. We also realized that the things made from wood all floated.  A foam dart and a sponge floated too (until we squeezed all the air out of it under the water), as did most of the plastic items, except for the heavy car, which also had metal on it.

Our “floater” tray, separated by material:floaters, sorted by material

See the tangerine peel?  It has air pockets in it, which make the tangerine float.  We peeled it, and the peeling floated, but the fruit sank:tangerine peel floats, fruit sinks

And then he played:just playing   

I think M really already knew most of what we learned in this experiment, but being more orderly about “discovering” these things really made it stick in his mind.  He had so much fun with this, and his playing at the sink warmed this mama’s heart with memories, and also made me thankful that he is not nearly as messy anymore! :)

Have a beautiful day! :)


  1. oo how fun! I will definitely need to do this experiment soon!

  2. You know, I have never done a formal sink/float test with my daughter. But she does experiment in thje tub/pool etc.

  3. That book looks like an awesome find. Lots of great experiments to do.

  4. I love all of the different steps you used to do this.

    And the explanation for the tangerine, awesome!


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