LESSON 4: Buoyant Butter
ESTIMATED TIME Setup: 5 minutes | Procedure: 5–10 minutes
• DESCRIPTION
• MATERIALS
Calculate the density of a stick of butter to
determine if it will sink or float in water.
Stick of butter or margarine (with the wrapper on)
Metric ruler
o Large bowl or container
o
o
• OBJECTIVE
This lesson teaches students about density, how to
calculate it, and how it is related to determining
whether an object will sink or float in a certain
liquid. Students will measure sticks of butter or
margarine to determine whether they will sink or float
in water. The lesson can be simplified to reinforce the
importance of measurement in a scientific experiment.
Always remember to use the appropriate safety
equipment when conducting your experiment.
Refer to the Safety First section in the Resource Guide
on pages 421–423 for more detailed information about
safety in the classroom.
Jump ahead to page 58 to view the
Experimental Procedure.
• CONTENT TOPICS
Scientific inquiry; measurement; properties of matter
(density)
NATIONAL SCIENCE EDUCATION STANDARDS SUBJECT MATTER
This lesson applies both Dimension 1: Scientific and Engineering Practices and Dimension 2: Crosscutting Concepts
from “A Framework for K–12 Science Education,” established as a guide for the updated National Science Education
Standards. In addition, this lesson covers the following Disciplinary Core Ideas from that framework:
• PS1.A: Structure and Properties of Matter
• PS2.A: Forces and Motion
• ETS2.A: Interdependence of Science, Engineering, and Technology (see Analysis & Conclusion)
• ETS2.B: Influence of Engineering, Technology, and Science on Society and the Natural World
(see Analysis & Conclusion)
OBSERVATION & RESEARCH
BACKGROUND
Mass and volume are common units of measure. Mass is
a measure of the amount of matter in a substance. (It’s the
amount of “stuff” in a substance.) Volume is the amount
of space an object occupies.
Density is an important concept in chemistry that is defined
as the mass of an object per unit volume. Density is a
physical property of matter that describes how closely
packed together the atoms or molecules of a substance are.
The formula used to calculate density is d = m/v, where
d is the density, m is the mass of the object, and v is the
volume of the object.
Scientists use density in different ways. They use it to
identify unknown substances and to separate different
liquids.
In this experiment, students determine the density of an
object and compare it to the density of water. The
approximate density of liquid water is 1.0 gram per
milliliter (g/mL). This means that one milliliter of water
will have a mass of one gram; thus, it will weigh one
gram on the earth. In general, a substance that is less
dense than water will rest on top of the water, and a
substance that is denser than water will sink. Therefore,
a copper coin, which has a density of 8.96 g/cm3 would
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LESSON 4: Buoyant Butter
sink in water. On the other hand, if we have a 10-gram
piece of wood with a volume of 20 milliliters, we would
first calculate the density of the wood. Using the
equation, we know that the density of the wood is
0.5 g/mL. Because this number is less than the density
of water (1.0 g/mL), the wood will float.
You can also determine whether the wood will float
using another method. Since we know the object weighs
10 grams and the volume is 20 milliliters, we can then
determine how much 20 milliliters of water weighs.
The answer (using the density equation) is 20 grams,
which is more than the piece of wood. Therefore, again,
we know that the wood will float.
Density, however, is not the only consideration. Think
about a ship made of steel. Although steel has a density
greater than water, the shape of the boat spreads the
weight of the steel over a larger space. In addition, some
of that space is filled with air, which is much less dense
than water. Therefore, whether an object sinks or floats
also has to do with displacement. Displacement occurs
when one substance takes the place of another. When an
object is placed in water, it will displace some of the
water. (Think about sitting in a bathtub. When you sit
down, the water will rise, as your body takes the place of
some of the water.) In general, if an object weighs more
than the water it displaces, the object will sink. If an
object weighs less than the water it displaces, it will
float. Buoyancy is the upward force that a fluid exerts on
an object that enables the object to float. The buoyant
force on an object is equal to the weight of the fluid
displaced by the object.
FORMULAS & EQUATIONS
Certain laboratory equipment can be used to gather
different measurements. The mass of an object can be
determined by using a balance. The volume of a liquid
can be easily determined by pouring the liquid into a
graduated cylinder. For solid objects, measuring volume
takes a little more effort. You can calculate the volume of
rectangular solids with the following equation:
CONNECT TO THE YOU BE THE
CHEMIST CHALLENGE
For additional background information, please
review CEF’s Challenge study materials online at
http://www.chemed.org/ybtc/challenge/study.aspx.
