How is Lab Glassware Used?

Intro:
The concept of the lab, “How is Glassware Used?” was to familiarize ourselves with the different kinds of laboratory glassware like the buret, Erlenmeyer flask, beaker, and graduated cylinder. According to Dartmouth each glassware functions best in different settings; A buret is used to deliver solution in precisely-measured, variable volumes,1 Erlenmeyer flasks and beakers are used for mixing, transporting, and reacting, but not for accurate measurements, and graduated cylinders are useful for measuring liquid volumes but are for general purpose use, not for quantitative analysis.2 Essentially each glassware either holds certain volumes or delivers certain volumes.
The main purpose of the experiment was to see which glassware is both the most precise and the most accurate through testing them and calculating which one has the lowest average percent error. Accuracy is how close the measured value is to the true value of what is being measured. To assure accurate measurements were made, special attention was kept on significant figures in the measurements. Significant figures are numbers that carry meaning in the measurement. Accuracy can be said to be “good” or “bad”, however this is qualitative and doesn’t give a decent sense of how accurate something really is, so a quantitative way of stating accuracy was devised to determine how accurate something is. The quantitative measure of accuracy is called percent error which calculates in a percent how much the measured value deviates from the true value. Precision then, is how close repeated measurements are to each other. Precision can also be qualitatively described with “high” or “low” precision.
The more precise and accurate the equipment in measuring then the lower the percent error in the final calculation. To determine how accurate and precise each piece of glassware is, each piece was filled to a recorded volume with water at a recorded temperature and then the mass of the water was found. Using this information the density of the water was calculated and the theoretical density of the water was found for water at its recorded temperature. Density is the ratio of volume to mass and density will increase if either mass or volume increase. Since density is the ratio of volume to mass it was calculated with the volume divided by mass. Using the calculated density of water and the theoretical density of water the percent error was dzetermined. The objective was to determine the relationship between percent error, and measurement accuracy as well as to use significant figures to keep the data organized.
Procedure:
Part one of the experiment started with approximately 300mL of water being obtained in a 600mL beaker. This water was used for the entirety of the experiment. A thermometer was placed in the water and the temperature was recorded after the temperature stayed consistent. Obtaining an empty and dry 50mL beaker its mass was taken and recorded. Once its empty mass was recorded the beaker was filled with 40mL of water from the 300mL gathered at the start and massed again. The new mass was recorded as well. The mass of the water was calculated by subtracting the weight of the beaker empty beaker from the weight of the beaker with water. Using the mass of the water and the volume of water from the 50mL beaker the density of the water was calculated. With the temperature of the water that was taken at the beginning the theoretical density of water at that temperature was found and then using the theoretical density and the experimental density the percent error of the beaker was found. Once the calculation were done the water in the 50mL beaker was replaced back into the 600mL beaker. After calculating the percent error part one of the experiment was redone two more times and using the three trials the average density and percent error were calculated. The above procedure was repeated with a 125mL Erlenmeyer flask using three trials. Part two of the experiment began with obtaining a 50mL burette and setting it up with a ring stand and clamp. Once the Burette was set up an empty and dry 100mL beaker was gathered and massed and the mass recorded. The temperature of the water in the 600mL beaker was again taken and recorded. With the mass of the beaker and the temperature of the water recorded the burette had 100mL of water from the 600mL beaker carefully measured into the burette. The 100mL beaker was placed underneath the burette and the burettes contents were emptied into the beaker. Once all of the water had left the burette and filled the beaker the beaker was again massed and had its mass recorded. The mass of the water was calculated by subtracting the weight of the beaker empty beaker from the weight of the beaker with water. Using the mass of the water and the volume of water from the 50mL beaker the density of the water was calculated. With the temperature of the water that was taken at the beginning the theoretical density of water at that temperature was found and then using the theoretical density and the experimental density the percent error of the burette was found. Once the calculation were done the water in the 100mL beaker was replaced back into the 600mL beaker. After calculating the percent error part two of the experiment was redone two more times and using the three trials the average density and percent error were calculated. Part three of the experiment started with obtaining an empty and dry 10mL graduated cylinder and massing and recording its mass. Once the mass was recorded the temperature of the water in the 600mL beaker was taken and recorded. After the temperature was recorded 1ml of water was added to the graduated cylinder using a disposable plastic pipet and each drop from the pipet was counted. Once the graduated cylinder was filled with 1mL of water the graduated cylinder was massed again and the new mass was recorded. The mass of the water was calculated by subtracting the weight of the empty graduated cylinder from the weight of the graduated cylinder with water. Using the mass of the water and the volume of water from the graduated cylinder the density of the water was calculated. With the temperature of the water that was taken at the beginning the theoretical density of water at that temperature was found and then using the theoretical density and the experimental density the percent error of the burette was found. Once the calculation were done the water in the 10mL graduated cylinder was replaced back into the 600mL beaker. After calculating the percent error part three of the experiment was redone two more times and using the three trials the average density and percent error were calculated. The final part of the experiment started with obtaining an empty and dry 50mL beaker. It was filled with 4 scoops of sand using a scoopula. Taking the beaker to the electric scales a weighing boat was placed onto a scale and the Tare button was hit. Once the Tare button was hit one gram of sand was measured out using the scale. Once the weight was as close to one gram as it could be the mass was recorded. After the mass was recorded the weighing was redone two more times. Using the three trials the average mass of the sand weighed was found.

