Science tools
Using a Balance Scale
In almost every task in life, people use tools. Doctors cut with scalpels, construction workers
dig with shovels, and artists paint with brushes. Science is no different. Many tools can help
you measure the results of your observations and experiments. These tools can make your
job easier and make your results more precise.
Purpose
Materials
(per group)
qData Sheets 1 and 2
qbalance scale
q5 toothpicks
qset of 10 lightweight classroom objects
(1 unsharpened pencil and 9 other
items, such as student scissors, glue
stick, watercolor paintbrush, marker,
or crayon)
qbox or bag of small paper clips
To accurately use a balance scale to
compare the weights of objects.
Process Skills
Predict, observe, measure, collect data,
interpret data, communicate, identify
and control variables, draw conclusions
Background
The amount of material that a thing
is made of is called its mass. When we
measure how heavy a mass is, we call that
number its weight. On Earth, the weight of an object is the same as its mass.* We can use
a scale to measure weight. Scales often measure weight in grams, kilograms, ounces,
or pounds. Scientists usually use grams and kilograms to measure weight. One gram (g)
is about equal to the weight of two small paper clips. One liter (1,000 g) of water weighs
one kilogram (kg).
A balance scale is a tool that can be used to compare the weights of two objects.
A balance scale is like a seesaw. When one object is heavier than the other, the scale
is unbalanced, and the heavier object drops below the level of the lighter object.
When the scale is balanced, we know that the objects on both sides weigh the same.
Or we can weigh an object by placing it on one side of the scale and adding standard
units of measure (such as gram
pointer
fulcrum
or kilogram weights) to the other
side until the scale is balanced.
Time – Preparation: 10 minutes;
Part 1: 10 minutes; Part 2: 30 minutes
pan
Grouping – Small groups
base
beam
Figure A
*On other planets, an object that has the same mass as it did on Earth might weigh more or less, depending on the force of gravity there.
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EXPLORATION
Science Tools—Using a Balance Scale
Procedure
Preparation
4.If you have had to adjust your scale by
adding toothpicks, make sure to leave
the toothpicks on the scale while you
do Part 1 and Part 2.
1.Get a balance scale and five toothpicks
from your teacher. Make sure to place
your balance scale on a level surface.
Part 1: Comparing Weights
1.Gather a set of ten lightweight classroom
objects, including an unsharpened
pencil. Write the names of all the objects
in the first column of Data Sheet 1.
2.In your group, take turns pointing
to each of the balance scale’s parts
(See Figure A on page 1). Locate the
fulcrum, base, beam, pans, pointer,
and adjustment dial (if there is one).
If you need help, look at Figure A
and compare it to your scale.
2.Take turns holding each object in
your hand. As a group, discuss which
objects feel heaviest and which objects
feel lightest.
3.In order to get accurate measurements
of weight, check to make sure that your
scale is “zeroed out.” This means the
line or lines in the middle of the scale
must be pointing to the exact middle
before you weigh anything. Your scale
may already be perfectly balanced. But
if your scale does need to be adjusted,
first see whether it has a dial that
you can turn to zero it out. If there
is no dial, try placing a toothpick onto
the higher side of your scale to make
it even with the other side. If the
toothpick is too heavy, break it in
half and try again until the scale is
zeroed out. You may need to add
more toothpicks or other items until
the scale is level.
3.On Data Sheet 1, record predictions.
Which objects will weigh more than the
unsharpened pencil? Which objects will
weigh less than the pencil? Will any
objects weigh the same as the pencil?
4.Now use your scale to compare the
weights of the other objects to the
weight of the unsharpened pencil.
Start by placing the unsharpened
pencil on one side of your zeroed-out
scale. One at a time, place each of the
other objects on the opposite side of
the scale. Compare the weights of the
other objects to the weight of the pencil
(See Figure B).
Figure B
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EXPLORATION
Science Tools—Using a Balance Scale
5.Which objects weighed more than the
pencil (making that side of the scale
drop lower than the side with the
pencil)? Which objects weighed less
than the pencil (making the pencil
side of the scale drop lower)? Which
objects weighed the same as the pencil
(making the two sides of the scale
even, in the zeroed-out position)?
On each row of Data Sheet 1, place
a check mark (3) in the correct box
to compare each object’s weight with
the weight of the pencil.
3.Place the unsharpened pencil on one
side of the scale. Add pairs of paper
clips to the other side of the scale until
the scale is balanced (see Figure C).
