Balance Lab
Balance Lab of a Copper Slug and Sodium Chloride (NaCl) on a Centigram and Electronic Scale
PURPOSE/INTRODUCTION
The purpose of this experiment is to learn how to weigh a substance on a centigram scale and an electronic scale through direct weight or by weight difference. The hypothesis is that all scales used should show the same weight for a given sample. The experiment should show precision and accuracy of the equipment being used. This will allow a better understanding on how to properly weigh a given sample and what scale is more accurate.
The following are definitions of terms used:
Precision refers to the closeness of the set of values obtained from identical measurements of a given quantity. Accuracy refers to the closeness of a single measurement to its true value.
To determine the difference between two measurements the following formula was used: Δ Weight = Weight A – Weight B (1)
To determine the average of all the weights the following formula was used: a = ∑X1 + X2 + X3 +…XnXn (2)
MATERIALS
Materials required to test the hypothesis in a lab include: * * Centigram Balance (Qty. 2) * Electronic Balance (Qty. 1) * Beaker, 100 mL (Qty. 1) * Watch Glass (Qty. 1) * Copper Slug (Qty. 5) * Unknown Mass (Qty. 1) * Sodium Chloride (1.0 to 1.2g)
METHOD
Part One: To find the direct weight of an object using a centigram balance.
Use centigram balance #1. Clean the platform with a lint free cloth and check that all weights on the beams are in the zero position. Check to make sure that the centigram beam indicator aligns with the arrow on the stand. If zero, place object in the center of the platform and move beam weights until the beam indicator realigns with the arrow. Record the weight measurement.
Figure 1 – Centigram balance with copper slug
Repeat directions for part one on centigram balance #2 using the same object and record the weight measurement.
Part Two: To find the weight of an object
PURPOSE/INTRODUCTION
The purpose of this experiment is to learn how to weigh a substance on a centigram scale and an electronic scale through direct weight or by weight difference. The hypothesis is that all scales used should show the same weight for a given sample. The experiment should show precision and accuracy of the equipment being used. This will allow a better understanding on how to properly weigh a given sample and what scale is more accurate.
The following are definitions of terms used:
Precision refers to the closeness of the set of values obtained from identical measurements of a given quantity. Accuracy refers to the closeness of a single measurement to its true value.
To determine the difference between two measurements the following formula was used: Δ Weight = Weight A – Weight B (1)
To determine the average of all the weights the following formula was used: a = ∑X1 + X2 + X3 +…XnXn (2)
MATERIALS
Materials required to test the hypothesis in a lab include: * * Centigram Balance (Qty. 2) * Electronic Balance (Qty. 1) * Beaker, 100 mL (Qty. 1) * Watch Glass (Qty. 1) * Copper Slug (Qty. 5) * Unknown Mass (Qty. 1) * Sodium Chloride (1.0 to 1.2g)
METHOD
Part One: To find the direct weight of an object using a centigram balance.
Use centigram balance #1. Clean the platform with a lint free cloth and check that all weights on the beams are in the zero position. Check to make sure that the centigram beam indicator aligns with the arrow on the stand. If zero, place object in the center of the platform and move beam weights until the beam indicator realigns with the arrow. Record the weight measurement.
Figure 1 – Centigram balance with copper slug
Repeat directions for part one on centigram balance #2 using the same object and record the weight measurement.
Part Two: To find the weight of an object
References: Ebbing and Gammon. (2011). General Chemistry, Ninth Edition. California: Brooks/Cole. Model Science Software Product, Model ChemLab, vs 2.5, Balance Lab