Measurements and the Metric System
Name: ___________________________
Date:__________ Block:_________
Purpose: In this lab session, you will learn how to use instruments to make quantitative
observations. The instruments you will use today are the quad beam balance, the
electronic balance, the graduated cylinder, pipet, meter stick, 30 cm ruler, thermometer,
nurse’s balance.
Equipment and Materials Needed:
Quad beam balance, electronic balance, graduated cylinder, tap water, distilled water,
pipet, pipet bulb, meter stick, ruler, measuring tape, thermometer, nurse’s balance, and
beaker.
1. Using an electronic balance:
Rules for using an electronic balance:
1. Never place chemicals directly on
the balance pan. Place chemicals on
weighing paper or in a beaker.
2. Do not place hot objects on the
balance pan. The object being
weighed must be a the same temperature as the balance to ensure accurate mass
measurements.
3. Make sure the balance is level. If it is not level, contact your instructor.
4. The electronic balance that we use needs to be zeroed. This is a wonderful feature
of this balance. Suppose you want to measure out 5.00 grams of sodium chloride into a
beaker. Turn on the balance, place the beaker on the balance, wait a few seconds, and
then push the tare button. This will automatically zero the balance. Now all you do is
add the sodium chloride to the beaker until it reads 5.00 grams.
MAJOR RULES:
-Do not push down on the balance with your hand. For some reason, students love to
do this and then we don’t have a balance to use in class. Fancy that????
-Never exceed the mass of the balance by putting too much weight. Always check to
see what the maximum weight of the balance before attempting to use it.
1. Turn on the electronic balance. Allow it to zero itself.
2. Take a nickel and place it directly on the balance. Allow it to come to equilibrium.
Now record the mass of the nickel in the space below.
Mass of a nickel: ____________________
(make sure you record the units of the balance with your measurement.)
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2. Quad Beam Balance:
A balance is an instrument used to measure the mass of a substance. Mass is defined
as the quantity of matter. An object’s mass is determined when it is placed on a
balance and then compared to a known mass. The base unit of mass in the SI system
is the kilogram. Most balances in chemistry labs use grams as the unit given.
Rules for using a quad-beam balance:
1. When transporting a balance to your lab station,
always use 2 hands to transport the balance. Take
care not to bang it against anything as you move it.
2. Check the balance before you start. The balance
pan should be empty and clean, and all masses
should be set on zero. (check to see if they are snugly
placed in their rider position). The balance must be
level. Check the bubble level on your balance. Try to
make it zero, but it is not necessary to have it zeroed
to take accurate measurements.
3. Objects to be placed directly on the balance pan must be clean, dry, and at room temperature.
Now here comes the interesting part: There are 2 parts to this section.
Part 1: Obtaining the mass by placing the nickel directly on the balance:
Part 2: Obtaining the mass using the difference of 2 masses.
Part 1: Place the nickel directly on the balance. Move the riders until it is balanced.
Record the mass of the nickel. You should have 3 decimal places in your final answer.
Mass of the nickel: ___________________________ (don’t forget your units)
Part 2: Place any object on the balance other than the nickel. Use a penny, eraser,
pen, or something else. Move the riders until balanced. Record the mass of the object.
Mass of object: __________________________
Now place the nickel on the balance pan along with the object. Move the riders again
and obtain the combined mass.
Mass of object + nickel: ____________________________
To determine the mass of the nickel, you have to find the difference in the two
measurements above. Show work below. Place your final answer in the space
provided.
Mass of the nickel: _________________________________
Did you get a different mass for the nickel? __________
Which mass is closest to the mass of the nickel using the electronic balance? Was it by
massing the nickel directly on the pan or using the difference of the two measurements
as in part 2? ______________________________________________________
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3. Using a Pipet:
This type of pipet that you are using today is called a volumetric or transfer pipet. This
pipet is used to deliver a single, fixed volume of liquid. Volumetric pipets are calibrated
with only one mark (indicating their maximum capacity) and are available in capacities
ranging from 1 mL to 200 mL.
To use a volumetric pipet:
Solutions and liquids are drawn into a pipet by applying a slight vacuum at the tip of the
pipet, using a rubber suction bulb. Never pipet by mouth!!!!!
Before you begin, obtain a clean, dry 50 mL beaker. Using your quad beam balance,
obtain the mass of the beaker. Record your data below. Place the beaker to the side
and use it again in step # 6.
Mass of clean 50 mL beaker: ____________________ (don’t forget your units)
1. Pour a small amount of liquid to be pipetted into a clean, dry beaker. You will use
distilled water and a 100 mL beaker.
2. Partially squeeze the pipet bulb and slip it onto the wider end of a clean pipet as
shown in the figure (a) above. Make sure that the connection is secure enough to
prevent air leaks.
3. Hold the pipet tip below the solution surface in the beaker. Keep the tip well below
the surface during the pipetting so that air is not drawn into the pipet along with the
solution. Draw a small portion of the solution into the pipet by slowly releasing pressure
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on the bulb. Be careful not to draw liquid into the bulb. Continue until the liquid goes
above the line in the pipet. Lightly rest the pipet on the bottom of the beaker. Today,
you are using water, but later in the year, you will be using other substances. See
figure (b) above.
4. Quickly, but gently, disconnect the bulb from the pipet. If using an adapter, this is
much easier. Place your index finger (not your thumb) on top of the pipet to prevent the
solution from draining out. Remove the pipet from the solution, keeping your index
finger on top. Use a paper towel to wipe the liquid from the outside of the pipet. Rotate
the pipet around allowing some of the solution to fall back into the beaker until the
bottom of the meniscus is level with the line on the pipet. Now hold tightly with your
index finger. See figure (c). Touch the tip of the pipet against the beaker to get rid of
the hanging drop.