• Additional information on measurement and types
of physical measurements can be found in the
Measurement section of CEF’s Passport to
Science Exploration: The Core of Chemistry.
• Additional information on properties of matter
can be found in the Classification of Matter
section of CEF’s Passport to Science Exploration:
The Core of Chemistry.
• Additional information on displacement can be
found in the Laboratory Equipment section of
CEF’s Passport to Science Exploration: The Core
of Chemistry.
The volume of a solid is therefore measured in cubic
centimeters (or cubic meters). For solids with an irregular
shape, you can use a displacement method.
Once the mass and volume of an object have been
determined, the density of that object can be calculated.
Use the following equation: d = m/v.
Density is measured in grams per milliliter or grams per
cubic centimeters. One cubic centimeter (cm3 or cc) is
equal to one milliliter (mL).
HYPOTHESIS
uDensity can be calculated using the mass
and volume of an object. If the average
density of an object is less than the average
density of water, it will float.
v=l×w×h
where v is the volume, l is the length of the object, w is
the width of the object, and h is the height of the object.
You Be The Chemist® Activity Guide | page 56
LESSON 4: Buoyant Butter
DIFFERENTIATION IN THE CLASSROOM
LOWER GRADE LEVELS/BEGINNERS
DESCRIPTION
Practice performing different measurements to reinforce the
importance of measurement and explain the difference
between accuracy and precision. Students will calculate the
mass, volume, and density of different sized pieces of
butter.
OBJECTIVE
This lesson reinforces the importance of measurement
and allows students to practice measuring mass, volume,
and density.
OBSERVATION & RESEARCH
Measurement is perhaps one of the most fundamental
concepts in science. It is the process of determining the
ratio of a physical quantity, such as length or a mass, to a
unit of measurement. Without the ability to measure, it
would be difficult for scientists to conduct experiments or
form theories. Not only is measurement important in
science, but it is also essential in industry, farming,
engineering, construction, manufacturing, commerce, and
numerous other occupations and activities.
A good example of measurement is using a ruler to find the
length of an object. The object is whatever you are
measuring, the property you are trying to determine is the
object’s length, and the standard you are comparing the
object’s length to is the ruler.
Scientists have two goals when they take measurements.
They want their measurements to be accurate by getting as
close as possible to the true measurement of something.
They also want their measurements to be precise so that
they can take the same measurement and get the same
result over and over. You should strive to achieve accuracy
and precision in your measurements.
Measurement is never 100% accurate, so the true value of a
measurement is never exactly known. This uncertainty is a
result of error, a concept which is associated with
measuring, because measurement is always a comparison
to a standard. Manually measuring something always
involves uncertainty because it is based on judgment. If two
people use a ruler to measure how tall a plant is, it may
look like 20 cm to one person and 18 cm to the other.
To increase the accuracy of a measurement, therefore
reducing error, an object should always be measured more
than once. Taking multiple measurements and then
determining the average measurement increases the
likelihood that you have the exact measurement.
There are several properties of objects that scientists need
to measure, but the most useful and common properties are
length and mass. Length is a measure of how long an object
is, and mass is a measure of how much matter is in an
object. Mass and length are base units, meaning that they
are independent of all other units. Most units of measure,
such as volume and density, are derived or calculated from
base units.
For example, density is derived from the base measurement
units of mass and length. Density is an important concept in
chemistry, defined as the mass of an object per unit volume.
Density is a physical property of matter that describes how
closely packed together the atoms of an element or the
molecules of a compound are. The formula used to
calculate density is d = m/v, where d is the density, m is the
mass of the object, and v is the volume of the object.
CONNECT TO THE YOU BE THE
CHEMIST CHALLENGE
For additional background information, please
review CEF’s Challenge study materials online at
http://www.chemed.org/ybtc/challenge/study.aspx.
• Additional information on measurement can be
found in the Measurement section of CEF’s
Passport to Science Exploration: The Core of
Chemistry.
• Additional information on measuring mass and
volume can be found in the Laboratory Equipment
section of CEF’s Passport to Science Exploration:
The Core of Chemistry.
• Additional information on density can be found
in the Classification of Matter section of
CEF’s Passport to Science Exploration: The Core
of Chemistry.
You Be The Chemist® Activity Guide | page 57
LESSON 4: Buoyant Butter
DIFFERENTIATION IN THE CLASSROOM
HIGHER GRADE LEVELS/ADVANCED STUDENTS
Perform the experiment as described below, but explore
the concept of density further. Have students perform
different measurements and calculate the density of
various objects. Discuss density as it relates to solids,
liquids, and gases. Can liquids “float” on top of one
another? See the Modifications/Extensions section for
other ideas to reinforce the concept of density.
