BUOYANCY OR WHAT FLOATS YOUR BOAT
Grades 5 - 8

In this lesson, students will learn as Bill Nye the Science Guy discovers buoyancy. In this episode Bill Nye explores buoyancy through cars that are boats, real and toy boats, personal flotation devices, SCUBA, and human powered submarines. Students will observe two teacher demonstrations of buoyancy and perform two hands-on activities that (1) when objects like boats are placed in water they displace some of the water, (2) if an object placed in water weighs the same or less than the amount of water it displaces it will float, and (3) buoyancy also is responsible for allowing helium and hot air balloons to float.

Bill Nye the Science Guy: Discovers Buoyancy

Students will be able to:

• determine the volume of water displaced by an object placed in water.
• determine the mass of water displaced by an object placed in water.
• identify that when the mass of water displaced is equal to or greater than the mass of the object, the object will float.
• describe the rise of a hot air balloon in terms of molecular spacing and motion.
• determine the buoyancy of different objects in water.
• design a boat that will carry cargo.
• compare various boat shapes to cargo- carrying capacity.

"Coke Float" (Teacher Demonstration):

• one can Diet Coke
• one can regular Coke
• one two gallon transparent container of water

For each student:

• 1 Telecast Assessment Sheet (provided in Addendum)

"Pen Top Submarines" (Per student group of 2-4):

• one pen top
• one two liter bottle with cap
• marble-size ball of modeling clay
• water

"Hot Air Balloon" (Teacher demonstration):

• one plastic dry cleaning bag
• one electric hair dryer
• transparent tape

"What Floats Your Boat" (Per student group of 2-4):

• 1 Buoyancy Homework Sheet FOR EACH STUDENT
• 1 "What Floats Your Boat" directions sheet (provided in Addendum)
• 1 set of "What Floats Your Boat" data sheets (provided in Addendum)
• one stick of modeling clay
• one container at least 500 ml capacity
• small masses such as washers, BB's, pennies, pinto beans, gram cubes
• one balance
• water

The teacher will set up a demonstration that is designed to pique student curiosity. Use an aquarium, or any transparent container, that will hold at least two gallons. Fill it two-thirds full with water. As class begins pass out the Telecast Assessment Sheet and tell students, "Today I am going to show you an amazing sight. I have here two identically sized cans of soft drink made by the same company. One is a diet drink and one is a regular drink. What do you think will happen when I place each of them in this container of water?" Allow time for students to respond.

Write their hypotheses on the board.

Teacher: "Now, observe carefully as I place each one in the water. What is happening?" Write their observations on the board beside the hypotheses.

Teacher: "I would like for you to keep these hypotheses and observations in mind and answer the PRE-VIDEO question on your Telecast Assessment Sheet. We will return to our "Coke Float" after several days and see if we can determine what may be responsible for our observations."

Each student will have a Telecast Assessment Sheet (TAS). The teacher will go over the remaining questions/activities on the Telecast Assessment Sheet. Begin the TAS review with "Be sure that you have answered the PRE-VIDEO section of your Telecast Assessment Sheet. As we watch "Bill Nye, The Science Guy, Buoyancy" we will stop and do the INTERACTIVE section. After the video we will answer the POST-VIDEO section." Go over all the question on the TAS.

Day 1: Start the video from the beginning, after the opening credits.

PAUSE when Bill pours the water back into the boat mold.


Review with students that when an object like the boat is placed in water it pushes the water out of the way.

RESUME.

PAUSE when Bill puts the water and the boat on the balance. Review with students that the mass of water displaced balances the mass of the boat.

RESUME.

PAUSE after the segment demonstrating the effect of shape on floating. Review with students that shape makes a difference in floating and sinking.

RESUME.

PAUSE after the segment demonstrating a personal flotation device (PFD). Discuss the question on the TAS concerning the buoyant force stated on a PFD and allow students to arrive at the answer.

RESUME.

PAUSE after the "Try this" segment with the "Pen Top Submarine." Have students do the "Try this Pen Top Submarine" and answer the TAS question. End of Day 1. (If time becomes a problem the "Try this" segment could be done at the beginning of Day 2.) Collect the TAS.

Day 2: Return the TAS from Day 1. The teacher should conduct a brief review of the previous day's lesson. If the "Try this Pen Top Submarine" was not conducted on Day 1 do it now.

RESUME the video.

PAUSE after the segment where a "Hot Air Balloon" is demonstrated. Do the teacher demonstration of the plastic bag "Hot Air Balloon."

RESUME and play through to the end.

Have students answer the TAS. Hand out the Homework Sheet for "What Floats Your Boat." The Homework Sheet should be collected following the "What Floats Your Boat" activity.