5. Now you are ready to deliver the liquid to your final container. Hold tight with your
index finger as you transfer the liquid.
6. Place the tip of the pipet into your pre-massed 50 mL beaker. Hold the tip of the
pipet against the inner wall of the container. (see figure (d).)
7. Lift your index finger from the pipet and allow the solution to drain down the inner wall
of the container. When the flow stops, hold the pipet vertically for 15 more to allow fro
complete draining.
8. Touch the pipet tip to the inner wall of the container to transfer the hanging drop to
the container. Do not attempt to remove the small amount of solution remaining in the
tip of the volumetric pipet. The pipet was calibrated to transfer an exact volume of liquid
excluding the liquid remaining in its tip. See figure (e).
9. Now obtain the mass of the 50 mL beaker plus the 10.00 mL of distilled water.
Record the mass below:
Mass of 50 mL beaker + 10.00 mL distilled water: __________________________
10. Calculate the mass of 10.00 mL of distilled water at room temperature. Record your
answer below:
Mass of 10.00 mL of distilled water at room temperature: _____________________
11. Go to the back of the room by the rescue window and look at the thermometer.
Record the room temperature below:
Room Temperature: ______________________ (remember correct units)
12. Now calculate the density of your water at room temperature. Show all work below.
Record your answer using the units of grams/mL. Box your final answer.
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4. Reading the volume using a graduated cylinder.
Volumetric glassware, unlike other glassware, is calibrated with
markings that are used to determine the specific volume of
liquid in the volumetric glassware.
A liquid in a plastic tube will lie flat, but a liquid in a glass tube
has a curved surface known as a meniscus. In most cases,
the meniscus is concave and the bottom of the curves is read to
determine the volume of a liquid. When reading the volume, always looks straight on to
find the bottom of the meniscus. See figure to the right.
1. Using a 10 mL graduated cylinder, use a 10.00 mL pipet and deliver 10.00 mL of
distilled water into the graduated cylinder.
2. Now read the bottom of the meniscus. Record the volume of the water.
Volume of water:___________________ (don’t forget your units)
Measuring volume by displacement:
-If you have an irregularly shaped object and you would like to know the volume of this
object, you can do so by displacement. To do this:
1. Use a graduated cylinder that has a larger opening than the size of the object.
2. Fill the graduated cylinder ½ full of tap water. Record the volume of water in the
cylinder.
3. Now tilt the graduated cylinder and slowly slide the object into the water. Be careful
not to splash.
4. Now record the volume of the water + object.
5. To determine the volume of the object, all you have to do is subtract the 2 pieces of
data collected.
A. Find the volume of the irregularly shaped rubber stopper that you find at your lab
station. Use the space below to record your data. Make sure you label your data and
use the proper units.
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5. Length:
Using a metric ruler: Record the length of your right index finger’s 2nd digit. Record the
length in millimeters. (You should have 2 decimal places in your answer)
Length of 2nd digit of right index finger: ____________________(don’t forget units)
Using a meter stick determine your height in centimeters. Record your height in meters.
Height:___________________________ (don’t forget units)
6. Mass of yourself:
Use the nurse’s balance to determine your own mass.
1. Make sure the balance is balanced before stepping on the platform.
2. Stand on the platform and then move the riders until you are balanced. Make sure
you are using the metric riders only.
3. Record your mass here: _______________(make sure you include the correct units)
7. Temperature:
Calibrate the thermometer: Thermometers are not always accurate. Each time you use
them for direct measurements, you need to calibrate the instrument. If you are using a
thermometer for a change in temperature, you do not need to calibrate the
thermometer.
1. Use a thermometer and measure the temperature of the room. Record the
temperature below.
-To use a thermometer, handle the glass with care. Never place it directly on the
tabletop, use a paper towel and lay it down on the lab table blocked between 2 objects.
-Never shake down a thermometer. Lab thermometers will go up and down by
themselves.
-Rinse off thermometers with water. Never wash them or dry them. They will air dry on
their own.
-Don’t place your hand near the tip of the thermometer or else it will record your body
temperature, not the room temperature.
-You should have 1 decimal place when reading these thermometers.
Room temperature using an un-calibrated thermometer: _____________ (don’t forget
your units)
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2. To calibrate your thermometer, you need to place the tip into a substance of known
temperature. The easiest thing to do is place it in a beaker full of ice and water. Slowly
stir it around until the liquid in the thermometer stops moving. Then read the
thermometer. Record your temperature below.
-If the thermometer reads 0.0 C, then you have an accurate thermometer and you don’t
have to correct your temperature readings.
-If the thermometer reads below or above zero, then you have subtract or add that
amount to all of your readings used with this thermometer.
Temperature of the ice-water mixture: __________ (include proper units)
3. Now calculate the true temperature of the room. Show work below and then place
your final answer on the line below.
Room Temperature: ____________________
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Name:_______________________________
Date:__________ Block: ________
Pre-lab #3 Reading Instruments to the correct number of significant figures.
When reading instruments, you need to record the reading to the correct number of
significant figures. What this means is that you are to record your answers so that you
record all numbers you are sure
of in the measurement, plus you
are allowed one guess. If the
measurement appears to be on a
line, then the last figure written
should be a zero.
1. To the right are sections of
graduated cylinders with water in
them. The units for all of the
measurements are milliliters.
2. Read each graduated cylinder
and record the measurement to
the correct number of significant
figures. Always state the figures
you are sure of, plus one guess.
3. Make sure you record your
measurements using the proper
units.
4. Each of the graduated
cylinders may be different from
each other.
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Reading a balance: Below are 2 different types of balances. Record the mass for
each balance to the proper number of significant figures. Make sure you use grams for
your units.
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