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4 Measuring
measuring Mass
BROWARD COUNTY ELEMENTARY SCIENCE BENCHMARK PLAN
Grade 3—Quarter 1
Activity 4
SC.A.1.2.1
The student determines that the properties of materials (e.g., density and volume) can be
compared and measured (e.g., using rulers, balances, and thermometers).
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SC.A.1.2.3
The student knows that the weight [mass] of an object always equals the sum of the weights
[masses] of its parts.
SC.H.1.2.1
The student knows that it is important to keep accurate records and descriptions to provide
information and clues on causes of discrepancies in repeated experiments.
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The student knows that a successful method to explore the natural world is to observe and
record, and then analyze and communicate the results.
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The student knows that to compare and contrast observations and results is an essential
skill in science.
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SC.H.3.2.2
The student knows that data are collected and interpreted in order to explain an event or
concept.
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ACTIVITY ASSESSMENT OPPORTUNITIES
The following suggestions are intended to help identify major concepts covered in the activity
that may need extra reinforcement. The goal is to provide opportunities to assess student
progress without creating the need for a separate, formal assessment session (or activity) for
each of the 40 hands-on activities at this grade level.
1. Ask, What do the processes of measuring length, capacity, volume, and mass all have in
common? (They all use standard measurement units; they all use special tools to do the
measuring; they all help compare items fairly.) Ask, Why are gram units better than paper
clip units for comparing masses? (Paper clips come in different sizes and are made of
different materials with different weights; paper clips are not as standardized as gram
units; you can be sure that one gram unit in Japan or France is the same as a gram unit in
the United States.)
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2. Use the Activity Sheet(s) to assess student understanding of the major concepts in the
activity.
In addition to the above assessment suggestions, the questions in bold and tasks that
students perform throughout the activity provide opportunities to identify areas that may
require additional review before proceeding further with the activity.
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activity 4 Measuring Mass
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iv
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4 Measuring
measuring Mass
1
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OBJECTIVES
Students set up and use an equal-arm
balance to measure the mass of various
objects in both uniform units and metric
standard units of measure.
washer, large
washer, small
For the class
1
bag, plastic, reclosable
1 stick clay
The students
For the teacher
þ use
an equal-arm balance to measure the
mass of objects
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1
hole punch*
1
paper clip, large
1 pair scissors*
1 spool thread
1
washer, large
1
washer, small
þ are
introduced to the gram, the metric
standard unit for measuring mass
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þ predict
and measure the masses of objects
in both uniform units of paper clips and
metric standard units of grams
the mass of an object with the
sum of the masses of its parts
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þ compare
*provided by the teacher
PREPARATION
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SCHEDULE
About 50 minutes
VOCABULARY
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1
Make a copy of Activity Sheet 4, Parts A
and B, for each student.
2
Cut 48 pieces of thread about 20 cm
(about 8 in.) long. Each balance will need
two soufflé cups to function as trays.
Punch three equidistant holes around the
rim of each soufflé cup (see Figure 4-1).
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equal-arm balance
gram (g)
mass
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MATERIALS
For each student
1
Activity Sheet 4 , Parts A and B
For each team of four
1
1
35
1
1
1 box
1
2
base, balance
beam, balance
centimeter cubes
crayon*
paper clip, large
paper clips, small
pin, balance
soufflé cups, balance
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Figure 4-1. Thread tied through holes in the rim of a
soufflé cup.
3
Assemble one of the balance setups for
a demonstration (see Figure 4-2 on next
page).
4
Link together a small washer and a large
washer with a large paper clip.
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£
5
Figure 4-2. An equal-arm balance.
Each team of four will need a balance
base, a balance beam, a balance pin,
two prepared soufflé cups, six 20-cm
pieces of thread, a small piece of clay, a
large washer, a small washer, a crayon,
a large paper clip, a box of small paper
clips, and 35 centimeter cubes.
BACKGROUND INFORMATION
The mass of an object is not the same as its
weight. Mass is a measure of the amount of
matter in an object. Weight is a measure of
the pull of gravity on an object. An object’s
mass is constant, no matter where the object
is. In contrast, the farther an object is from
Earth (or other body exerting gravitational
force), the less the object weighs. Thus,
unlike mass, an object’s weight varies with
altitude from Earth’s surface and also
changes from one planet to another.
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The basic metric unit for mass is the gram.
The gram is defined in terms of the
centimeter: one gram equals the mass of
one cubic centimeter of water at the
temperature of its maximum density (4°C).
One thousand milligrams equals one gram.
One thousand grams equals one kilogram.
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In this activity, students first use a uniform
unit of measure—a paper clip—and then
use the metric standard unit of measure for
mass—the gram—to measure the masses
of various objects. Using an equal-arm
balance, they determine the mass of the
object on one arm by counting the number
of uniform (or metric standard) units on the
other arm that bring the arms into balance.
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activity 4 Measuring Mass
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Activity Sheet 4, Part B
© Delta Education. Photocopying and distribution prohibited.