You will know that your scale is
balanced when the lines match the
zeroed-out position. Add or remove
a single paper clip if necessary to add
or subtract about half a gram.
Part 2: Measuring the Weights of Objects
1.Get a box or bag of small paper clips
from your teacher. Connect some of
the paper clips in pairs.
2.Use Data Sheet 2 to make a prediction
about how much the pencil will
actually weigh. Predict the number
of paper clips it will take to balance
the scale and how many grams the
pencil will actually weigh.
Figure C
4.Use Data Sheet 2 to record the number
of paper clips it actually took to
balance the scale. Also record the
actual weight of the pencil (in grams).
TIP: Each set of 2 paper clips weighs
about 1 gram (1 g). A single paper
clip weighs about one-half of a gram
(0.5 g). For example, if you think that
your pencil will weigh the same as
15 paper clips, the predicted weight
would be about 7.5 grams.
5.Repeat steps 2, 3 and 4 for each of the
remaining lightweight objects. First,
record a prediction of its weight, both
in paper clips and in grams. Then
place each object on one side of your
scale and use paper clips to find its
actual weight. Record the results on
Data Sheet 2.
= 1 gram
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EXPLORATION
Science Tools—Using a Balance Scale Data Sheet 1
Name________________________________________ Date_____________
Part 1: Comparing Weights
Predict:
Which objects will weigh more than the pencil?
Which objects will weigh less than the pencil?
Which objects will weigh the same as the pencil?
Collect Data
Object
Weighs more than
the unsharpened
pencil
Weighs less than
the unsharpened
pencil
Unsharpened
pencil
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Weighs the same as
the unsharpened
pencil
3
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EXPLORATION
Science Tools—Using a Balance Scale Data Sheet 2
Name________________________________________ Date_____________
Part 2: Measuring the Weights of Objects
Collect Data
Object
Prediction:
Number of
paper clips
Prediction:
Weight in
grams (g)
(predicted number
of paper clips ÷ 2)
Actual:
Number of
paper clips
Actual:
Weight in
grams (g)
(actual number of
paper clips ÷ 2)
Unsharpened
pencil
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EXPLORATION
Science Tools—Using a Balance Scale Questions
Name________________________________________ Date_____________
Analyze Data
1. Describe exactly what you had to do to zero out your scale.
2. Did any objects weigh an equal amount? If yes, which objects? If no, which objects
were closest to equal?
3. Which object weighed the most? How many grams did it weigh? Which object
weighed the least? How many grams did it weigh?
Most:
Weight:
g
Least:
Weight:
g
4. Which object’s predicted weight was the closest to its actual weight? Why do you think
your prediction was the closest for this object?
5. Suppose one of your objects took 11 paper clips to balance. What would the weight
of this object be?
6. Look at Data Sheet 2 to find out how much your unsharpened pencil actually
weighed (in grams). How much would 3, 10, and 47 unsharpened pencils weigh?
1 pencil = ______ grams
10 pencils = ______ grams
3 pencils = ______ grams
47 pencils = ______ grams
Draw Conclusions
1. Why is it useful to know how to use a scale? List three reasons you might use
scales outside of school.
2. In your own words, explain how a balance scale works.
3. If your teacher asked you to build your own balance scale using materials from
the classroom, how would you build it? (Use the back of the paper.)
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science tools
Using a Balance Scale
Teaching Tips
This process activity will help students understand how a balance scale works.
Students will learn how to zero out a scale and predict weight in grams. Students
will also gain experience as they explore the weights of common classroom objects
and use the data to calculate and compare weights. As they relate weight to common
objects, students may come to appreciate how a scale helps people in a variety of
settings. Practicing using a scale and comparing the weights of objects will also
help students estimate the weights of solids in many applications.
Set-up and
procedures
materials
efore students compare and measure the weights of objects, you may want
B
to conduct your own measurements with the items they will be weighing so you will be able to judge whether students’ results are reasonable.
¢ Provide time for students to zero out their scales before beginning Part 1.
¢ Reinforce vocabulary (balance scale, base, fulcrum, beam, pans, pointer, zero out,
adjustment dial) while modeling how to zero out the scale. It may be helpful
to refer to the labeled diagram in Figure A, but explain to students that
scales come in many varieties. The balance scale they use may not look the same as the one in Figure A.