Day 3-5. The teacher will introduce the activity by returning the scored Telecast Assessment Sheet and going over the answers to the TAS found on the "Answer Key" for the TAS. To complete this lesson return to the Coke Float hypotheses from the introduction.

Teacher: "Would you revise your hypothesis for the Coke Float based on the Bill Nye, The Science Guy, Buoyancy episode?" Allow students to elaborate on their answer to the question. Students may have suggested a number of reasons for the observation that the diet drink floats while the regular drink sinks. Among the usual suggestions are:

• one drink contains more caffeine than the other
• one drink contains more carbon dioxide than another
• one drink contains more volume than another
• sugar is heavier than sweetener

If the teacher doesn't wish to prolong the discussion and data collection she could read the content labels on the cans to the students:

• state that the cans contain the same total volume
• state that artificial sweeteners weigh much less than sugar in equal volumes and that the amount of sweetener used in diet drinks is much less in volume than the amount of sugar used in regular drinks.

Therefore diet drinks are less dense, more buoyant, than regular drinks. If the teacher desires, this activity can be extended for several days. The drinks could be weighed. The drinks could be opened and the volume determined. The drinks could be allowed to "go flat" to see if carbonation was a cause.

Students could mass an equal volume of sweetener and sugar to compare mass per volume.

Students could determine the density of each drink.

Follow the Coke Float discussion with the "What Floats Your Boat" activity.

Teacher: "Now, we are going to perform an investigation that examines the concepts presented in the "Bill Nye, The Science Guy, Buoyancy" video. Determine the size of student group you will use. This activity will work well with student teams of four.

Pass out the directions and Data Sheet for the activity.

Teacher: "Let's begin by reading over the directions for the activity." Read the activity sheet with the students. Assign duties to members of each team: -primary investigator -materials specialist -data specialist -quality control specialist

Indicate the location where students are to pick up and return the materials needed. Emphasize that students should pat dry the modeling clay with paper towels and reshape it into a ball before returning it.

Set up a Class Data Table on the board or on an acetate for the overhead projector. Students conduct "What Floats Your Boat" and report their results on the Class Data Table and by completing the Activity Sheet. This activity should take approximately 45-60 minutes to complete. If it is necessary to break it up into two class periods have students collect the data one day and analyze it to complete the Data Sheet the next. At the end of class remind students that the Homework Sheet is to be returned the following day.

On the following day the teacher will go over the class results from "What Floats Your Boat." Discuss the designs that were most successful. Be sure to allow students to provide their reasons for the designs that were most successful. Be sure to allow students to provide their reasons for the design's success. Collect the Student Data Sheets for each group.

Teacher: "Students take out your Homework Sheets. Exchange them with other students on your team. Read over them in your group, then we will have one member of each team report to the class on what your team discovered." After team discussion one member of each team should give a summary report of their results from the Homework Sheet.

An "Examples of Buoyancy" bulletin board could be maintained in the classroom throughout the remainder of the school year. A SCUBA diver could be invited to show students her gear and tell how the concept of buoyancy is used in diving.

• Students could build and fly tissue paper of hot air balloons. Directions are included.
• Students could learn and present the "Bill's Got A Boat" rap. Text included.
• Students could develop a mini buoyancy lesson to present to students in a lower grade.

---

Bill Nye, The Science Guy, Buoyancy "What Floats Your Boat" Activity Directions

Pick up the materials your group will need.

• modeling clay
• clear plastic container (the bottom part of a two liter bottle)
• tape
• metric ruler
• balance
• masses

Put a strip of tape on the outside of the container from top to bottom. This will be where you mark the changes in water level.

Determine the mass of one of the objects you will use t o add weight to your boat. Record this mass in the data table.

Fill the container two-thirds full of water. Make a mark on the tape strip on the outside at the water level.

Make a ball of the modeling clay. Determine the mass of the clay ball. Record the mass of the clay in the data table.

Drop it into the water. Mark the new water level on the tape. Use the ruler to measure the change in water level. Record the water level change in the data table.

Remove the clay ball. Brainstorm with your team to design a shape from the clay that you think will float and hold the most weight. Sketch the shape. Reshape the clay. Be sure to use the same amount of clay. Put your new clay boat in the water. Mark the water level. Measure the change and record.

Predict how many pieces of cargo your boat will hold. Record your prediction in the data table.

Test your prediction by adding cargo pieces to your boat. Each time you add a piece mark the change in water level on the tape strip. Measure and record the change in water level. Add cargo pieces until the boat sinks. Pat dry your clay and weights. Return the materials.

Send one member of your team to record how many pieces of cargo your boat held on the class data table on the board.

Graph the data you have recorded.

Answer the questions about the activity.

---

Master Teacher: Mary Alice Fryar
WJCT