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DOES IT SINK OR FLOAT
MASTER TEACHER Maxine Haywood
GRADES 3 - 4
OVERVIEW
This lesson helps students understand the force of buoyancy,
displacement and how the density of an object affects these. Students will
predict buoyancy, affect the ability of a object to sink or float by changing
its shape and redesign an object's shape to hold more weight. Through
hands-on activities, students will discover that when the weight of an object is
distributed over the surface of the water, the object will float and when enough
force is placed on the water by an object it will break the surface tension and
sink.
ETV SERIES
Bill Nye the Science Guy #119 Buoyancy
Science Aboard Ship #102 Why Do Ships Float?
LEARNING OBJECTIVES
Students will be able to
* predict and observe the buoyancy of objects
* design a boat that will float
* redesign a boat that sank to enable it to float again.
* experiment with how the density of an object affects its
buoyancy
* experiment with how the density of water affects buoyancy
MATERIALS
per student
handouts
per group of 4
Experiment #1
recording sheets
objects to test buoyancy (ex. Cork, pencil, nail, wood, coin,
cotton ball, pen, plastic figure, etc.)
Experiment #2
Dish pan or bowl
Water to fill container 3/4 full
50 pennies
2 boxes of paper clips
1 bag of marbles
20 sticks of modeling clay
1 roll of paper towels
2 sheets of waxed paper to cover students work area
Experiment #3
1 Bowl or dish pan
Water to fill 3/4 full
1 orange
Experiment #4
1 wide mouthed glass
water to fill 3/4 full
1 container of salt
1 tablespoon
1 egg
VOCABULARY
sink - to go below the surface of a liquid partially or
completely
float - to rest on or at the surface of a liquid
density - the ratio of the mass of a substance to its
volume (density=mass/volume)
surface tension - force existing on any boundary
buoyancy - force that supports things in a liquid or gas
PREVIEWING ACTIVITIES
Begin the lesson by completing a KWL Chart on buoyancy. On
the KWL Chart you list under the K, information the students already know
about buoyancy, under the W, what students want to know, and at the end of the
lesson or unit list under the L, what has been learned.
Divide students into groups of 4. Provide them with a
variety of objects. Have them predict whether the objects will float
(positive buoyancy) or sink (negative buoyancy)and then to test their
hypothesis. Have them record their predictions and observations on a chart.
(Hand out at the end of this lesson) After the students have experimented,
ask students to list all the things that floated. What was similar about
them? Brainstorm answers. Have students list all items that sank.
What was similar about them? Brainstorm all answers. Have students
compare their responses and come up with a list of differences between objects
that floated and objects that sank.
Using the information students have come up with, say,
"Look at the objects that sank. Can you think of any way to modify
them so they will float?" Discuss. You might have your students
modify objects to see if they can make them float.
Experiment #1 Roll a stick of modeling clay into
a ball. Ask students to predict whether the clay ball will float or sink.
Observe and record what happens when the clay is placed in the water. ( the clay
will sink) Use the "How Do Boats Float" handout and the
scientific method recording sheet.
Experiment #2 Have students reassemble into groups.
Using the same size piece of clay used in experiment #1, have students design a
boat. Predict whether the clay boat will sink or float. Test the
boat to see if it will float. Now tell students they will add objects
(marbles, paper clips, pennies) to the boat. Have them predict how many
marbles they think the boat will hold before it sinks? Have students test
their hypothesises and record the number of objects the boat held.
Students can then redesign their boats to hold more items before sinking.
Have them analyze and conclude.
FOCUS FOR VIEWING
List the vocabulary words on the board. Have the students
record them on notepaper. To give the viewers a specific responsibility for
viewing say, "Now you're going to see a video on buoyancy. As you watch
listen for the definitions of the vocabulary words displacement and
buoyancy."
VIEWING ACTIVITIES
Begin the video after the voice says, "From viewers
like you." The visual is the National Science Foundation logo. Pause
when Bill Nye says, "Displace, place away. Are you with me?"
On the screen Bill is talking and the word displace is at the bottom of the
screen. Ask students what is the definition of displacement?
(Place away. When an object is placed in water, it pushes away an equal
volume of water.) Tell students to write down their definition. Resume
the video. Pause the video when a voice says, "Science
rules!" The visual is a fish floating across the screen. Ask what is
the reason an object sinks or floats? (An object placed in water pushes an equal
amount of water out of the way. An object that floats displaces an amount
of water equal to the weight of the object. Remember to tell
your students that the object's shape greatly influences its ability to float.)
What part if any, did buoyancy play when Bill Nye was in his boat on the
water?" (The object pushed away an amount of water equal to the
volume of the boat and its contents.) Resume the video. Pause
the video when the young boy in a blue lab coat says, "That's buoyancy,
that's science, that's cool." Ask students, "What caused
the clay boat to float?" (The clay boat and ball displace the same
amount of water but the shape of the clay boat makes the difference allowing it
to float.) Does the same hold true of the foil boat? (Yes)
What does buoyancy mean? ( The force that supports things in a liquid or
gas.) Have the students write the definition. Resume the
video. Stop the video when Bill jumps in the water. Say,
"Bill put on a personal floatation device. How does this device hold
us up in the water?" (Because we are mostly water, the device only
has to holdup that part of us that is not in the water.)
