Title: Buoyancy
Grade Level(s): 7,8
Subjects: Math and Science
Learner Outcomes:
Goal of Lesson:
The student will be able to relate the concepts of buoyancy
and weight to the forces that allow an object to float.
Objectives:
1. The student will predict and observe the behavior
of regular and diet soft drink
cans when immersed in
water.
2. The student will calculate the density of the
soda solutions by using
mass/volume data.
3. The student will relate density to neutral buoyancy.
Time Frame: 45 minute class period
Materials:
1. Group students in groups of four.
2. Small aquarium or other large, deep, straight-sided
container filled with
water for demonstration.
3. Per group:
a. one can of regular Coke; one can of Diet Coke
one can of regular 7-Up; one can of Diet 7-Up
b. one empty Coke can; one empty Diet Coke can
one empty regular 7-Up can; one empty Diet 7-Up can
4. Paper towels
5. Ice
6. Plastic foam (cups, blocks, Styrofoam packing
"peanuts")
7. Water resistant tape
8. Finishing nails or metal washers of several
sizes
9. Balances
Technology:
Use of computer and Internet access.
Teacher Notes:
Safety: No horseplay or splashing water.
*The brand names of soft drinks are recommended because
some other brands may
not exhibit any significant differences
between regular and diet versions.
*Before the activity, test several cans of soda to be
sure the desired results are obtained.
Cans can have slightly different volumes
that can affect buoyancy.
Preassessment:
Teacher notes:
1. Explain the concepts of buoyant
force and weight. Buoyant force acts upon an object
causing it to float.
2. An object will float when the buoyant force
is greater than its weight.
3. An object will sink when its weight is greater
than the buoyant
force.
4. Define neutrally buoyant: When the buoyant
force and weight
are equal, the object is neutrally
buoyant.
5. Explain than engineers must design machines
to be energy efficient.
When using a machine to explore
underwater, it is important for it to
be neutrally buoyant so it will
not have to expend energy to remain at a
constant depth. Submersibles
are neutrally buoyant.
Teacher Demonstration:
1. Show the students the unopened cans of the regular
and diet sodas.
2. Ask the students how they can tell the difference
between the two cans.
3. Summarize the responses on the board.
4. Have students predict what would happen if the
cans were placed in water.
5. Fully submerse cans of regular soda. (It
should sink and stay at the bottom).
6. Fully submerse cans of diet soda. (It should
rise to the surface and float).
7. Compare the student observations with their
predictions.
Student Exploration:
1. Hand out plastic foam, nails, and washers.
2. Use the balance to determine: mass of
an empty, dry, regular soda can
: mass of an empty, dry, diet soda can
: mass of full, unopened regular soda
: mass of full, unopened diet soda
: record all masses on data table.
3. Record the volume from the cans of both regular
and diet soda
and record on the data
table.
4. Record the information on the data table.
5. Calculate the density
of the unopened cans using the formula
D = M/V.
6. Let students experiment with modifications of
the cans by attaching the
foam, nails, and washers to
the cans of soda to make them hover, rise or float.
7. Have students place ice into the water and predict
whether buoyancy is
affected by the temperature
of the water. Have students experiment with ice
water and room temperature water
to determine if temperature affects buoyancy.
Modifications:
All students can participate in the group setting.
Enrichment Activities:
1. Use the Internet to find out how submersibles
and submarines work.
2. Use the Internet to find out about the sizes
of different whales.
Use graphing software to make
a graph comparing the different
sizes of whales.
Evaluation/Assessment