Precision and Accuracy Essay

Submitted By himynaameis
Words: 1331
Pages: 6
Open Document
Trends in the Mass of a Penny

Abstract:
Before the year 1982, pennies were made up of a majority of Cu. However, after that year, the composition of pennies changed to a majority of Zn. Our graph of the masses of ten pennies and the year they were minted in showed a trend in the masses of pennies before the year 1982 and after 1982. In order to find out what caused this change, we used the density of the pennies. Density is an intensive property of a system which means it is “a physical property of the system that does not depend on the system size or the amount of material in the system.” So we took the laboratory further and found the masses and volumes of groups of pennies separated by whether they were minted before or after 1982. By graphing the mass vs. volume of these samples, and finding the densities of each sample, we found that it was a change in penny composition which supports the fact that after 1982, pennies were made with a zinc core and copper coat instead of mostly copper. Also, we proved the changed in composition by putting a nicked old penny and a nicked new penny both into a solution of HCl (hydrochloric acid) and the new penny was the only one to react.
Introduction:
Pennies minted before 1982 were made up of a mixture of 95% copper and around 5% zinc. However, after awhile, making pennies with such a high content of copper became too expensive. Instead, pennies after the year 1982 were minted with a zinc core and a copper coating, around 97.5% zinc and 2.5% copper. The differences in the pennies compositions changed many of their characteristics. Changing the composition of an object and keeping the volumes constant means some properties of the object such as the mass, density and some chemical properties of the object must have changed. So the penny densities were changed and their reaction to HCl changed as well. In this lab, we analyzed penny masses to determine trends between the masses, the years there were minted in, and the causes of these trends. We calculated the densities of the older and newer pennies by graphing our obtained values on a mass (g) vs. volume (mL) graph, giving us the density. The results we obtained explained why the masses before 1982 followed a certain trend in their masses and why after 1982 they followed a different trend. These results supported the historical fact that the composition of pennies was changed that year.
Experimental:
For the first part of the laboratory, we used a 50-mL graduated cylinder, a 50-mL buret and some tap water to find the averaged calibrated volume (V) of the graduated cylinder. First, we filled the buret with water and recorded the initial volume reading to the nearest hundredth of a mL. Then, we filled the graduated cylinder to the 45.0 mL mark without letting the buret volume fall lower than the 50 mL mark and took the final buret volume reading (again, to the nearest hundredth). We repeated the procedure two more times, calculated the calibrated volume for each of the three trials by subtracting the initial V from the final V, and then calculated the averaged calibrated volume of the 3 trials, recording it all in a table. Then, for the second part of the procedure, we used 10 pennies (a mixture of old and new), weighed each one and recorded each mass, along with the year they were minted, in a table. We first found the mass of each of the samples and recorded the masses to the nearest thousandth of a gram. Then we filled the buret with water, recorded the initial buret reading, added a bit of water (around 5 – 10 mL) to a dry graduated cylinder and slid the group of the 4 old pennies into the cylinder, tapping at the cylinder to make sure there were no air bubbles in between the pennies. Then we finished filling the graduated cylinder to the 45 mL mark and took the final buret reading, recording it to the nearest hundredth of a mL We redid this final and initial reading for both of the other groups of
Show More

Related Documents: Precision and Accuracy Essay

The Difference between Precision and Accuracy Essay

Abstract The purpose of this experiment is to understand the difference between precision and accuracy. One person measured the length of a laboratory table with a 20cm wooden rod while another person measured the width of the same laboratory table with a separate 20cm wooden rod. This was repeated 30 times. Data was collected to find the mean, standard deviation, percent discrepancy, relative error, and the normal distribution. Later in the experiment, the actual value of the length and width…

