That's Fruity-Even More Explorations of Density

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Students will be able to use what they know about density to make and test predictions about whether kiwis and grapefruits float by conducting an investigation.

Big Idea

In previous lessons, the students have had the opportunity to test a variety of fruits to see if they sink or float. Can they apply the knowledge that they have gained to kiwis and grapefruits.


5 minutes

This lesson was not one that I actually planned on doing, but I had a student show up with a bag of grapefruit and kiwis and ask if we could test them out.  He had talked his mom into going shopping for them so we had more fruit to test!  Obviously, our previous lessons in which we tested the buoyancy of oranges, lemons and limes were inspiring for this child.  He was thinking about a scientific question outside of the classroom and convinced his mother to help us test this question.  He was thinking like a scientist!

I thought about it and, it occurred to me, "Wow...this is a great way to have the students really apply what they learned to make predictions about buoyancy." Hopefully, they will make connections between our different investigations.

Honestly, I did not know what would happen with each fruit.  I could have tested it, but I thought it would be more fun to really experience the investigation with the students and make my predictions with them.  

I begin the lesson by explaining to the students how this student posed a scientific question and new that he could find the answer for it by conducting an experiment.  I want to praise and support this behavior.


Investigation and Discussion

30 minutes

Materials Needed:

  • A large container for water
  • A grapefruit for each group of students
  • A kiwi for each group of students
  • Investigation recording sheet included as a PDF with this lesson

To begin the investigation, I pass out the recording sheet and have the students write their name on it.  I tell the students, We are going to make a prediction about whether this grapefruit will sink or float.  I want you to think about what we learned about the orange, the lemon, the lime and we are going to apply what we learned from our investigations with these fruits to the grapefruit and make a prediction about whether it will sink or float.  Pass the grapefruit around the group and make your prediction and tell why you think that will happen.  Make sure you record your prediction on your paper.

The students pass the grapefruit around the table and they make their predictions.  I ask questions to get them to verbalize the "why" of their prediction (see video).  I want them to make connections to our other investigations.

After everyone makes their prediction, the students hold the grapefruit over the container of water.  We count off as a group and the students drop the grapefruit (see video).  The students then record the results  We talk about what happened.  I guide the students to think about our other investigations by asking them some questions.

Now that you saw what happened, what fruit do you think the grapefruit is more like, the orange, the lemon or the lime?  Why do you think that?  We are going to peel to grapefruit and try dropping it again.  I want you to make a prediction and tell why you think your prediction is correct?

The students peel the grapefruit.  They then pass it around and make a prediction.  I again help them to share the WHY of their prediction in my conversations with them. 

After everyone has had the opportunity to make a prediction, we again count off and drop the peeled grapefruit into the water.  I ask the students a few more questions.

What happened?  Was your prediction correct?  What information did you use to make this prediction?  Do you think it helped you make a better prediction because the other three fruits did not float when peeled?  Why?

We then repeat the above process with the kiwi.




10 minutes

To wrap up our learning, I want to challenge my students to continue to think about how they can apply the knowledge they have gained from our investigations.  I have the students partner up with their Turn and Talk.  I use Turn and Talk often in my classroom.  It allows my English Language Learners the opportunity to practice their language skills and use vocabulary.  Since kindergarteners are all English Language Learners, this is valuable for all my students. 


I ask them to think of some other kind of fruit and to make a prediction as to whether the fruit will sink or float and why they think that.  I encourage them to use what they have learned during our different investigations.