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[KIDS] Vocabulary Word of the Week: Density

The word of the week is density. Density shows how tightly or closely atoms are packed together. The closer the atoms are, the denser the material. Density is one of the reasons why something will float or sink in water. In this experiment, you’ll predict whether an object will float in water. This means you’ll make an educated guess. Then you’ll learn what density has to do with floating in water.


  1. Paper and pencil

  2. Clear, deep bowl or cup filled with water

  3. Different household objects (ie. cork, rock, paperclip)


  1. Gather the materials you are going to use from around your house. Make a list of all of the objects. Write if you think they are going to float or sink next to each item. This is your hypothesis.

  2. To test your hypothesis, drop the first object in the bowl. See if it floats or if it sinks. Make sure to take note of whether or not the object actually sinks or floats. Once you’ve tested the first material, remove it from the water and drop you second object in. Continue this process until all of the items have been tested.

  3. Now, look at your hypotheses and compare it to what actually happened. If you weren’t right for all of them, that’s okay, the important part of this experiment was learning about density! Based on what you observed, why do you think some things floated and some didn’t?

The Science of Sinking:

All of the materials around us have different densities. For example, the density of water is 1000 kg/m3, if the density of another object is less than that it will float, and if it’s more, it will sink. That’s exactly what you saw in this experiment! Is it surprising to you that solid objects are sometimes less dense than liquid? Do you think all liquids have the same density? Try adding oil to a clear glass of water. What do you notice about the liquids? How dense do you think they are?

By Maariyah Mustafa & Natalie Duerr

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