Lab report 2 CHM 113 - Testing the Precision of Various...

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Testing the Precision of Various GlasswareChris Bautista, Brittany Been, Michael DemangoneSeptember 8, 2016 Th @ 8:30 amJackie Garcell, CHM 113 Section 23
IntroductionGlassware is distinguished between glassware that hold certain volumes and those thatdeliver specific volumes, meaning some are designed with less precise measurement capabilitiesthan others. The glassware designed to hold certain volumes, such as beakers and Erlenmeyerflasks, have less labeling for measurements and have larger increments between volumes, such as25 mL per dash mark. Meanwhile, more precise glassware such as graduated cylinders andvolumetric burettes are designed with significantly more ability to measure, and have dash marksthat can measure within 1.0 and 0.1 mL. When it comes to the accuracy of glassware, accuracy isdefined by how close a measurement is to the true value (Helmenstine). On the contrary,precision is defined by the consistency of repeated measurements, and how close thosemeasurements are to one another (Helmenstine). For instance, if one throws a dart and hits thecenter of the target, that measurement is highly accurate because it’s close to the desired value.When talking about precision, if one throws a dart at the target four times and hits them allwithin an inch of each other, but they’re all off target, that measurement is highly precise.This is where significant figures come into play. Significant figures are used in chemistryto record a certain number of digits and indicate the precision of that measurement with respectto the device that was used. The number of significant figures in a measurement is for the benefitof a reader or another research trying to replicate the experiment, because it gives the indicationof what digits were certain, and which ones were uncertain and were an estimate whilemeasuring. As every measurement made is uncertain, it’s essential to only use those that areimportant (Pinkerton and Chester). Not all digits in a measurement have significance and shouldbe written down (Pinkerton and Chester). How one determines the number of significant figures
in a digit is based on the measuring ability of the device being used. For instance, if one is usinga 10. mL graduated cylinder that has marks for every 1.0 mL, and were to measure a volume, onecould measure 1.5 mL of liquid substance, and the 0.5 would be the uncertain digit. Thus, inwriting the measurement down as 1.5 mL, another scientist will read this as 1. mL was certainlythe measurement, and the 0.5 was an estimate that cannot be precisely determined from thedevice used to measure because it does not have that measurement marked. In this experiment, the purpose was to investigate the measuring capabilities of variousglassware and explore not only the precision and accuracy abilities of the various glassware butalso explore the use of significant figures. In order to do so, the concept of density had to beemployed to compare measurements of water between glassware. Density is calculated by using

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