¢ If anything in the student set of objects to weigh is much heavier than the
unsharpened pencil, students will need too many paper clips to assess the
weight. Instead, encourage them to use unsharpened pencils as weights,
each one representing a certain number of paper clips (see Part 1, step 4 of the Procedure section). Individual paper clips may then be added to the pan holding the pencils until the scale is balanced. Instruct students to record the total weight in paper clips.
¢
Many districts have a science resource center to contact if balance scales
are not available at the school. Simple balance scales can also be constructed
using directions available online (search for “homemade balance scale”).
Otherwise, scales can be purchased at local or online teacher supply stores.
¢ Prepare sets of ten lightweight classroom objects for each group beforehand.
Make sure each set is the same so that groups can compare data. Each set must include one unsharpened pencil and nine other items, such as
student scissors, a glue stick, a watercolor paintbrush, a cap eraser, a marker, a crayon, a colored pencil, or a piece of paper.
¢ Be sure students use small paper clips in Part 2.
¢ A large baggie may be used to hold the set of objects for each group.
However, students should weigh each object without this container.
¢ Additional unsharpened pencils should be available to students for use
in Part 2, step 5 if they have chosen heavier objects.
¢
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EXPLORATION
extensions and
variations
Science Tools—Using a Balance Scale
ariation/Inquiry Science: After students have compared the dry weight of
V
classroom items, allow them to use their balance scale to compare liquids
using small plastic condiment containers. Examples include water, milk,
juice, syrup, or oil. For example, does 100 mL of water weigh more or less than 100 mL of milk? (Note that liquid is measured by volume, not
weight. Milliliters [metric] and fluid ounces [standard] are used, so paper
clips are not valid as measurement tools.)
¢ Variation/Math: Have students determine the weight of large paper clips
compared to the weight of small paper clips. Most small paper clips
weigh .5 grams, and most large paper clips weigh 1.5 grams. Encourage
students to draw balanced equations that show the relationship between
small and large paper clips. Then allow students time to determine the
weights of their objects using both large and small paper clips.
¢ Community Service/Field Trip: Food banks weigh donations. Take a trip
to a local food bank, equipped with items to donate, and talk to the food manager about how weight is used there. If possible, ask whether
students may weigh some of the food donations. Recycling centers may
also provide opportunities for students to participate in weighing for an
authentic purpose.
¢ Inquiry Science: Allow students to explore different types of same-sized
paper. How many pieces of copy paper does it take to balance out one
sheet of card stock? Cardboard? Paper towels? Does lined paper weigh
the same as copy paper? Does all copy paper weigh the same amount?
Does folded paper weigh the same as flat paper?
¢ Writing: Have students write a poem or a short story that compares the
weight of an average mouse (20 grams) to other objects. For extensive
writing instruction, visit
.
¢ ELL/ESL: Create a word wall. Include content vocabulary such as balance
scale, zero out, fulcrum, beam, pans, pointer, adjustment dial, and gram. Also
include vocabulary relevant to the lesson, such as unsharpened pencil and
.
paper clip. For more vocabulary resources, visit
¢ Technology: Have students create a PhotoStory or PowerPoint presentation
about the balance scale. Students may share the results of their
exploration, the history of the balance scale, and pictures of various
balance scales.
¢ Home Connection: Challenge students to create their own balance scale at
home using everyday objects only. Ask students to bring their homemade
scale to class to be used in further practice.
¢
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EXPLORATION
Science Tools—Using a Balance Scale Data Sheet 1
Answer key
Results will vary, depending on the set of objects each group is given. For each object, students should
use their prior knowledge to make a reasonable prediction. The table below reflects possible data, based
on common lightweight classroom objects. Note that the results recorded below may vary from your own
school supplies; conduct your own measurements before assessing student data sheets.
EXPLORATION
Science Tools—Using a Balance Scale Data Sheet 1
Name________________________________________ Date_____________
Part 1: Comparing Weights
Predict:
Which objects will weigh more than the pencil? Student predictions will vary.
Which objects will weigh less than the pencil? Student predictions will vary.
Which objects will weigh the same as the pencil? Student predictions will vary.