Results:
Part One
Average Density of 50mL Beaker of 50mL of Distilled Water
Temperature of water (ºC) 15.9 ºC
Theoretical density of water at Temperature of water. (g/mL) 0.9989460g/mL
Mass of empty 50mL beaker (g) 30.232

Trial Mass of 50mL beaker with water (g) Mass of water (g)
(mass of Beaker w/ water – empty beaker) Volume of water (mL) Density of water (g/mL)
(mass of water/volume of water) % error
[(Theoretical value-experimental value)/theoretical value]*100
1 68.235g. 38.003g. 40mL. .95008g/mL 4.8923%
2 68.500g. 38.268g. 40mL. .95670g/mL 4.2291%
3 68.561g. 38.329g. 40mL. .95823g/mL 4.0764% Average Density (g/mL) .95500g/mL
Average % error 4.3993%

Average Density of 125mL Erlenmeyer flask of 50mL of Distilled Water
Temperature of water (ºC) 16.2 ºC
Theoretical density of water at Temperature of water. (g/mL) 0.9989460g/mL
Mass of empty Erlenmeyer flask(g) 90.152

Trial Mass of 125mL Erlenmeyer flask with water (g) Mass of water (g)
(mass of flask w/ water – empty flask) Volume of water (mL) Density of water (g/mL)
(mass of water/volume of water) % error
[(Theoretical value-experimental value)/theoretical value]*100
1 136.326g. 46.074g. 50mL .92148g/mL 7.7548%
2 136.776g. 46.624g. 50mL .93248g/mL 6.6536%
3 135.807g. 45.655g. 50mL .91310g/mL 8.5937% Average Density (g/mL) .92235g/mL
Average % error 7.6674%

Part two
Average Density of 50mL Burette of 50mL of Distilled Water
Temperature of water (ºC) 16.8 ºC
Theoretical density of water at Temperature of water. (g/mL) 0.9987779g/mL
Mass of empty 100mL beaker (g) 50.900g.

Trial Mass of 100mL beaker with water (g) Mass of water (g)
(mass of Beaker w/ water – empty beaker) Volume of water (mL) Density of water (g/mL)
(mass of water/volume of water) % error
[(Theoretical value-experimental value)/theoretical value]*100
1 102.908g. 52.008g. 50mL. 1.0402g/mL 4.1473%
2 102.539g. 51.639g, 50mL. 1.0328g/mL 3.4064%
3 102.433g. 51.533g. 50mL. 1.0307g/mL 3.1961% Average Density (g/mL) 3.1037g/mL
Average % error 3.5833%

Part three
Average Density of 10mL graduated cylinder of 1mL of distilled water
Temperature of water (ºC) 17.0 ºC
Theoretical density of water at Temperature of water. (g/mL) 0.9987779g/mL
Mass of empty 10mL graduated cylinder (g) 27.942g.

Trial Mass of 10mL graduated cylinder with water (g) Mass of water (g)
(mass of cylinder w/ water – empty cylinder) Volume of water (mL) Density of water (g/mL)
(mass of water/volume of water) % error
[(Theoretical value-experimental value)/theoretical value]*100 Number of drops to make 1mL
1 28.944g. 1.0020g. 1mL. 1.0020g/mL .33260% 28
2 28.955g. 1.0130g. 1mL. 1.0130g/mL 1.4240% 27
3 29.070g. 1.1280g. 1mL. 1.1280g/mL 12.938% 29 Average Density (g/mL) 1.0477g/mL
Average % error 4.8949%

Part four
Determine the mass of sand with Taring

Trials Mass of sand (g)
1 .993g.
2 1.018g.
3 1.022g.

Average mass of sand (g) 1.011g.

