Sweet! Using Soda to Explore Density

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Students will further their understanding of density and buoyancy by completing an investigation.

Big Idea

Students are quickly drawn into this fun experiment comparing the difference between buoyancy and different types of soda.


10 minutes

We have completed several lessons that have given the students the opportunity to learn more about density. This lesson is another opportunity for students to apply their knowledge and understanding of density and experience a mini-nutrition lesson as well.

Materials needed:

  • An empty pop can
  • Large container with water  

To activate the students prior knowledge of buoyancy and density, I ask them some questions to set the stage for our learning based on some of our previous lessons.

What happened with the lemon and orange when we dropped it in the water with the peel on? 

What happened with the lime? 

What was the difference between the lemon and the lime?

Today, we are going to work with soda!  I have an empty pop can here.  I want you to talk at your table, what do you think will happen when I drop the empty can in the water?

I give the students time to discuss and have them share their predictions.  I then count off and we drop the can in the water.  After I drop the can, I ask them some more questions.

Why do you think the can floated?  What is inside the can?  What if the can had soda in it, what would happen?  Well, guess what?  That is what we are going to do today!





Investigation and Discussion Part 1

20 minutes

Materials Needed:

  • A large container to hold water for each work group

Materials Tip: I use plastic containers that held pretzels and animal crackers.  They are deep and allow a good view of the investigation (see photo)

  • Three cans of soda

Materials Tip: Two should be sugared sodas (one with a higher sugar content than the others and one that is diet--make sure to double check that the sugared ones sink and the diet one floats when dropped in water. 

  • Investigation recording sheet included as a pdf

The students are most likely going to come into this lesson with a misconception.  They will believe that anything that is heavy will sink.  This hands-on investigation will help disprove their misconception.  They will get they opportunity to see how an investigation can sometimes show how our ideas are not correct. 

Prior to the investigation, I fill the tubs with water and place them on each table. I pass out the recording sheet and have the students write their name at the top.  I say to the students, Today, we are going to conduct another investigation.  We are going to make some predictions about soda as to whether it sinks or floats.  We will begin with our first can of soda.  This is Can A (sugared soda, lower sugar content).  I want you to pass the can around the table and make a prediction as to whether you think it will sink or float.  Make sure to share WHY you are making that prediction.  Record you prediction on the recording sheet.  When every one is done, we will test to see if our prediction was correct.

The students pass the cans around and make predictions.  I visit with different students, asking them questions to help guide their predictions. (see video).  The students then count off and drop the soda can into the water (see video).  The students record their results. Overall, the majority of the students predicted the can would sink, so they were not surprised by the results of the first test.

I then pass around the can of diet soda.  I tell the the students that the diet soda is can B.  Again the students make predictions about the can.  The majority of the class says the can will sink.  They cite what happened with the other can as rationale for their prediction. 

Again, we hold the can of soda over the container of water.  We count down together and drop the can in the water.  The students are surprised to see the can floating. They record the results and then we have a conversation (see video)

I say to the students, Were you surprised by the results of our investigation?  Why do you think this can of pop floated when the other did not? 

At first they could not make a connection, so I reminded them that this soda was diet.  They started to formulate some ideas as to why the can floated, but the focused on the "fizz" in the soda instead of the lack of sugar.  I needed to remind them that diet soda does not contain sugar and from there, they were able to make the connection that the sugar in the soda increases its density.


Investigation and Discussion Part 2

15 minutes

To begin this part of the lesson, we watch a video that shows how much sugar is in a can of regular Coke.  The caption on the video may be a little over the heads of the students, but the visual of teaspoons of sugar is great!  The students count with me the spoonfuls of sugar.




After watching the video, the students really have an understanding about the amount of sugar that is in a can of soda.    I say to the students, Now, thinking about all that sugar, can you see why the density of the soda with sugar is higher than the diet soda?

The soda that we dropped in the water had 46 grams of sugar (adjust for the soda you used).  Now, we are going to test one more can of soda.  When I read the label, I see that it has 47 grams of sugar.  What do you think?  Will this soda sink or float?  Remember to use what you learned from the other cans of soda to make a good prediction. 

I have the students make their predictions.  After the students make their predictions and tell why, we again drop the can of soda in the water.  The students did a great job of applying what they learned to this part of the investigation.  I remind them, You were wonderful scientists!  I like how you used what you learned from other tests to figure out what would happen this time.  You were thinking like scientists!



5 minutes

To wrap up the lesson and to have the students make connections between today's lesson and prior learning during our nutrition unit, I pose the following question for discussion:  What do you think; after seeing all the sugar in that soda, what would be a good choice to drink when you are thirsty? 

I have the students discuss this question with their table group.  I then invite them to share their thoughts in the larger group.