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Austin Peay State University Department of Chemistry
CHEM 1111
Measurement & Density
Introduction
Measurement is a regular part of life. For example, weight, height, and blood pressure are routinely measured in
a doctorÃ¢â‚¬â„¢s office. In the kitchen, ingredients for a recipe must be measured. Devices such as scales and measuring cups
were developed to make these measurements.
In chemistry, solutions are often used and transferred from one container to another. In some cases, it is
important to know the amount of liquid transferred with certainty, especially when performing a quantitative analysis.
Quantitative analysis is the determination of the concentration or amount of substance in a particular sample. The
certainty of a measurement is determined by looking at both the accuracy and precision of a set of measurements. While
ideal measurements should be both accurate and precise, measurements made in the lab are more often either accurate
but not precise or precise but not accurate.
Accuracy is a measure of how close a data point is to an accepted (true) value. If multiple measurements are
made of a value, then the accuracy is determined by taking the average
value and comparing it to the accepted value. The absolute error is the
difference between the accepted value and an individual measurement
% error =
measured Ã¢Ë†â€™ accepted
accepted
x 100
or average. The relative error is the absolute error divided by the accepted value. The percentage error is the relative
error multiplied by 100 %. Absolute error, relative error and percentage error are all measures of accuracy. The
percentage error is often expressed as a positive number, regardless of whether the measured value is larger or smaller
than the accepted value.
The term Ã¢â‚¬Å“precisionÃ¢â‚¬Â may be applied to either a single measurement or a group of measurements. Generally the
precision of a single measurement is simply a measure of the number of significant figures that can be expressed. Thus, a
ruler calibrated to the nearest millimeter would be more precise than a ruler calibrated to the nearest centimeter. To
express the precision of a single measurement quantitatively, the proper number of significant figures must be used.
Precision of a group of points is a measure of how close each measurement is to the others. Another way of considering
precision is to look at the range of the values; that is the difference between the highest and lowest measured values. The
smaller this range, the more precise the measurements are. In both of these definitions of precision, notice the
measurements are never compared to the accepted measured value.
When using an instrument with a digital display, write down the measurement value with the same number of
significant figures as the digital display allows. Our top-loader balances have a precision of + 0.001 g. If a mass is
displayed as 24.567 grams, this means that all but the last digit are known with certainty; last digit (7) has some degree of
uncertainty. The uncertainty in the last digit is usually assumed to be +1. However, if the balance is fluctuating in the last
two digits, then both of those numbers have error associated with them.
When reading a burette or other calibrated analog scale, the measurement should be estimated to one digit
beyond what the markings allow. Therefore, if a burette is calibrated to the nearest 0.1 mL, then the volume measurement
should be estimated to the nearest 0.01 mL. For example, if a volume measurements 11.74 mL, the 11.7 mL is known
with certainty while the 0.04 mL was estimated by the person reading the burette. Precision is often related to the person
making the measurement; very seldom do two different people make the exact same measurement every time. However,
as long as the measurement is made in a consistent manner, the precision should not be significantly affected.
In this experiment, the density of water will be measured using a burette, a graduated cylinder, a beaker and a
volumetric pipette. Based on the results, the most accurate measuring device will be determined.
Revision S20
Page 1 of 6
Austin Peay State University Department of Chemistry
CHEM 1111
Measurement & Density
Procedure
Record all measurements and unknown numbers (if given) on your data sheets. Use the proper number of significant
figures for all measurements.
Part A: Determining the Density of Water Using a Burette
A1. Obtain a burette, and fill it with deionized water using a beaker and funnel. Let the water drain through the
burette until the tip is full (the initial volume reading does NOT have to be 0.00 mL). Observe and sketch the
meniscus. Remember that measurements must always be made at the bottom of the meniscus for aqueous
solutions in glass.
A2. Obtain a 50 mL beaker. Measure and record its mass.
A3. Read and record the initial water level in the burette. Deliver approximately 15 mL of water to the preweighed beaker from the burette and read and record the final water level in the burette.
A4. Measure the mass of the beaker and water.
A5. Empty and dry the beaker.
A6. Repeat steps A2 – A5 two more times.
? Why is this process performed three times?
A7. Measure the temperature of the water.
? Why is knowing the temperature of the water important?
Part B: Determining the Density of Water Using a Graduated Cylinder
B1. Obtain a dry 100 mL graduated cylinder.
B2. Measure the mass of the empty 100-mL graduated cylinder.
B3. Add approximately 22.0 mL of deionized water to the graduated cylinder. Record the exact volume of water in
B4. Measure the mass of the water and 100-mL graduated cylinder.
B5. Empty and completely dry the graduated cylinder.
B6. Repeat steps B2 – B5 two more times.
B7. Measure the temperature of the water.
Part C: Determining the Density of Water Using a 50 mL Beaker
C1. Weigh a clean, dry 50 mL beaker that has graduation marks on it. Record its mass.
C2. Add approximately 20. mL of deionized water to the beaker. Record the exact volume of water in the beaker.
C3. Measure and record the mass of the filled beaker.
C4. Empty and dry the beaker.
C5. Repeat steps C1 – C4 two more times.
C6. Measure the temperature of the water.
Revision S20
Page 2 of 6
Austin Peay State University Department of Chemistry
CHEM 1111
Measurement & Density
Part D: Determining the Density of Water Using a 10 mL Volumetric Pipette
D1. Obtain a 50 mL beaker, measure and record its mass.
