Name: _______________________________________ Class: ______ Date: ____________ Lab # ___
Making Metric Measurements
Introduction
In many biology investigations, precise measurements must be made before observations can be
interpreted. For everyday measuring, we still use English units such as the inch, quart, and pound. For
scientific work, and for everyday measuring in most countries, the International System of Units (SI) is
used. Eventually our country will use SI units for everyday measuring too.
Like our money system, SI is a metric system. All units are based on the number 10. In the SI system it
is easy to change one unit to another because all units are related to one another by a power of 10.
In this investigation, you will review SI units for measuring length, liquid volume, and mass. You will
also learn how to use some common laboratory equipment used for measuring.
Pre-Lab Discussion
Read the entire investigation. Then, work with a partner to answer the following questions.
1. Why do scientists and other people in most countries use the metric system for measurements?
____________________________________________________________________________________
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2. Why is it easy to change from one unit to another in the SI system?
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Materials
Meter Stick
Graduated Cylinder
Metric ruler
Beaker
Water
Electronic balance
Pipette
Erlenmeyer (conical) Flask
Small Test Tube
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Handle all glassware carefully.
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Safety
Procedure
Part A. Measuring Length
1. Obtain one of the small plastic rulers. Notice that the ruler has metric units on one edge and
English units (inches) on the other edge. On the metric edge, the numbered lines are centimeters
(cm) and the small unnumbered lines are millimeters (mm).
a) According to your ruler, how many millimeters are there in one centimeter? ________ mm
b) According to your ruler, how many centimeters are on the ruler? ________ cm
c) According to your ruler, how many millimeters are on the ruler? _________ mm
Now complete the following
1 cm
=
_________________ mm
15 cm =
_________________ mm
2. Obtain a meter stick. Notice the meter stick has units on both sides of it. One side has the metric
units and the other has the English units (inches). On the metric side, the numbered lines are
centimeters (cm) and the smaller unnumbered lines are millimeters (mm).
a) According to your meter stick, how many millimeters are there in one centimeter? ______ mm
b) According to your meter stick, how many centimeters are on the meter stick? ________ cm
=
__________ cm
100 mm
=
__________ cm
100 cm
=
__________ m (meter)
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10 mm
39
Now complete this
3. Use the meter stick to measure the length, width, and height of your laboratory table or desk in
meters. Record your measurements to the nearest hundredth of a meter in Data Table 1.
4. Convert (change) the measurements from meters to centimeters and then to millimeters. Record
these measurements in Data Table 1
Data Table 1
Lab Table Measurements
Dimension
m
cm
mm
Length
Width
Height
5. Use a metric ruler to measure the length of a small test tube and the diameter of its mouth in
Centimeters. Record your measurements to the nearest millimeter in Data Table 2.
6. Convert (change) the measurements from centimeters to millimeters. Record these measurements
in Data Table 2.
Data Table 2
Test Tube Measurements
Dimension
m
cm
mm
Length
Diameter of Mouth
Part B. Measuring the Volume of a Liquid
This curved surface is called a meniscus. To measure
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2. The surface of the liquid will be slightly curved.
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1. Fill the test tube to the top with water. Pour the water into the graduated cylinder.
the volume accurately, your eye must be at the same
level as the bottom of the meniscus (see Figure 1)
Record the volume of the water from the test tube
to the nearest milliliter in Data Table 3 below.
Data Table 3
Measurement of Volume
Object
Volume (mL)
Water in Test Tube
3.
Find the amount of liquid (to the nearest milliliter) in each of the graduated cylinder sections 1 – 4
shown below
____________
_____________
_____________
____________
Part C. Measuring Mass
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Problem:
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1. How much do you think is the mass of 50 mL of water? ________________ g
(Note: there is no right or wrong answer here. This is just your prediction! Take a guess)
You are provided with three laboratory containers, an Erlenmeyer (conical) flask, a beaker, and a
graduated cylinder.
Which container (Erlenmeyer flask, a beaker, or graduated cylinder) do you think will be the most
accurate for measuring 50 mL of water? Why?
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To find out whether or not your prediction is correct, do the following
2. Be sure that the number on the screen of the balance is at 0.00 g (see Figure below)
3. Place the beaker on the pan of the balance and record its mass (dry mass) in Data Table 4.
4. Now pour some water into the beaker to the 50 mL mark, and then find the mass of the beaker
with water. Record this mass in Data Table 4.
5. Repeat steps 2 through 4 for the graduated cylinder and the Erlenmeyer (conical) flask.
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6. Find out the mass of water and fill in the column for the mass of water for each container.
Data Table 4
Dry mass of container
(g)
Mass of container
filled to 50 mL water
(g)
Mass of water only (g)
Beaker
Erlenmeyer(conical)Flask
Graduated Cylinder
7. Based on your results in Data Table 4, which container is the most accurate for measuring 50 mL of
water? Was your prediction supported by your results? Explain.
________________________________________________________________________________
________________________________________________________________________________
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8. Based on your results in Data Table 4, how much is the mass of 50 mL of water? ____________ g
Was your prediction supported by your result? Explain.
______________________________________________________________________________
______________________________________________________________________________
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Your results most likely contain some measurement error. The estimated mass of 50 mL of water in
each container is probably just above or below the ideal mass. See if you can figure it out.
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Ideally, without measurement error, 50 mL of water will always be ___________ grams of water.
Analysis and Conclusions
1. Calculating: How do you convert (change)
a) Meters to centimeters?
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b) Centimeters to millimeters?
_____________________________________________________________________________
2. Observing: What is the largest volume of liquid your graduated cylinder can measure? _________
3.
Observing: What is the smallest volume of a liquid your graduated cylinder can measure? ______
4. Calculating: Based on the measurements you did and recorded in Data Tale 4 above; what is the
mass of 50 mL of water? ___________________________________________________________
Explain your answer:
_____________________________________________________________
________________________________________________________________________________
5. Predicting: How would you find the mass of a certain amount of water that you poured into a
paper cup? _______________________________________________________________________
_________________________________________________________________________________
_________________________________________________________________________________
_________________________________________________________________________________
6. Calculating: In this investigation you found the mass of 50 mL of water. Based on your
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observations, what is the mass of 1 mL of water? __________________________________