Another option is to discuss buoyancy in more detail, as
well as other forces, such as gravity, friction, and nuclear
forces. Explore the differences between those forces.
EXPERIMENTATION
As the students perform the experiment, challenge them to identify the independent, dependent, and controlled variables,
as well as whether there is a control setup for the experiment. (Hint: If you change the volume of the stick of butter, will it
act the same way in water?) Review the information in the Scientific Inquiry section on pages 14–16 to discuss variables.
3. Multiply length × width × height, and record that
EXPERIMENTAL PROCEDURE
Before the experiment, ask the students if
the stick of butter will float or sink in water.
Ask them if they know how to figure this out without
testing it in water.
number in cm3, which is equal to a milliliter (mL).
4. To determine the approximate density of your stick
of butter, divide the mass of the butter (in grams)
by its volume (in cm3).
1. Determine the mass of the butter or margarine in
the stick. This amount (in grams) is printed on the
wrapper of the butter. You can also weigh the
butter on a balance to find the mass.
2. To determine how much space the butter takes up
(volume), measure the length, width, and height
of the stick of butter in centimeters (cm).
DATA COLLECTION
Have students record data in their science notebooks
or on the following activity sheet. What are the
measurements for length, width, and height of the
stick of butter? What is the mass of the stick of butter?
You can use the table provided in the activity sheet
(or a similar one of your own) for students to record
their data.
5. Now compare your calculated density of the
butter to that of water (1 g/mL), and determine
whether the object will sink or float.
6. Fill the bowl or container with water, and place the
stick of butter in the water to observe what happens.
It is best to use a frozen stick of butter.
NOTES
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LESSON 4: Buoyant Butter
ANALYSIS & CONCLUSION
water. You can also discuss the differences between
salt water and freshwater. Ask them to think about
whether it is easier to float in the ocean or a
freshwater pool. Because salt water is denser than
freshwater, people can float much easier in the ocean.
Use the questions from the activity sheet or your own
questions to discuss the experimental data. Ask students
to determine whether they should accept or reject their
hypotheses. Review the information in the Scientific
Inquiry section on pages 14–16 to discuss valid and
invalid hypotheses.
• Explain the concept of density using a visual.
For example, use mini-marshmallows in a clear box
to show how mass can change in a given volume.
ASSESSMENT/GOALS
Upon completion of this lesson, students should be able
to …
• Apply a scientific inquiry process and perform an
experiment.
• Understand the importance of taking careful
measurements.
• Understand density, displacement, and buoyancy as
they relate to whether an object will sink or float in a
liquid.
• Explain the concept of density and calculate the density
of an object if given the mass and volume.
• Understand the importance of accuracy and precision to
measurement (see Differentiation in the Classroom).
K-4
See Lesson 12: Density Totem for another lesson
on density.
5-8
See Lesson 19: Liquid Rainbow for a more complex
density lesson.
REAL-WORLD APPLICATIONS
• Challenge the students by asking them how huge
boats made of metal can float. Then, explain that the
massive weight of the boat is spread out over a large
area. Thus it has a large volume, making it possible
to float in water.
• The concepts of density and buoyancy are vital to the
development of large ships, such as aircraft carriers,
cargo ships, and cruise ships.
COMMUNICATION
MODIFICATIONS/EXTENSIONS
Modifications and extensions provide alternative methods
for performing the lesson or similar lessons. They also
introduce ways to expand on the content topics presented
and think beyond those topics. Use the following
examples, or have a discussion to generate other ideas as
a class.
• Try using sticks of butter at different temperatures.
Ask the students if they think a frozen stick of butter
and a room-temperature stick of butter will act the
same when placed in water. Then, place each in water
to see what happens.
Discuss the results as a class and review the activity sheet.
Review the information in the Scientific Inquiry section on
pages 14–16 to discuss the importance of communication
to scientific progress.
Fun Fact
The Dead Sea, which is
located in the Middle East, has
a very high concentration of salt.
Its density is so great that
• Try different objects, and ask the students if the
objects will sink or float. Ask them what that means
about the density of the object in relation to the
anyone can float, almost lie,
You Be The Chemist® Activity Guide | page 59
in the water.
LESSON 4 ACTIVITY SHEET: Buoyant Butter
OBSERVE & RESEARCH
1. Write down the materials you observe. ________________________________________________________________
______________________________________________________________________________________________________
______________________________________________________________________________________________________
2. Predict how these materials may be used. ______________________________________________________________
______________________________________________________________________________________________________
______________________________________________________________________________________________________
3. Define the following key terms. Then, provide an example of each by writing the example or drawing/pasting an
image of the example.
