Does Soap Float?

An inquiry based science lesson. Students use the Scientific Method to determine whether different brands of soap (including Ivory) will float.

• Students will apply the steps of the Scientific Method: Hypothesizing, experimenting, and concluding, to answer questions about the properties of soap. 

• Formulate relevant questions about the properties of objects, organisms, and events of the environment using observations and prior knowledge. 
• Predict the results of an investigation based on observed patterns, not random guessing. 
• Construct reasonable interpretations of the collected data based on formulated questions. 
• Compare the results of the investigation to predictions made prior to the investigation. 

Anticipatory Set- Have students start to think about whether soap floats.  What are some things you know that float if you put them in water? Some that sink?  In general, what do you think makes something float?  Do you think an empty paper cup would float?  Why or why not?  Do you think any of these four brands of soap will float?  Why? Today we are going to use the Scientific Method (Write these steps on the board: Hypothesizing, experimenting, and forming a conclusion) to find out whether these different soaps will float and why. 

Present New Material-

• 1. Input: Who remembers what a hypothesis is? Write hypothesis on the board. Make sure students know that a hypothesis is an educated guess that can be tested; a guess about what happens and why it happens before performing an experiment to prove or disprove it. A hypothesis is a proposition or a theory that explains something. Tell students to look at the three different bars of soap at their station. Do you think any of the three brands of soap will float? Why or why not? Explain that their answers to these questions will form a hypothesis that they will be testing with an experiment. Hand out the first Does Soap Float? student sheet. Tell students that they will write their hypothesis for each bar of soap on the sheet.
• 2. Modeling: My hypothesis for the first bar of soap is that it will not float because it is too heavy, so on my sheet, where it says Bar 1, in the box for hypothesis, I'm going to write: Bar 1 will sink because it is too heavy (demonstrate on the board). Next, I'm going to test my hypothesis by putting bar 1 in the bowl of water. Put bar 1 in bowl of water. It sank, so my hypothesis was correct! In the box labeled Observations, I am going to write: Bar 1 sank. You will do the same thing with bars 2, 3, and Ivory. Study the characteristics of each bar of soap. Write your hypothesis by answering these questions: Will this bar of soap float or sink? Why do you think so? After you write your hypothesis, test each bar of soap, and then record your observations.
• 3. Checking for understanding: Does everyone understand the directions? Randomly call on students to answer these questions: What is a hypothesis? What do you do before you drop the bar of soap in the water? After? Do you do one bar of soap at a time or all together?

Guided Practice-

Students write their hypotheses, do the experiment, and write their observations for each bar of soap.  As you walk around observing different groups, ask questions such as: What characteristics of the soap do you think determine whether it will float?  Do you think texture of the soap affects whether it will float?

After completion, ask students: Was your hypothesis correct for each of the soaps?  Did the Bars 2 or 3 float?  Students should have noticed that only the Ivory soap floated.  Discuss why they think that was.  Why do you think Ivory soap floated while the other brands didn't?  How is the appearance (size, texture, etc.) of Ivory soap different from the others?  Do you think that has something to do with why it floats? 

Based on what you learned about why Ivory soap floats, what do you think we could do to make the other brands of soap float?  What would happen if we heated or cooled the soaps?  How could we do this?  Lead students to the idea of heating soap in the microwave.  Distribute soap that has been heated in the microwave for 1 minute and allowed to cool. Tell students to study the new characteristics of the soap after it was heated.  What do they notice?  (Soap should be like "marshmallow fluff" and feel hard and stiff like Styrofoam.)  Have students predict whether the heated soap will float and record their hypothesis on Part II of the Does Soap Float? student sheet.  Have students place soap in bowl of water and record their observations.  

Independent practice-

Now have students read about the background of Ivory soap.  Have them read Pure Fun: Ivory Floating Soap Legend.   Have groups choose one of the following questions to discuss and answer on a small poster board. 

• Describe how Ivory soap's most famous feature-its ability to float-came about.
• Do you think the fact that Ivory soap floated had anything to do with its physical characteristics such as color and odor?  (Students should realize that it had nothing to do with things such as color and odor, but that it had to do with the air bubbles.) 
• What about Ivory soap makes it float? Lead them to the idea that air bubbles are the cause (the bubbles make the Ivory less dense than water). 
• What other objects float?  A sponge?  A Styrofoam cup?  A brick?  Why do you think these objects float? 
• Why did the soap float after it was heated? How is the heated soap more like Ivory soap?  

Have each student write a journal entry about the basic ideas they learned and what they thought of the experiment. 

Closure- Each group shares their board with question and answer displayed.  Discuss answers.  Post boards on a designated wall. 

• 3 bars of different brands of soap, one of each for each group (include Ivory soap)
• Bowl of water
• Paper plates
• Paper towels
• Does Soap Float? Student Sheet
• Pure Fun: Ivory Floating Soap Legend

Formal:  Collectively: presentation of each group.  Individually: journal entry of experiment.

Informal: Observation of students participating, discussion of the guiding questions