£
Activity Sheet 4, Part A
Guiding the Activity
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Additional Information
Write the word mass on the board. Then hold
up a book and explain to students that the
mass of an object, such as the book, is the
amount of matter in it.
Show the class the balance setup you
assembled. Write equal-arm balance on the
board. Explain that an equal-arm balance is
used to find the mass of an object.
The equal-arm balance gets its name from the
fact that the lengths of the beam, or arm, on
either side of the balance point are the same.
Point out to students the individual
components of the balance—the base, the
balance beam, the balance pin, and the cups.
Tell students they will assemble equal-arm
balances and use them to measure the
masses of various objects. Tell them that first
they will make trays with soufflé cups. Using
one of the demonstration balance cups, show
students how to tie pieces of thread through
the holes and tie the other ends of the
threads together at the top.
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Disassemble the demonstration setup and
show students how to reassemble it.
Suspend the soufflé cups from the notches
on the ends of the balance beam. Show
students the stick of clay and ask, If the
beam does not balance, how could you use
the clay to level it?
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Students may suggest sticking bits of clay
to the higher arm of the beam until it is
level.
Demonstrate that a bit of clay can add weight
to one arm or the other if necessary to make
the beam balance.
Tell students that in this activity they will
measure mass first with the uniform unit of
paper clips. Place a crayon in one cup of your
demonstration balance. Hold up a small
paper clip and ask, How can a paper clip be
used as a uniform unit to balance the mass
of the crayon?
Invite a volunteer to add paper clips to the
empty cup until the cups balance. Ask, What
can you conclude about the masses in
these balanced cups?
Students should suggest placing paper
clips in the empty cup until the cups
balance.
Students should say the masses are equal
since the cups are balanced.
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Additional Information
Guide students to understand that if they
count the number of paper clips in the cup,
they will know the mass of the crayon in
uniform units of paper clips.
Disassemble the setup (except for the
threaded soufflé cups) for later distribution
to a team. The threaded soufflé cups will
be handed out as is.
Give a copy of Activity Sheet 4, Part A, to
each student. Give each team a balance base,
a balance beam, a balance pin, two soufflé
cups, six 20-cm pieces of thread, a small
piece of clay, a large washer, a small washer,
a crayon, a large paper clip, a centimeter
cube, and a box of small paper clips.
One team will receive the components of
your demonstration model.
Have teams tie the pieces of thread through
the holes in the soufflé cups. Offer help as
needed. Have teams assemble their equalarm balances and suspend the soufflé cups
from the notches on the ends of the balance
beam. Ask, What should you do if your
beam is not level?
Remind students that they will use paper
clips as units of mass. Tell them the five
objects they have been given to measure are
also listed on their activity sheets. Ask
students first to predict the order of the
objects from least mass (“lightest”) to
greatest mass (“heaviest”) and then to
predict how many paper clips it will take to
balance each object. Tell them to record their
predictions on their activity sheets before
beginning their experiments.
Stick bits of clay to the higher arm of the
beam until it is level.
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The five objects to weigh are the large
washer, the small washer, the crayon, the
centimeter cube, and the large paper clip.
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Instruct students to find the mass of each
object using the small paper clips as uniform
units of measure and then counting the paper
clips. Have them record their results on the
activity sheet.
When students have finished measuring and
recording the masses, hold a brief class
discussion to interpret students’ results. Ask,
Which object had the greatest mass? Which
object had the least mass?
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activity 4 Measuring Mass
Students should be able to support their
answers with their recorded data.
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Guiding the Activity
Guiding the Activity
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Additional Information
Give a copy of Activity Sheet 4, Part B, to
each student. Distribute 34 additional
centimeter cubes to each team. Ask each
student to pick up a cube and feel how heavy
it is.
Write the word gram and (g) on the board.
Tell students that the cube has a mass of 1
gram, abbreviated g, and that the gram is the
international metric standard unit of mass.
Ask, What are some of the metric standard
units of measure you have used in previous
activities?
Student answers may include centimeters,
liters, and milliliters.
Tell students that by measuring an object’s
mass with cubes, they will know the mass of
the object in grams.
Instruct students to find the mass of each
object using the gram cubes. Encourage them
to first predict the mass in grams. Have
students record their predictions and results
on the activity sheet.
Have students compare the data from using
paper clips and grams as units of measure.
Ask, How are the two sets of data alike?
How are they different?
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Hold up a large washer and a small washer
linked together by a large paper clip. Ask,
How do you think the mass of these three
items linked together compares with the
total mass of the paper clip, the large
washer, and the small washer when
measured separately?
Ask, How could you test your predictions?
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Remind students to label their answers with
g for grams.
In both cases, the same objects are the
heaviest and lightest. The number of units is
different.
Accept all reasonable answers. Students may
realize that the two masses will be the same.
Students should suggest that they could add
up the masses of the three items in their data
chart. They could then link the three items
together and find the mass of the whole and
compare the two.
