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1 A Centimeter Ruler
BROWARD COUNTY ELEMENTARY SCIENCE BENCHMARK PLAN
Grade 3—Quarter 1
Activity 1
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.H.1.2.4
The student knows that to compare and contrast observations and results is an essential
skill in science.
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
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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.
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1. Ask students to help you make a list on the board of different ways that a ruler is used.
(Their suggestions should include measuring dimensions as well as comparing distances,
sizes, heights, and so on.) Ask them to describe the advantages of using commonly
agreed on (standard) units. (Using standard units helps us compare things fairly and
equally.) Ask, You worked like a scientist in this activity. How do measuring tools like a
ruler make a scientist’s work easier? (Scientists need to be accurate. They need to be able
to compare things using the same units.)
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 1 A Centimeter Ruler
© Delta Education. Photocopying and distribution prohibited.
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1 A Centimeter Ruler
For the class
OBJECTIVES
20
1
1 pair
1 roll
1 roll
1 roll
In this activity, students are introduced to
the centimeter, an international standard
unit of measure in the metric system. They
construct a centimeter ruler and use it to
measure the dimensions of various objects.
The students
centimeter cubes
eraser, board*
scissors*
string
tape, transparent*
ticker tape
*provided by the teacher
þ discuss
the need for international standard
units of measure
þ are
PREPARATION
introduced to the metric system
þ construct
a centimeter ruler
and measure the lengths of various
objects in centimeters
1
Make a copy of Activity Sheet 1 for each
student.
2
Cut a length of ticker tape 30.5 cm (about
12 in.) long for each student. Cut a length
of string 20 cm (about 8 in.) long for each
team.
3
Cut two lengths of ticker tape for
demonstration, one 30.5 cm long and the
other 100 cm long. Tape the 30.5-cm
length of tape to the board. You will use
the longer piece in a later demonstration.
4
You will need a board eraser for a
demonstration.
5
Each student will need a centimeter cube,
a pencil, and a 30.5-cm length of ticker
tape. Each team will need a length of
string, a sponge block, a wooden block, a
paper clip, a tongue depressor, a fulcrum,
and a balance beam.
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SCHEDULE
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About 40 minutes
VOCABULARY
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centimeter (cm)
customary system
international standard unit of measure
meter (m)
metric system
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MATERIALS
For each student
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1
Activity Sheet 1
centimeter cube
pencil*
For each team of four
1
1
1
1
1
1
beam, balance
fulcrum
paper clip, small
sponge block
tongue depressor
wooden block
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BACKGROUND INFORMATION
In the 1500s, the English began trying to
standardize measurements for easier trade
with other countries. By the 1800s, they had
determined precise sizes for length, weight,
volume, and temperature. These standard
units of measurement became part of the
English, or customary, system. One of the
drawbacks of this system is that it was, and
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still is, very awkward to use. Conversions
between units in this system involve tedious
mathematical calculations.
Activity Sheet 1
In the late 1790s, the French announced the
development of a simpler, more reasonable
system based on the meter (length), the gram
(weight), the liter (capacity), and the Celsius
scale (temperature). Because this metric system
is a decimal system—a system based on the
number 10—its units are obtained by
multiplying or dividing the basic unit by 10, 100,
1000, and so on. All major countries except the
United States have officially adopted these units
as international standard units of measure.
The United States customary system and the
metric system are the two principal systems of
measurement in the world today. The customary
system measures length and distance in inches,
feet, yards, and miles. The metric system uses
the meter as a standard measure of length and
distance. A meter is equivalent to about 40
inches, slightly longer than a yard. The word
meter is derived from a Greek word meaning “to
measure.” The meter was originally defined as
one ten-millionth (1⁄10,000,000) of the distance
from the equator to the North Pole.
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The centimeter, approximately equal to twofifths of an inch, is one-hundredth (1⁄100) of a
meter. Thus, there are 100 centimeters in a
meter.
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activity 1 A Centimeter Ruler
© Delta Education. Photocopying and distribution prohibited.
In this activity, students construct a international
standard metric measuring tool—a centimeter
ruler—and use it to measure the dimensions of
various objects.