Collect Data
Object
Weighs more than
the unsharpened
pencil
Weighs less than
the unsharpened
pencil
Unsharpened
pencil
Student scissors
Glue stick
3
3
3
Watercolor
paintbrush
3
3
Cap eraser
Marker
3
3
Crayon
Colored pencil
3
3
3
Copy paper, 1 sheet
Sharpened pencil
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Weighs the same as
the unsharpened
pencil
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EXPLORATION
Science Tools—Using a Balance Scale Data Sheet 2
Answer key
Results will vary, depending on the set of lightweight objects each group is given. The table below reflects
possible data, based on common lightweight classroom objects. If the sets that you have assembled for
your classroom vary from the objects below, conduct your own measurements before assessing student
data sheets.
EXPLORATION
Science Tools—Using a Balance Scale Data Sheet 2
Name________________________________________ Date_____________
Part 2: Measuring the Weights of Objects
Collect Data
Object
Unsharpened
pencil
Student
scissors
Glue stick
Watercolor
paintbrush
Cap eraser
Marker
Crayon
Colored pencil
Copy paper,
1 sheet
Prediction:
Number of
paper clips
For each
object,
students
should use
their prior
knowledge
to make a
reasonable
prediction.
Prediction:
Weight in
grams (g)
(predicted number
of paper clips ÷ 2)
Each
predicted
weight in this
category
should be
calculated
on the basis
of the
predictions
made in the
first column.
For example,
if a student
predicts that
a cap eraser
will weigh the
same as five
paper clips,
the predicted
weight will be
half of that
amount
(5 ÷ 2 = 2.5 g).
Sharpened
pencil
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5
Actual:
Number of
paper clips
Actual:
Weight in
grams (g)
(actual number of
paper clips ÷ 2)
11
5.5 g
54
27 g
30
15 g
4
2g
6
3g
24
12 g
11
5.5 g
12
6g
2
1g
10
5g
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EXPLORATION
Science Tools—Using a Balance Scale Questions
Answer key And Explanations
Analyze Data
1.Describe exactly what you had to do to zero out your scale.
Answers will vary, depending on the type of balance scale available in your classroom and students’
methods for zeroing out their scales. Answers should include an explanation of the process.
2.Did any objects weigh an equal amount? If yes, which objects? If no, which objects were
closest to equal?
Because each set of lightweight classroom objects will vary, conduct your own measurements before
assessing students’ answers to this question.
3.Which object weighed the most? How many grams did it weigh? Which object weighed
the least? How many grams did it weigh?
Because each set of lightweight classroom objects will vary, conduct your own measurements before
assessing students’ answers to this question.
Most: Weight: g
Least: Weight: g
4.Which object’s predicted weight was the closest to its actual weight? Why do you think
your prediction was the closest for this object?
Answers will vary and should include an explanation.
5.Suppose one of your objects took 11 paper clips to balance. What would the weight
of this object be?
11 ÷ 2 = 5.5 grams
6.Look at Data Sheet 2 to find out how much your unsharpened pencil actually weighed
(in grams). How much would 3, 10, and 47 unsharpened pencils weigh?
Because each set of lightweight classrooms objects will vary, conduct your own measurement of
the unsharpened pencil before assessing students’ answers to this question. The answers provided
below are based on an unsharpened pencil that balances with 11 paper clips. Since 11 paper clips
weigh 5.5 grams, students should calculate their answer by multiplying the number of pencils by
5.5. Thus, the results would be as follows:
1 pencil = 5.5 grams 3 pencils = 16.5 grams
10 pencils = 55 grams 47 pencils = 258.5 grams
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EXPLORATION
Science Tools—Using a Balance Scale Questions
Answer key And Explanations
Draw Conclusions
1. W
hy is it useful to know how to use a scale? List three reasons you might use scales
outside of school.
Answers will vary. It is useful to know how to use a scale for many reasons. Doctors keep track
of children’s weight to make sure that they are growing. People weigh food at the grocery store
or deli. Airlines use scales to make sure that a plane doesn’t carry too much baggage.
2. In your own words, explain how a balance scale works.
Answers will vary. The weights of objects can be compared using a balance scale. Assuming that
the pans are an equal distance from the fulcrum, an object that weighs more will be on the lower
side of the scale. If an object weighs less, it will be on the higher side of the scale. If objects weigh
the same amount, the scale will be parallel to the ground or tabletop.
3. If your teacher asked you to build your own balance scale using materials from the
classroom, how would you build it? (Use the back of the paper.)
Answers will vary but should indicate a basic knowledge of a balance scale’s parts, especially
the fulcrum and beam. Students might include a sketch or diagram.
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