Term
Definition
Example (write or add image)
Mass
Volume
Density
Displacement
4. Consider what will happen when the stick of butter is placed in water and why.
uWrite your hypothesis. ______________________________________________________________
______________________________________________________________________________________
______________________________________________________________________________________
You Be The Chemist® Activity Guide | page 60
LESSON 4 ACTIVITY SHEET: Buoyant Butter
PERFORM YOUR EXPERIMENT
1. Determine the mass of the stick of butter. This amount (in grams) is printed on the wrapper or can be found by
placing the stick of butter on a balance.
2. Measure the length, width, and height of the stick of butter in centimeters (cm) to determine the volume.
3. Multiply the length, width, and height (length × width × height). Record that number in cm3. This amount is
the volume.
4. Determine the approximate density of your stick of butter by dividing its mass by its volume.
1 cm3 = 1 mL. Use this formula to convert your units from g/cm3 to g/mL.
5. Compare your calculated density of the butter to the density of water (1 g/mL). Do you think the butter will sink
or float?
6. Fill the bowl with water, and place the stick of butter in the water. Observe what happens.
ANALYZE & CONCLUDE
1. Record your measurements and calculations in the following table.
Mass of Butter (g)
Length (cm)
Width (cm)
Height (cm)
Volume (cm3)
Density of Butter (g/cm3)
Density of Water (g/mL)
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LESSON 4 ACTIVITY SHEET: Buoyant Butter
2. What is the formula for density? What is the unit of measurement for density? ________________________________
______________________________________________________________________________________________________
______________________________________________________________________________________________________
3. Based on your calculation, is the density of the butter greater or less than the density of water? __________________
______________________________________________________________________________________________________
______________________________________________________________________________________________________
4. Do you think the butter will sink or float? Why? ________________________________________________________
______________________________________________________________________________________________________
______________________________________________________________________________________________________
5. If you place the stick of butter in salt water, do you think it will sink or float? Why?
__________________________
______________________________________________________________________________________________________
______________________________________________________________________________________________________
6. Is your hypothesis valid? Why or why not? If not, what would be your next steps? ____________________________
______________________________________________________________________________________________________
______________________________________________________________________________________________________
You Be The Chemist® Activity Guide | page 62
LESSON 4 ACTIVITY SHEET: Buoyant Butter
SHARE YOUR KNOWLEDGE
1. Define the following key terms. Then, provide an example of each by writing the example or drawing/pasting an
image of the example.
Term
Definition
Example (write or add image)
Measurement
Accuracy
Precision
2. List some objects that you think have a density greater than water.
________________________________________
______________________________________________________________________________________________________
______________________________________________________________________________________________________
3. List some objects that you think have a density less than water.
__________________________________________
______________________________________________________________________________________________________
______________________________________________________________________________________________________
4. If you cut the stick of butter in half, will its density change? Why or why not?
______________________________
______________________________________________________________________________________________________
______________________________________________________________________________________________________
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LESSON 4 ACTIVITY SHEET: Buoyant Butter
ANSWER KEY: Below are suggested answers. Other answers may also be acceptable.
OBSERVE & RESEARCH
Stick of butter/margarine, metric ruler, large bowl, water …
1. Write down the materials you observe. ________________________________________________________________
______________________________________________________________________________________________________
______________________________________________________________________________________________________
The butter may be used for cooking. The ruler may be used to take measurements.
2. Predict how these materials may be used. ______________________________________________________________
The bowl may be used to hold water or other materials. These materials may be used to identify and compare the physical properties of butter
______________________________________________________________________________________________________
and water.
______________________________________________________________________________________________________
3. Define the following key terms. Then, provide an example of each by writing the example or drawing/pasting an
image of the example.
Term
Definition
Mass
A measure of the amount of matter in a substance.
Volume
A physical property that measures the amount of
space a substance occupies.
Density
A physical property of matter that describes how
closely packed together the atoms of an element or
the molecules of a compound are; the amount of
matter per unit of volume (d = m/v).
Displacement
The act of moving something out of its original
position or of one substance taking the place of
another.
Example (write or add image)
4. Consider what will happen when the stick of butter is placed in water and why.
Density can be calculated using the mass and volume of an object. If an object is
uWrite your hypothesis. ______________________________________________________________
denser than the water it displaces, it will sink. If an object is less dense than the water it displaces, it will float.