Guiding the Activity
1
Additional Information
Hold up 20 centimeter cubes and a board
eraser. Ask, How could we use these cubes
to measure the length of this eraser?
Students should suggest lining the cubes
up from one end of the eraser to the other
and counting the number of cubes used.
Invite a volunteer to measure the length of
the eraser in cubes. Write the length of the
eraser in cubes on the board.
2
Ask, Do people carry around cubes and line
them up to measure the length of things?
No. Students should recognize how
cumbersome measuring would be if we had
to carry around these materials.
Ask, What tools do people use to measure
length?
Students should say that people use a ruler
or a measuring tape.
Distribute a length of ticker tape and one
cube to each student. Tell students that they
are going to make a ruler.
Each student will need a pencil.
Demonstrate how to line up the cube against
the left-hand end of the ticker tape that you
taped to the board. Ask, Where is “0 cubes”
found on the ruler? Show students how to
mark and number the tape using the cubes
and their pencils.
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Students should say “0 cubes” is found at
the left-hand end of the ruler.
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Tell students to make their rulers. Explain
that the distance between each line and the
next on the ticker tape should be exactly
equal to the width of the cube. Have them
number the lines in increments of one, from 1
to 30.
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When students have finished making their
rulers, ask a volunteer to measure the eraser
with his or her ruler. Write the measurement
on the board in number of cubes.
Tell students to compare this measurement
with the measurement made earlier with the
cubes. Ask, Are the two measurements the
same? Can we fairly compare the
measurement made with the cubes with the
measurement made with the ruler?
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Figure 1-1. Making a centimeter ruler.
Students should answer yes, the units of
measure in both cases were cubes of the
same size, and so the two measurements
should be the same.
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Guiding the Activity
Write international standard unit of measure
on the board. Ask, How would you define an
international standard unit of measure?
Additional Information
Answers will vary. Students may say it is a
standard unit of measure used by more
than one nation.
Tell students that most of the countries in the
world have agreed to use the same, or
international standard, units of measure.
Write metric system on the board. Tell
students that the system that uses
international standard units of measure is
called the metric system.
Write customary system on the board. Tell
students that in the United States we use two
different measuring systems. We use the
metric system mostly in science and
engineering, but in our daily lives we still use
what is called the customary system of
measurement. Most other countries use the
metric system for measuring in daily life.
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Tell students that they have just created a
centimeter ruler and that next they will use
their centimeter rulers to measure various
objects.
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activity 1 A Centimeter Ruler
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Write centimeter and cm on the board. Hold
up the cube and tell students that this cube
is called a centimeter cube because it is one
centimeter long. A centimeter is a standard
unit of measure in the metric system. Tell
students that the distance between any two
tick marks on their rulers is called one
centimeter, abbreviated cm.
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Most students will be familiar with United
States standard measurements. Encourage
answers that name inches, feet, yards, and
miles as measurements of length and
distance.
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Ask, What other measuring system do we
use in the United States that has standard
units of measure for length and distance?
Can you name those units?
Guiding the Activity
3
Additional Information
Give a copy of Activity Sheet 1 to each
student. Distribute a sponge block, a wooden
block, a paper clip, a tongue depressor, a
fulcrum, a balance beam, and a length of
string to each team. Instruct students to first
predict the length of each of the objects in
centimeters and then record their predictions
on their activity sheets. Point to the
abbreviation cm on the board and tell
students to label their answers with cm for
centimeter(s).
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Tell students to measure the objects to the
nearest centimeter and record their results in
the chart on the activity sheet. All team
members should make and test their
predictions and discuss the results.
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Tell students to answer the question at the
end of the activity sheet.
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Figure 1-2. Measuring objects with a centimeter ruler.
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When students have completed measuring
and recording, ask, How do your results
compare with your teammates’ results?
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Remind students that it is important to line
up the zero end on a measuring tool with
the edge of the object to be measured.
Students should find that all team
members’ measurements are the same. If
there are any discrepancies, discuss
possible sources of error, such as not lining
up the zero end with the edge of the
object.
