Precision and Accuracy
Erin Rafferty
Koby Jones
Logan Gililland
Marina Barto
TA: Ricardo Ortiz
Wednesday 10:30 am
Introduction:
Since there are several different pieces of equipment in the laboratory used for
measurement, it can be difficult to decide which is the most accurate and precise for certain labs.
In this specific lab, we were expected to familiarize ourselves with the laboratory glassware by
accurately measuring liquid volume, using a balance, and comparing our results. We were also
asked to compare our results with theoretical volumes which were measured from the mass and
theoretical density of water.
In order to solve this problem, we developed a procedure or plan which would be
referenced throughout the experiment to ensure that we were on the right track. Our plan was to
perform several measurements to find the mass of water and then use the theoretical densities in
order to calculate the volume of the glassware. The temperature of the water used for the
experiment was 22.5
℃
so the theoretical density was 0.997655 (
2
). This would help us to find
the percent error and determine which glassware would be the most accurate.
The educational purpose of this lab is to become more familiar with the lab material so
that we could use it for future experiments. This lab encouraged us to find masses, volumes, and
densities of different objects to further our knowledge of the density equation:
Density = Mass/Volume
We also found several different measurements and learned how to put all of our
information into tables and accurately calculate percent error at the end of each calculation.
Percent error informs us of the experimental measurement accuracy:
% Error =
X 100
Accepted
V alue
Experimental
V alue
−
Accepted
V alue


Additionally, we needed to find the different concentrations and volumes of stock
solutions and compare them as ratios in order to determine the volume of the stock solution
needed for this experiment. The following dilution equation was used for part 4 of this
experiment:
V
V
M
1
1
=
M
2
Procedure/Experimental:
First, all the materials were gathered: a 600mL beaker, a 50mL beaker, a graduated
pipette, a buret, and a 10mL graduated cylinder. The 600mL beaker was filled with
approximately 300mL of distilled water. The water temperature of the water was determined to
be 22.5
°C
using a thermometer. The 50mL beaker and 10mL graduated cylinder were cleaned,
dried, and weighed while empty. Their masses were recorded in Tables 1 and 2 respectively. The
50mL beaker was filled to about 30mL with water from the 600mL beaker and its experimentally
measured volume was recorded in Table 1. The full beaker was then weighed and its mass was
recorded in Table 1. This was repeated for 2 more trials in order to include variation. The actual
volume of the water was then calculated using the equation for density. The percent error for the
experimentally measured volume was calculated. Next, the 10mL graduated cylinder was filled
with approximately 7mL of water from the 600mL beaker and its experimentally measured
2