General Science and Teaching

Float/Sink for Younger Grades

Hello! I am teaching a lesson on float/sink for my first grade class. I know that my students don't need to be able to explain why an object floats or sinks but I'm not sure how in depth I need to go. Should I stop at "this floats, this sinks" and show them the objects in a tub of water or should I go farther and try to explain because it is lighter/heavier than water?

Thanks All!

Joy Annell Cross
Joy Annell Cross
540 Activity Points

Hi Joy! 

I am a student at the University of Northern Iowa, something we discuss in a lot of our classes is explaining the "why" to students.  I think it is important to explain to students why things sink or float, but that is something that you can simplify.  I would suggest refrain from using the phrase "more dense" or "less dense" I think students are going to grasp a better understanding of why things sink and float if they are given a little more information rather than "because I said."  Giving students something to think about can allow them to create their own educated guess of future objects.  For instance, you can give examples of objects which float and which sink and give an explaination (something simple) After, choose another object and allow them to choose if it would sink or float!

Jade Selig
Jade Selig
2155 Activity Points

Great question! Try and search for lessons that address this. What does your standard say about addressing floating or sinking? 

Pamela Dupre
Pamela Dupre
89534 Activity Points

I personally think its okay to just stop at showing them that it floats or sinks.

Teague Ross
Teague Ross
10 Activity Points

I agree that density is a difficult concept for young children to understand, or even for adults to explain to ourselves, and it is not necessary to explain it in a beginning exploration of why objects float or sink. In addition to the relative density of the objects, the shape also plays a part in whether or not an object floats. Multiple experiences over time--days and weeks and months--will help children develop their ideas about what makes an object sink or float. 

One misconception that people often hold is that heavy objects will sink. Involve children in comparing the weight of objects, either in their hands or using a balance. Choose objects that are small and lightweight but sink (small coin or stone) and some that are larger and heavier (orange or pumpkin) for children to compare and test for float-ability. Have them try two objects made of the same material but of different sizes--a small and a large block of wood. Test the objects yourself first! Each time they test an object, have children talk about the attributes of the object beforehand, including color, shape, size, weight, texture, and material. This will help them see that some attributes, such as color, are not related to whether or not the object floats.

Best wishes,


Peggy Ashbrook
Margaret Ashbrook
8085 Activity Points

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