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Glassware Lab Report
2 September 2016
CHM 113, Friday 8:30-10:20
Glassware is the most common tool used in a laboratory. With different experiments being conducted, there are various kinds of glassware to accommodate their needs. For example, there is the buret, which is usually used in titration because of its incredible accuracy. Not all glassware is as accurate and precise as the buret. Accuracy refers to how close a certain measurement gets to the accepted value, while precision refers to how close and how often a certain measurement weighs out to its calculated value. Because of this, we decided to attempt to understand the differences/similarities between each glasswares’ precision and accuracy. In order to do this, we had to measure the mass of water and divide it by its volume (g/mL) to get the density of the water in the different glassware. By conducting three trials of each, we were able to get an average density of each glassware.
For part one of this experiment, obtain a 50 milliliter (mL) beaker, a 100 mL beaker, a 125 mL Erlenmeyer flask, a 50 mL buret, a 10 mL graduated cylinder, a plastic pipette, weighing boat, goggles, and an Electronic balance. For the second part of this experiment, obtain a small quantity of sand.
Before beginning this experiment, the temperature of the distilled water to be used, was measured. First, a beaker was acquired, and using a thermometer, the temperature was recorded.
To begin, a 50 mL beaker was obtained and the scale used was set to zero using the tare button. The beaker was weighed and the mass was recorded. Approximately 20 mLs of water was added to the beaker and the mass was recorded the same way again. The beaker was emptied and the above procedure was repeated two more times and then recorded. The procedures were repeated for the 100 mL beaker with approximately 50 mLs of water and the results were recorded after each of the three trials. The scale used between the multiple trials and beakers was the same. Next, a 125 mL Erlenmeyer beaker was obtained and again, the scale was zeroed by pressing the tare button. The flask was weighed, and the mass was recorded. The flask was filled with approximately 75 mL of water and the weight was recorded in the same manner as the masses for the water in the beakers were recorded. This was repeated two additional times and recorded. Third, a 10 mL graduated cylinder was massed as had been previously done with other glassware. The graduated cylinder was filled with 5mL of water and massed. This was repeated two additional times. In testing the 50 mL buret, mass could not be obtained using a scale. Therefore, a 100 mL beaker was used to measure the mass instead simply weighing the glassware. 40 mL of water were poured into the buret using a funnel. Then 10 mL of water were dispensed into the beaker and the beaker was weighed. The beaker was emptied and the procedure was repeated two more times. Lastly, a weighing plate was obtained and placed on the same scale. The scale was zeroed and sand was adjusted on the plate until one gram of sand was obtained in the tray. The mass was recorded and the procedure was repeated two more times.
Table 1: Determining the Precision and Accuracy of Various Glassware
The table above expresses the average density of the three trials of each type of glassware and the percent error.
Density Sample Calculation (Buret Trial): 11.38g10.00mL= 1.14 g/mL
Percent Error Sample Calculation (Buret Trial):1.14 g/mL -1.00 g/mL1.00 g/mL*100% = 14.00%
The purpose of this experiment was to determine the most precise and accurate glassware in measuring volume to find density. From Table 1, the 125 mL erlenmeyer flask was the most accurate in this experiment with a 0.19% density error, and the following from least percent error to highest percent error went: 10 mL graduated cylinder, 50 mL beaker, buret, 100 mL beaker. This ranking was determined by the percent error calculation that required the accepted value of the density of water. Significant figures are important in this lab due to the constant measuring of water in each trial. This ensures that the accuracy of each value is all equal in degree and measurement. Finding the percent error is important because accuracy is essential when measuring values because it determines how close the measured values are to the true value. Independent of accuracy, is precision, which measures the proximity of the measured values to each other. The differing percent errors of each type of glassware could have been attributed to a variety of factors, including measurement errors. The balance’s lag time may have been a factor because the readings on the balance would stabilize by shifting between a range of numbers around the measured value, in which one number had to be deduced. Another factor of error may have also included the skewed perception and reading of the measured values of water, due to the misalignment of the measurer’s line of sight to the meniscus line. The experiment could have been improved by exacting the measurements of water with the transfer or removal of water or using the same volumes of water for each trial. If one wanted to obtain a measurement of 38 mL of water, the best glassware type to use would be the erlenmeyer flask because it can first off, hold that much liquid, and it had the least percent error in the experiment, hence the greatest accuracy. If one wanted to obtain a measurement of 38.5 mL of water, the best type of glassware to use would be the erlenmeyer flask as well because again, of its high accuracy of measurement. Since the erlenmeyer flask is marked in increments of 25 mL, one could be more precise by using another glassware type, such as a biuret that has the smaller mL increments, in order to fill the 125 mL erlenmeyer flask.
In any lab environment, glassware is a crucial element, providing not only a medium to transport various chemicals, but a way to accurately measure its contents volume. However, different types of glassware have different degrees of accuracy. Our group’s goal was to determine which glassware would have the least percent error in measuring the volume of a known volume of water. Based on the results, it has been determined that the erlenmeyer flask has the least percent error, and therefore, is the most accurate method of determining volume of our available glassware
Bauer, R., Birk, J., Sawyer, D. Laboratory Inquiry in Chemistry, 3rd ed.; Brooks/Cole Cengage
Learning: Belmont, 2009 Navarrete, C. Electronic Resources Review 2000.dditional times. In testing the 50 mL buret, mass could not be obtained using a scale. Therefore, a 100 mL beaker was used to measure the mass instead simply weighing the glassware. 40 mL of water were poured into the buret using a funnel. Then 10 mL of water were dispensed into the beaker and the beaker was weighed. The beaker was emptied and the procedure was repeated two more times. Lastly, a weighing plate was obtained and placed on the same scale. The scale was zeroed and sand was adjusted on the plate until one gram of sand was obtained in the tray. The mass was recorded and the procedure was repeated two more times.
The purpose of this experiment was to determine the most precise and accurate glassware in measuring volume to find density. From Table 1, the 125 mL erlenmeyer flask was the most accurate in this experiment with a 0.19% density error, and the following from least percent error to highest percent error went: 10 mL graduated cylinder, 50 mL beaker, buret, 100 mL beaker. This ranking was determined by th