# 1 Determine the Difference in Accuracy between a Standard...

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1 Determine the Difference in Accuracy between a Standard Centigram Balance and a Standard Electronic Balance INSTRUCTOR: Sunday, February 01, 2015 PURPOSE/INTRODUCTION

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2 The purpose of this experiment is to demonstrate alternate methods of weights and averages using two different scale designs. The first scale used will be a standard Centigram balance that measures to the nearest centigram. The second scale in the experiment is a standard electronic balance that measures to the nearest milligram. The hypothesis is that the centigram balance will be less accurate and more susceptible to interpretation by the user then the electronic balance will be. MATERIALS Materials required to test the hypothesis in a lab include: Centigram balance, 2 Electronic balance Beaker, 100mL Watch glass Copper slug-cu, 5 Iron weight of unknown value, 4 Sodium chloride- NaCl, 1.2g
METHOD Part One: Determine the deviation between two centigram balances using a single copper slug to demonstrate the inaccuracy of this type of scale. Place a single slug on one centigram balance. Using the direct-weighing technique, record the findings in the table on centigram balance section; centigram balance direct weigh; mass of slug balance one row. Weigh the same slug on the second centigram balance and record the mass of the slug on centigram balance section; centigram balance direct weigh; mass of slug balance two row. Part Two: Demonstrate method of weighing by difference. Weigh the same slug by utilizing the difference method. Determine the mass of an empty 100-ml beaker by obtaining a 100-ml beaker and placing it on the pan of the empty centigram balance. Record the mass of the beaker in the designated area on the weight table. Now place the slug used in the previous measurements inside the beaker and record the mass of the beaker and slug. Calculate and record the mass of the slug by subtracting the mass of the beaker from the combined mass of the beaker and slug. Record the finding in the designated row of the weight table. Repeat these steps and record your findings to determine the variation of the second centigram balance. Part Three: Weigh an unknown mass on a centigram balance using the direct- weighing technique. Place the iron weight directly on the centigram balance plate; record the identification number of the weight being used and the mass of the weight. Weigh the same iron weight on the second centigram balance using the weight difference method. Determine the mass of the empty 100-ml beaker by placing it on the scale and recording the finding on the table. Place the iron weight inside the beaker and record the combined mass of the beaker and weight. Calculate and record the mass of the unknown and record on the table.

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