POST VIEWING ACTIVITIES
Say, "Now that we've learned some more about buoyancy lets
complete the L section of the KWL Chart listing what we have
learned." List what students have learned. Review and see if
the questions that were in the W section, listing what students wanted to know,
have been answered. Go over the vocabulary words and check that students
have the correct definitions. There are several words that were not
defined during the video and you will need to see if the students can define the
words or give them the definitions.
Experiment #3 Reassemble students in groups of 4. They will
use the dish pan or large bowl of water that was used in experiment #2.
Give each group an orange. Have them predict whether it will float.
Have students place an orange in the container of water. What happens?
(It floats) Now peel the orange. Ask students if the orange will still
float. Put it back in the water and watch what happens. (It will sink) Ask
students to hypothesize why this occurs. (The orange peel is full of trapped air
bubbles. This makes the orange light for its size, so it floats.
Without its peel and the air bubbles inside it, the orange weighs a lot for its
size. The peeled orange is more dense than water, so it sinks.)
Experiment #4 Give each group a large mouthed glass
filled mostly full of water. Give each group an egg and have them predict
if the egg will sink or float. Then have students gently lower the egg
into the glass of water. Say, "What happened? Why do you think it
happened" ( It will sink because the egg is more dense than water.)
Retrieve the egg. Have students pour ten tablespoons of salt into the
water, and stir until it all dissolves. This salt and water solution is
called brine. Ask students whether they think the egg will sink or float
now. Put the egg in the brine. Ask, What happened? Why do you
think it happened?" (Now it should float, because the salt has made the
water more dense that the egg. In the pervious experiments the density of
objects were changed to make them float or sink. With this
experiment you make an egg float by changing the density of the water, not the
egg.)
ACTION PLAN
Have a boat builder come to the class to talk about how buoyancy
affects the design of a ship.
Have students write The National Aeronautics and Space
Administration (NASA) requesting information on the treatment of waste water and
implementation of space technology in solving waste water and water reuse
problems.
EXTENSIONS
Language Arts
Have students brainstorm water words (ex. Rain, pond, gurgle,
ice, etc.) Have them then categorize the words into groups such as bodies
of water, forms of water, how water sounds, how water feels, etc. Have
students research why the Titanic sank. It was reported to be unsinkable.
Have them make a report, write a story about being on the ship as it sank, or
demonstrate why it sank.
Math
Give students problems that use buoyancy. If a ship
weights 24,553 lbs, takes on 12 tons of cargo, carries a crew of 42 people
weighting on the average of 182 lbs., what would be the weight of the water
would the ship displace? What if the ship stopped at the next port and
took on 42 tons of wheat and took on food weighting 4,532 lbs, and unloaded ½
of the cargo it had previous to its stop, what would the boat weight? Have
students make up problems.
Have students imagine that they live in a country where most
homes do not have running water. They must get water from the town well.
They need 3 gallons for breakfast, 4 gallons for lunch, and 5 gallons for
supper. Have them figure out how many trips they'll have to make to the
well and back for a day's water if they use only a one gallon jug, a 2 gallon
jug, etc. They have broken their jug and only have two 1 quart jars.
Now how many trips will they need to make. How many trips will they make
in one week, one month, etc.
Social Studies
Help students learn about ways their community stores and uses
water. Ask students to suggest places in the community that use water.
Talk about how they use water. Can they think of ways to conserve water.
Concluded by discussing dams, reservoir systems, water storage tanks, and
natural resources. Invite a speaker from the city water department
to talk with the students about how the city ensure the water supply and what
measure the community needs to take to conserve water.
Internet
Science Center for Educator Development www.tenet.edu/teks/science/index.html
Science Aboard Ship www.kedt.pbs.org
www.sasked.gov.sk.ca/doc/physics/u6d3phy.html
HANDOUTS
My Prediction Object Sink
Float Notes
__________________________________________
__________________________________________
Name_______________
What We Know
__________________________________________
What We Want to Find Out
__________________________________________
What We Learned
__________________________________________
How Do Boats Float?
Procedure
1. Roll clay into a ball. What happens when you
place the ball of clay in the water?____________
_______________________________________
2. Form the clay into a boat shape.
3. Draw a picture of your boat.
4. Predict what you think will happen if you add an
object to your boat. (Objects can be marbles, paper clips, coins,
etc.)_____________________
_______________________________________
5. Test your prediction by adding the objects to your boat
one by one. Continue until your boat sinks.
6. record the number of objects your boat held before it
sank.___________________________
7. redesign your boat to hold more marbles before sinking
and then repeat the experiment.
8. Analyze and conclude.___________________
________________________________________
________________________________________
Science Experiment Form
Name(s)_________________________________
Title of Experiment ________________________
Question What do we want to
find out?
_____________________________
_____________________________
Hypothesis What do we think we will find
out?
_____________________________
_____________________________
Procedure How will we find out? (List
steps)
1._____________________________
_____________________________
2._____________________________
_____________________________
3._____________________________
_____________________________
Results What
actually happened?
_____________________________
_____________________________
Conclusions What did we learn?
____________________________
____________________________
_____________________________
Updated: April 01, 2008
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