Name: _____________________________________________ Date: __________
Accuracy, Precision, and Measurements
Introduction
It would be hard to overstate the importance of taking proper
measurements in the chemistry laboratory. The goal of most of the
experiments that you will perform this year is to obtain accurate, precise
data. You will use your data to perform calculations and formulate
conclusions about chemical principles. Obviously, these calculations
and conclusions can only be as accurate as the measurements that they
are based on. For this reason, you must take each measurement to the
maximum accuracy allowed by the instrument you use. The accuracy of
each measurement is limited by two things: the limitations of the
instrument and the care of the experimenter. You must also make sure
that you don’t accidentally claim that a measurement or calculation is
more accurate than it actually is.
Purpose
The objectives of this lab are to:
 Measure each physical quantity to the maximum accuracy allowed
by the appropriate instrument.
 Record measurements and calculations with the appropriate units
from the international system of units.
 Calculate volumes and densities to the appropriate number of
significant digits.
Materials
electronic balance
50 mL buret
distilled water
buret clamp
100 mL graduated cylinder
150 mL beaker
ring stand
Procedure
Measuring Volume Using a Graduated Cylinder
1. Determine the mass of a 100 mL graduated cylinder and record the
value in Table 1. Remember to include appropriate units and an
estimation digit for the measurement.
2. Obtain about 100 mL of distilled water in a clean Erlenmeyer flask.
Determine and record the temperature of the distilled water.
3. Fill the graduated cylinder with distilled water so that the meniscus of
the water level lines up with the 25 mL calibration mark of the
cylinder.
4. Dry the outside of the graduated cylinder.
5. Determine the mass of the graduated cylinder and water and record
the value in Table 1. Remember to include appropriate units and an
estimation digit for the measurement.
6. Determine the actual amount of water placed in the graduated
cylinder and record the value in Table 1. Remember to include
appropriate units and an estimation digit for the measurement.
Measuring Volume with a Beaker
1. Clean and dry a 150 mL beaker.
2. Determine the mass of the beaker and record the value in Table 2.
Remember to include appropriate units and an estimation digit for the
measurement.
3. Obtain about 100 mL of distilled water in a clean Erlenmeyer flask.
Determine and record the temperature of the distilled water.
4. Fill the beaker with distilled water to the 50 mL calibration mark of
the beaker.
5. Dry the outside of the beaker.
6. Determine the mass of the beaker and water and record the value in
Table 2. Remember to include appropriate units and an estimation
digit for the measurement.
7. Record the amount of water placed in the beaker. Remember to
include appropriate units and an estimation digit for the
measurement.
Measuring Volume with a Buret
1. Clean and dry a 150 mL beaker.
2. Determine the mass of the beaker and record the value in Table 3.
Remember to include appropriate units and an estimation digit for the
measurement.
3. Determine and record the initial liquid level in the buret. Remember
to include appropriate units and an estimation digit for the
measurement.
4. Place the 150 mL beaker under the stopcock of the buret.
5. Open the stopcock of the buret and run water into the beaker until
approximately 25 mL of water has been dispensed.
6. Determine and record the final liquid level in the buret. Remember to
include appropriate units and an estimation digit for the
measurement.
7. Determine and record the mass of the beaker and water. Remember
to include appropriate units and an estimation digit for the
measurement.
8. Determine and record the temperature of water in the beaker.
Data Analysis
For each problem below, show your work in your laboratory notebook.
Record your answer in the data table. Remember to include appropriate
units and the correct number of significant figures with your answer.
1. Calculate the mass of water in the graduated cylinder. Record your
answer in Table 1.
2. Using the mass of water and the density of water at the measured
temperature, calculate the volume of water actually in the graduated
cylinder. Record this answer in Table 1. Remember,
Density = mass
volume
3. Calculate the difference in the observed volume and the calculated
volume for the graduated cylinder. Record your answer in Table 1.
4. Calculate the mass of water in the 150 mL beaker. Record your
answer in Table 2.
5. Calculate the actual volume of water in the 150 mL beaker. Record
your answer in Table 2.
6. Calculate the difference in the observed volume and the calculated
volume for the graduated cylinder. Record your answer in Table 2.
7. Calculate the mass of water transferred from the buret. Record your
answer in Table 3.
8. Calculate the volume of water transferred from the buret. Record your
answer in Table 3.
9. Calculate the actual volume of water transferred from the buret.
Record your answer in Table 3.
10. Calculate the difference in the observed volume and the calculated
volume for the buret. Record your answer in Table 3.
Conclusion
1. Based on the data collected in this experiment, which piece of
volumetric glassware is the most accurate, the graduated cylinder, the
beaker, or the buret? Use data you collected in this lab to justify
your answer.
2. Which piece of volumetric glassware allowed you to make the most
precise measurements? How can you tell?
Table 1. Determining the Accuracy of a Graduated Cylinder
Mass of empty 100 mL graduated
cylinder
Mass of cylinder + water sample
Mass of water in cylinder
Observed volume of water in
cylinder
Temperature of water in cylinder
Density of water at this
temperature
Calculated volume of water
transferred
Difference between observed and
calculated volume
Table 2. Determining the Accuracy of a Beaker
Mass of empty 150 mL beaker
Mass of beaker + water sample
Mass of water in beaker
Observed volume of water in beaker
Temperature of water in beaker
Density of water at this
temperature
Calculated volume of water
transferred
Difference between observed and
calculated volume
Table 3. Determining the Accuracy of a Buret
Mass of empty 150 mL beaker
Initial liquid level in buret
Final liquid level in buret
Volume of liquid transferred
Mass of beaker + water sample
Mass of water in beaker
Temperature of water in beaker
Density of water at this
temperature
Calculated volume of water
transferred
Difference between observed and
calculated volume