Tape the 100-cm length of ticker tape to the
board below the 30.5-cm tape. Write 30.5 cm
and 1 meter on the board beside the
respective tapes. Tell students that the longer
piece of ticker tape is exactly 1 meter long. A
meter is another standard unit of measure in
the metric system.
Ask, If centi- means one-hundredth, how
many centimeters would it take to reach
from end to end on this 1-meter tape?
Students should reason that it would take
100 centimeters.
Tell students that the meter is used to
measure longer lengths and distances than
the centimeter.
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REINFORCEMENT
CLEANUP
Give students a 12-inch ruler, or have
students make a 12-inch ruler on ticker tape.
Using first their centimeter rulers and then
their inch rulers, have them measure three
objects, recording their lengths in both
centimeters and inches.
Students may keep their centimeter rulers.
Return the centimeter cubes, the sponge
blocks, the wooden blocks, the paper clips,
the tongue depressors, the fulcrums, the
balance beams, the roll of ticker tape, and
the roll of string to the kit.
SCIENCE AT HOME
Have students place their completed activity
sheets in their science journals.
Encourage students to take their rulers
home and measure the dimensions of
familiar objects at home. Students could
also measure the height of every family
member at home in centimeters.
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activity 1 A Centimeter Ruler
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SCIENCE JOURNALS
Connections
Science Challenge
Science, Technology, and Society
Ask students to put one hand flat on the desk
with the fingers outstretched and then trace
around the entire hand—from the wrist on
one side around the fingers and thumb to the
other side of the wrist—with the index finger
of the other hand. After each student has
done this, challenge teams to devise a way to
measure this distance (the perimeter of the
hand) in centimeters as accurately as they
can. Let students experiment freely and then
share their methods and results in a class
discussion. (Students may first try to bend
their ticker-tape centimeter ruler around the
hand but will find that this method is rather
awkward and inexact. A better method is to
lay a string along the hand’s perimeter, cut or
mark its final length, and then measure the
string with the ruler. An even easier method is
to draw the hand’s outline on paper, lay a
string along the outline, and then measure
the string.)
Ask students to name as many devices as
they can that are used to measure length,
width, and height, and list their suggestions
on the board. Possibilities include rulers of
different lengths (6 in., 12 in., 18 in., and so
forth), a yardstick or meterstick, a carpenter’s
metal tape measure, a fabric tape measure
used in sewing, a carpenter’s square with
standard units marked on each side, and a
drafting ruler with different scaled units on
each edge, used in making scale drawings.
Bring in a variety of such measuring devices,
or ask volunteers to bring them from home, so
the class can examine them, discuss their
different characteristics and applications, and
use them to measure dimensions and
distances in the classroom and outdoors.
Focus students’ attention on the specific
characteristics of each device that make it
appropriate for its intended uses. For
example, a sewing tape measure is flexible so
it can be wrapped around the body to make
measurements. A carpenter’s tape measure is
made of fairly rigid metal so it will stay in a
straight line when the tape is extended.
© Delta Education. Photocopying and distribution prohibited.
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Students are undoubtedly more used to
working with English units than metric units
in everyday life. However, they may be
familiar with rulers marked in both English
and metric units. Give each team such a ruler,
and ask students to determine roughly how
many centimeters equal one inch. (about 2.5)
Make up several simple word problems for
students to solve that involve converting from
inches to centimeters and vice versa. For
example, “How many centimeters equal 10
inches?” (25) “How many inches equal 10
centimeters?” (4) “What are the dimensions
in centimeters of an ordinary 8.5-by-11-inch
sheet of paper?” (21.5 cm by about 28 cm)
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Science and Math
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activity 1 A Centimeter Ruler
© Delta Education. Photocopying and distribution prohibited.
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Activity Sheet 1
Name
A Centimeter Ruler
Permission granted to purchaser to photocopy for classroom use.
Length (in centimeters)
Object Measured
Predicted
Actual
balance beam
fulcrum
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paper clip
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sponge block
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string
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tongue depressor
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© Delta Education
© Delta Education. Photocopying and distribution prohibited.
wooden block
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Why do we measure in centimeters and not in paper clips?
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