Words 833 - Pages 4

Explain The Difference Between Precision And Accuracy

Explain the difference between precision and accuracy. Suppose you made three different mass measurements of a sugar sample you knew to have a mass of 1.00g. How would you know whether or not the measurements were accurate? How would you know whether or not they were precise? Could the three measurements be precise, but not accurate? Explain. The difference between precision and accuracy is that precision is how close the measurements are to another, and accuracy is a measure of how close a measurement…

Words 752 - Pages 4

Essay on Chem Pre Lab

Marriah Miranda CHEM 1411 February 4, 2015 Precision and Accuracy of Scientific Glassware Pre-Lab Report The objective of this experiment is to learn which scientific glassware should be used in various circumstances, how to measure volume and mass and how to record laboratory data and observations. Become familiar with significant figures, errors, precision and accuracy associated with the various tools and techniques. To Contain Glassware you will need two Erlenemeyer Flasks, one 125 mL to measure…

Words 972 - Pages 4

Essay about Chemistry: Measurement and Gas Mileage

Chemistry and Society Paper Sharitte Smith CHM/ 110 July 20, 2015 Yihong Cao Kaufmann Chemistry and Society Paper The differences between accuracy and precision “In the field of science accuracy is the form of measurement that calculates the degree of closeness of a quality to its true value. Precision is a unit of measurement that is also referred as the ability to reproduce the same results multiple times” (Taylor, 1997). The differences are within the description, it all depends on what you…

Words 797 - Pages 4

Essay on Pipet Lab

Pipetman Lab Purpose: To determine the accuracy and precision of the pipetman. Accuracy The ability to obtain data equal to a known value. Precision is ability to obtain consistent data. Background: A pipetman is a laboratory tool used in chemistry , biology and medicine to transport a measured volume of liquid. Pipetman come in many designs for many purposes and much different levels of accuracy and precision . Pipetman come from in many varieties such as a single piece glass…

Words 747 - Pages 3

Physical Science Essay

inaccurate markers. Precision vs. Accuracy Precision is often referred to as reproducibility or repeatability. For example, consider the precision with which the golf balls are shot in the figures below. A set of shots that are only precise would mean you are able to cluster your shots near each other on the green but you are not reaching your goal, which would be to get the golf balls into the hole. This concept is illustrated in the left picture of the two figures below. Accuracy, on the other hand…

Words 328 - Pages 2

Experiment 1 Essay

coke in order to evaluate the precision and accuracy of the measurements. Precision refers to the degree of reproducibility; accuracy expresses how closely the measured value correlates to the “true” value of a quantity. However, many errors in measurements can change the precision and accuracy of measured values. Random error, which occurs from minor variations in the quantities measured due to the limitations of the measuring process itself, can affect the precision of a set of measurements. The…

Words 893 - Pages 4

week 1 paper

between accuracy and precision. Accuracy is the closeness between what we measure and what we believe to be true, while precision is the closeness to one another of repeated measurements gathered of a certain variable. Therefore, if a measurement is far from what we expect it to be, it is not accurate. If we obtain multiple measurements of a certain variable and the results are far from each other than these results are not precise. As we go through our daily lives, we depend on accuracy and precision…

Words 835 - Pages 4

Uncertainty Principle and Quantum Mechanics Essays

four properties; in particular, they have to do with the precision with which these properties can be measured. Up until the advent of quantum mechanics, everyone thought that the precision of any measurement was limited only by the accuracy of the instruments the experimenter used”. (American Institute of Physics) Also it is shown that “Heisenberg showed that no matter how accurate the instruments used, quantum mechanics limits the precision when two properties are measured at the same time. These…

Words 702 - Pages 3

02 Measuring Mass Length Volume And Den Essay

with the maximum precision. The rules for the use and importance of significant figures. How the choice of measurement device affects the quality of measurements. Review calculations of volumes of regularly shaped objects from their dimensions. Familiarity with the concept of density. Should know how it is used to identify samples qualitatively and should be able to use it the interconvert between mass and volume. How to properly use a volumetric pipette. Define accuracy and precision. Determine the…

Words 3606 - Pages 15