______________________________________________________________________________________
______________________________________________________________________________________
You Be The Chemist® Activity Guide | page 64
LESSON 4 ACTIVITY SHEET: Buoyant Butter
ANSWER KEY: Below are suggested answers. Other answers may also be acceptable.
PERFORM YOUR EXPERIMENT
1. Determine the mass of the stick of butter. This amount (in grams) is printed on the wrapper or can be found by
placing the stick of butter on a balance.
2. Measure the length, width, and height of the stick of butter in centimeters (cm) to determine the volume.
3. Multiply the length, width, and height (length × width × height). Record that number in cm3. This amount is
the volume.
4. Determine the approximate density of your stick of butter by dividing its mass by its volume.
1 cm3 = 1 mL. Use this formula to convert your units from g/cm3 to g/mL.
5. Compare your calculated density of the butter to the density of water (1 g/mL). Do you think the butter will sink
or float?
6. Fill the bowl with water, and place the stick of butter in the water. Observe what happens.
ANALYZE & CONCLUDE
1. Record your measurements and calculations in the following table.
Mass of Butter (g)
Answers will vary
Length (cm)
Answers will vary
Width (cm)
Answers will vary
Height (cm)
Answers will vary
Volume (cm3)
Answers will vary
Density of Butter (g/cm3)
Answers will vary
Density of Water (g/mL)
1 g/mL
You Be The Chemist® Activity Guide | page 65
LESSON 4 ACTIVITY SHEET: Buoyant Butter
ANSWER KEY: Below are suggested answers. Other answers may also be acceptable.
The formula for density is d = m/v.
2. What is the formula for density? What is the unit of measurement for density? ________________________________
Density is measured in grams per cubic centimeter (g/cm3) or grams per milliliter (g/mL).
______________________________________________________________________________________________________
______________________________________________________________________________________________________
The density of butter is
3. Based on your calculation, is the density of the butter greater or less than the density of water? __________________
less than the density of water.
______________________________________________________________________________________________________
______________________________________________________________________________________________________
Because the density of butter is less than the density of water, the butter will
4. Do you think the butter will sink or float? Why? ________________________________________________________
float in the water.
______________________________________________________________________________________________________
______________________________________________________________________________________________________
5. If you place the stick of butter in salt water, do you think it will sink or float? Why?
The stick of butter will float in the
__________________________
salt water. The addition of salt to water adds mass to the water. Since the formula for density is d = m/v, the density of the water increases.
______________________________________________________________________________________________________
______________________________________________________________________________________________________
Thus, the butter is even less dense than the salt water.
6. Is your hypothesis valid? Why or why not? If not, what would be your next steps? ____________________________
Answer 1: Valid because the data support my hypothesis.
______________________________________________________________________________________________________
Answer 2: Invalid because the data do not support my hypothesis. I would reject my hypothesis and could form a new one, such as …
______________________________________________________________________________________________________
You Be The Chemist® Activity Guide | page 66
LESSON 4 ACTIVITY SHEET: Buoyant Butter
ANSWER KEY Below are suggested answers. Other answers may also be acceptable.
SHARE YOUR KNOWLEDGE—BEGINNERS
Have students complete this section if you used the beginners’ differentiation information, or challenge them to find the answers to these
questions at home and discuss how these terms relate to the experiment in class the next day.
1. Define the following key terms. Then, provide an example of each by writing the example or drawing/pasting an
image of the example.
Term
Definition
Example (write or add image)
Measurement
A technique in which properties of a substance are
determined by comparing it to some sort of standard.
Accuracy
The closeness of a given measurement to the actual (true)
value for that quantity of substance; to measure a quantity
as close as possible to the true measurement (true value) of
that quantity.
Precision
The degree to which repeated measurements under
unchanged conditions show the same results.
2. List some objects that you think have a density greater than water.
An anchor, a coin, and a dumbbell are objects that have
________________________________________
a greater density than water. They will sink in water.
______________________________________________________________________________________________________
______________________________________________________________________________________________________
3. List some objects that you think have a density less than water.
An apple, a cork, and a beach ball are objects that have a
__________________________________________
density less than water. They will float in water.
______________________________________________________________________________________________________
______________________________________________________________________________________________________
4. If you cut the stick of butter in half, will its density change? Why or why not?
No, if you cut the stick of butter in half,
______________________________
both the mass and the volume of the butter change. The mass will be half of what it was before. The volume will also be half of what it was
______________________________________________________________________________________________________
before. Since the density fomula is d= m/v, the density will remain the same.
______________________________________________________________________________________________________
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