D2. Use a pipette bulb to fill the volumetric pipette to its calibration mark. The calibration mark corresponds to
10.00 mL of water being delivered from the pipette. It already takes into account that there will be a small
amount of water left in the tip, so that is not an experimental error. Empty this volume of water into the
weighed 50-mL beaker.
D3. Measure and record the mass of the beaker and water.
D4. Empty and dry the beaker.
D5. Repeat steps D1 – D4 two more times.
D6. Measure the temperature of the water.
?
Why was the same procedure performed using 4 different pieces of glassware?
?
Why was water used in this experiment?
?
What is the difference between an extensive and an intensive property of a substance? State whether
mass, volume and density are extensive or intensive properties.
?
Describe two things that you learned in this lab.
Calculations
Put the results of all calculations in your lab notebook.
On a separate lab notebook page, show your calculation work for one trial of calculations A1, A2, A3, A4, A5 and A7.
A. Burette
A1. Determine the volume of water delivered by the burette in each trial by subtracting the burette readings
A2. Determine the mass of water delivered by the burette in each trial by subtracting the mass readings.
A3. For each trial calculate the experimental density of water using the mass of water delivered and the volume of
water delivered.
A4. Calculate the average density of the three trials.
A5. Calculate the standard deviation for the three trials.
A6. Using the measured temperature of the water and the reference density table, determine the accepted value
for the density of water.
**EXTRA CREDIT: Use linear interpolation to determine the density of water using the temperature measurement
to the nearest tenth of a degree.
A7. Calculate the percent error using the experimental and accepted values for the density of water.
Revision S20
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Austin Peay State University Department of Chemistry
CHEM 1111
Measurement & Density
B1. Determine the mass of water in each trial by subtracting the mass readings.
B2. For each trial calculate the experimental density of water using the mass of water and the volume of water.
B3. Calculate the average density of the three trials.
B4. Calculate the standard deviation for the three trials.
B5. Using the measured temperature of the water and the reference density table, determine the accepted value
for the density of water.
**EXTRA CREDIT: Use linear interpolation to determine the density of water using the temperature measurement
to the nearest tenth of a degree.
B6. Calculate the percent error using the experimental and accepted values for the density of water.
C. Beaker
C1. Determine the mass of water in each trial by subtracting the mass readings.
C2. For each trial calculate the experimental density of water using the mass of water delivered and the volume of
water delivered.
C3. Calculate the average density of the three trials.
C4. Calculate the standard deviation for the three trials.
C5. Using the measured temperature of the water and the reference density table, determine the accepted value
for the density of water.
**EXTRA CREDIT: Use linear interpolation to determine the density of water using the temperature measurement
to the nearest tenth of a degree.
C6. Calculate the percent error using the experimental and accepted values for the density of water.
D. Volumetric Pipette
D1. Determine the mass of water in each trial by subtracting
Density of Water as a Function of
Temperature
o
T ( C)
Density (g/mL)
D2. For each trial calculate the experimental density of water
20
0.9982071
using the mass of water delivered and the volume of
21
0.9979955
water delivered.
22
0.9977735
D3. Calculate the average density of the three trials.
23
0.9975415
D4. Calculate the standard deviation for the three trials.
24
0.9972995
D5. Using the measured temperature of the water and the
25
0.9970479
reference density table, determine the accepted value for
26
0.9967867
the density of water.
27
0.9965162
28
0.9969748
29
0.9962365
30
0.9956502
**EXTRA CREDIT: Use linear interpolation to determine the
density of water using the temperature measurement to
the nearest tenth of a degree.
D6. Calculate the percent error using the experimental and
accepted values for the density of water.
Revision S20
Page 4 of 6
Austin Peay State University Department of Chemistry
CHEM 1111
Measurement & Density
Data Sheet
Make these data tables in your lab notebook.
Enter data and calculated values into the data tables in your laboratory notebook.
Make sure to label all values with units!
Part A: Determining the Density of Water Using a Burette
Trial 1
Trial 2
Trial 3
Final water level in burette
Initial water level in burette
Volume of water delivered
Mass of beaker and water
Mass of empty beaker
Mass of water delivered
Experimental density of water
Average experimental density of
water
Standard Deviation
Temperature of water
Accepted density of water from table
% Error
Part B: Determining the Density of Water Using a Graduated Cylinder
Trial 1
Trial 2
Trial 3
Measured volume of water delivered
water
Mass of water delivered
Experimental density of water
Average experimental density
Standard Deviation
Temperature of water
Accepted density of water from table
% Error
Revision S20
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Austin Peay State University Department of Chemistry
CHEM 1111
Measurement & Density
Part C: Determining the Density of Water Using a 50 mL Beaker
Trial 1
Trial 2
Trial 3
Trial 2
Trial 3
Measured volume of water delivered
Mass of beaker and water
Mass of empty beaker
Mass of water delivered
Experimental density of water
Average experimental density
Standard Deviation
Temperature of water
Accepted density of water from table
% Error
Part D: Determining the Density of Water Using a Volumetric Pipette
Trial 1
Measured volume of water delivered
Mass of beaker and water
Mass of empty beaker
Mass of water delivered
Experimental density of water
Average experimental density
Standard Deviation
Temperature of water
Accepted density of water from table
% Error
Revision S20
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