Science Lesson Plans
Posted May 24, 2016 by Elmers
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    Sink or Float?

    Students will observe different soda cans placed in water and predict why some sink and some float. This is a great discrepant event to use to introduce science fair.
    • 2 - 5
    • 1 hr
    • Science

    How do I get my class and myself ready? This lesson plan should give you everything you need to be prepared for the material.

    Lesson Plan Objective(s)

    Students will identify the variables in a scientific demonstration. 

    Students will understand that soda cans will either sink or float depending upon the density of the liquid (the amount of sugar in the drink).

    Background Details

    Discrepant events are ideal to use to teach the inquiry process. Why does something happen? How can we prove or disprove our theories as to why the cans float or sink?

    Materials Needed

    • Large tub of water
    • 6 cans of soda including regular, diet, sugar-free, and sparkling water 
    • Sharpie Marker
    • Aluminum foil

    Required Knowledge/Vocabulary

    density, buoyancy, sink, float

    How do I present the material? Here is the recommended approach, content and timing for presenting the materials.

    Lesson Instructions

    Prepare the lesson by wrapping a variety of cans of soda (i.e., diet soda, sparkling water, regular soda) in aluminum foil.  Use a Sharpie marker to identify each can with a letter or number.  Make a note of the contents of each, but do not disclose to the students which cans are diet, regular, or sparkling water. 

    Introduce the lesson by showing students the tub of water and holding up a regular can of soda. Ask them if they think the can will sink or float. Drop the can gently into the water and students will observe that the can will sink. Repeat the demonstration with another can of regular soda. 

    Ask the students if they think that all of the cans will float. Encourage them to provide their theories as to why or why not. 

    Repeat the demonstration with the rest of the soda cans. Students will observe that the some float and others sink. 

    Prompt them to make predictions about the contents of each can and why each sinks or floats.  Reveal the contents of the cans and provide time for students to determine why some sink while others float.

    Whether a can sinks or floats depends upon the density of the drink. The density is impacted by the amount of sugar or high-fructose corn syrup in the drink.

    Discussion Questions

    1. Do the cans weigh the same?
    2. Do they all contain the same amount of liquid?
    3. What could be different about the cans that would impact whether some sink and some float?
    4. How can you prove or disprove your theory?

    Activities (group or individual)

    Provide an opportunity for students to develop theories as to why some sink and some float. Then, let them test their theories.

    Did my students achieve the lesson objective?

    Activities (group or individual)

    Extend this lesson by changing the variable.  Make a sugar solution by dissolving sugar in warm water.  Use enough sugar to change the density of the water.  Fill one glass with the sugar solution.  Fill a second glass with tap water.  Fill a third glass with a mixture of the sugar solution and tap water.  (Note: Fill the third glass one half full with sugar water.  Slowly pour tap water down the side of the glass so that the tap water (less dense) floats on top of the sugar water (more dense).  

    Next, place a potato wedge in each glass.  The potato will float in the sugar water.  It will sink in the tap water. It will appear to be suspended in the third glass.  

    Students should be able to apply their understanding of density and how sugar impacts the density of a liquid to explain the different properties of each glass.


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