Have students record their predictions on
their activity sheets. Then have them
calculate the total mass of the large paper
clip, the small washer, and the large washer.
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Guiding the Activity
Additional Information
Then have students test their predictions.
Remind them to record their new
measurement on the activity sheet and to
label it with g for grams.
Discuss students’ results with them. Ask,
How did the total mass of the three
separate items compare with their mass
when linked together?
Ask, What conclusion can you draw from
these observations?
Students’ data should show that the total
masses are the same.
Students should suggest that the mass of an
object is equal to the sum of the masses of
the object’s parts.
Have students complete their activity sheets.
REINFORCEMENT
CLEANUP
Give students four or five objects found in
the classroom that are small enough to fit in
the soufflé cup. Tell students to order the
objects from least mass to greatest mass
by lifting them. Have them record their
predictions on a sheet of paper. Then have
them check the order by using the equal-arm
balance and centimeter cubes. Tell them to
record the results in grams.
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Have students disassemble the equal-arm
balances and return the parts along with
the centimeter cubes, the large paper clips,
the boxes of small paper clips, and the
large and small washers to the kit. Put the
clay in the reclosable plastic bag and return
it to the kit.
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SCIENCE JOURNALS
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Have students place their completed activity
sheets in their science journals.
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activity 4 Measuring Mass
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SCIENCE AT HOME
Challenge students to make an equal-arm
balance at home using a strong coat
hanger and two paper or plastic cups as
the balancing trays. Students can suspend
the hanger from a hook and use marbles as
uniform units of measure for comparing the
weights of small objects.
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7
Connections
Science Challenge
Tell students that a see-saw is somewhat like
an equal-arm balance. Have students tell
about experiences they have had with with
see-saws, including what happens if someone
moves closer to or farther from the end of a
beam. Discuss how they could use a see-saw
to find the mass of their bodies in either
uniform units of measure or metric standard
units of measure. If a see-saw is available,
have students try their ideas.
Science Extension
Tell students that one gram is approximately
equal to the mass of one cubic centimeter of
water. Give students an opportunity to verify
this. In a learning center, set up an equal-arm
balance with pans larger than the soufflé
cups. Also provide a beaker marked in cubic
centimeters, a pitcher of water, 100
centimeter cubes, and several washers and
paper clips. Let teams take turns doing the
following investigation: First, use the washers
and paper clips to balance the empty beaker.
Then fill the beaker to the 50 cc (50 mL) mark
with water, and put 50 cubes in the other
pan. The pans should balance. Let students
try balancing other volumes of water and
numbers of cubes.
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Science and Language Arts
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Ask students to use what they learned earlier
about prefixes to infer what milligram means
(one thousandth of a gram). Explain that the
prefix centi- is not used with gram. That is,
measurements are not made in units of
centigrams.
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Science and Math
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material. Also encourage them to try
balancing 100 mL of each material with
varying volumes of water and/or numbers of
centimeter cubes to determine its exact mass
per 100 mL. Students can then divide each
mass by 100 to calculate the material’s mass
per mL.
Encourage teams to measure the masses in
centimeter cubes (grams) of various small
objects of their own choice, such as an
eraser, a large metal bolt, a spoon, an empty
plastic cup, coins, and so forth. Remind
students to record the mass of each object.
Then have each team sequence the objects’
masses from greatest to least. Students can
use this information to make a bar graph
comparing the masses, with the horizontal
axis labeled Objects and the vertical axis
labeled Mass.
Let students balance a cup containing 100 mL
of water with a cup containing 100 mL of
another material to determine whether it has
less mass, greater mass, or about the same
mass as water. Provide a variety of dry
materials for students to test, such as
uncooked rice, salt, dried peas or beans,
popcorn, sand, and flour. Before students try
to balance each material with water, they
should predict the relative masses. Remind
students to record the result for each
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Activity Sheet 4, Part A
Name
Measuring Mass
Permission granted to purchaser to photocopy for classroom use.
I predict that the order of the five objects from least mass to greatest mass will be:
Least
Greatest
1. Complete the following chart using small paper clips to find the mass of each
object.
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Mass (in small paper clips)
Object
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Predicted
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large washer
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small washer
crayon
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Actual
© Delta Education
© Delta Education. Photocopying and distribution prohibited.
centimeter cube
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large paper clip
I found that the order of the five objects from least mass to greatest mass is:
Least
Greatest
Activity Sheet 4, Part B
Name
Measuring Mass
Mass (in grams)
Object
Predicted
Actual
large washer
small washer
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large paper clip
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crayon
Permission granted to purchaser to photocopy for classroom use.
2. Complete the following chart using centimeter cubes (grams) to find the mass
of each object.
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4. Measure
What is the total mass of the small washer and the large washer linked
together with the large paper clip?
5. Calculate
What is the sum of the masses of the small and large washer and the large
paper clip when they are measured separately?
6. Conclude
Was your prediction correct? Explain why or why not.
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© Delta Education
3. Predict
How will the sum of the masses of two washers and the large paper clip
compare with the mass of the three items together?