Sample Calculation
Using data from Table #1, Trial #1.
Density(D)=(Mass(M))/(Volume(V))
Percent Error= (|Theoretical value-experimental value|)/(Theoretical value)×100
Mass=38.003g
Volume=40mL
Theoretical Density at 17 °C= .998946 g/mL
D=38.003g/40mL=.95008 g/mL
Percent Error= (|.998946-.95008|)/.998946×100=4.8923%

Discussion:
The purpose of this experiment was to determine the most accurate and/or precise piece of glassware (50 mL beaker, 125 mL Erlenmeyer flask, 50 mL burette, or 10 mL graduated cylinder) through the calculation of average percent errors. Another objective of the experiment was to familiarize oneself with the TARE button on the electronic balance by massing out 1 gram of sand.
After conducting the experiment, the results show that the order of glassware from most accurate to least accurate is as follows: 50 mL burette at 3.5833 average percent error, 50 mL beaker at 4.3993 average percent error, 10 mL graduated cylinder at 4.8949 average percent error, and 125 mL Erlenmeyer flask at 7.6674 average percent error. Accuracy deals with how close the results are to the true value. The most precise to least precise glassware is as follows: 50 mL beaker with a range (highest percent error minus lowest percent error) of 0.8159 between the three calculated percent errors, 50 mL burette with a range of 0.9512 between the three calculated percent errors, 125 mL Erlenmeyer flask with a range of 1.9401 between the three calculated percent errors, and 10 mL graduated cylinder with a range of 12.615 between the three calculated percent errors. Precision deals with how close the calculated results are to each other. The significant figures were carefully calculated, considering that they play an important role in determining accuracy and precision. The difference between two trials may come down to the thousandth of a decimal, thus it is imperative that the scientist pays attention to the proper number of significant figures he/she includes in the calculations.
Sources of error that may have skewed the data included: reading the meniscus incorrectly, reading the thermometer incorrectly, and not wiping excess water off of the glassware before massing it. If the bottom of the meniscus curve was not used as the indicator of the volume of water in the glassware, then the accuracy of the data was compromised. If the thermometer was not read and recorded frequently, then the average density of the water at that temperature was not properly factored into the calculations, thus compromising the accuracy of the data. Lastly, if excess water was not removed from the outside of the glassware before massing it, then those water droplets affect the overall mass, thus interfering with the accuracy of the data since they were not factored into the recorded volume of water in the glassware.
The percent error in the densities could have been due to improper recording of the water temperature, which directly affected the recorded actual density of the water (universally known values found in many sources). The percent error in densities could also have been directly related to the possibility that excess water droplets were not removed from the glassware before massing, negatively affecting the accuracy of the recorded mass which was then used to calculate the density of the water. Lastly, percent error in the densities could have been due to improper reading of the meniscus, thus directly affecting the numbers used to calculate the density of the water. The volume measurements did not vary. According to the measurements, the volume of water in each glassware was consistent for all three trials.
With the information above in mind, one could do a few things differently to improve the results of the experiment. First, the glassware must be wiped off before massing so that excess droplets do not affect the recorded mass of the measured volume of water, in turn interrupting the calculated density of the water and creating a higher percent error. Next, the thermometer must be read correctly so that a proper “actual density” of the water at the recorded temperature is used in the calculation of the percent error. Lastly, the meniscus must be read properly, so that the volume measurements are exact, ensuring proper measurement of not only the volume but the mass of the water as well, for these measurements affect the calculated density of the water as well as the percent error.
If one was to measure out 38 mL of water, the 50 mL beaker would suffice, because it has an average percent error of 4.3993, which is relatively low, and since the measurement does not include decimals, the selected glassware does not require those smaller increments. Now if one was to measure 38.50 mL of water, the 50 mL burette would be the best instrument, seeing that it is most accurate, with an average percent error of 3.5833. This particular piece of glassware is best for measuring out a volume of water to the decimal place.

Conclusion: The goals of this lab were to use the calculated average percent errors of the various glassware to determine which is most accurate and/or precise in measuring the volume of a liquid, and to use the TARE button on the electronic balance to measure out 1 gram of sand. Both goals were adequately met, resulting in a fairly successful investigation.
In conclusion, should a scientist wish to accurately measure the volume of a liquid he/she should utilize the 50 mL burette, since it has the lowest average percent error of 3.5833%. Should the scientist wish to precisely measure the volume of a liquid, he/she should utilize the 50 mL beaker, since it has the lowest range of 0.8159 between the three calculated percent errors.

Works Cited Dartmouth.edu,. ChemLab - Glassware - Burets https://www.dartmouth.edu/~chemlab/techniques/buret.html (accessed Sep 16, 2015). Dartmouth.edu,. ChemLab - Glassware - Flasks, Beakers, & Graduated Cylinders https://www.dartmouth.edu/~chemlab/techniques/flasks.html (accessed Sep 16, 2015).