Name(s): _______________
Chem 120 / Dr. Rusay
DENSITY & Measurement
Complete the following:
Unknown Number Reference #
___________
Measure and record the cylinder's length.
___________
Measure and record the cylinder's diameter.
___________
Weigh and record the mass of the cylinder.
___________
DENSITY of cylinder (g/cm3)
___________
Identity of metal
___________
Volume of water in graduated cylinder + metal cylinder. ___________
Volume of water in graduated cylinder
___________
Volume of metal cylinder.
___________
Which method is most accurate in determining the density of the metal cylinder?
Briefly explain your choice.
Consider the Purdue University students’ data for the density of a U.S. penny.
Rank the four methods in order of increasing Precision & Accuracy:
Precision: ___ < ___ < ___ < ___
Briefly explain your choices.
Accuracy: ___ < ___ < ___ < ___
Experimentally Determining Density
Significant Figures, Accuracy, Precision and Data Analysis
Complete the form on the opposite side of this page: one per group with each group
member’s name is to be turned-in when finished.
1. Calculate the density of a metal cylinder using your linear measurements and the mass.
Be sure to have the correct number of significant figures. Identify the metal from its
density and show your results to Dr. R.
2. Using the same cylinder or a cylinder made of the same metal, record it’s mass and
measure its volume by displacement using a graduated cylinder and water. Enter your
data on the form. Calculate the density. Record the value and provide a brief discussion
of which method is more accurate.
A group of students at Purdue University applied these methods to “new” and “old“
pennies. (NOTE: Both the “new” and “old“ pennies that they used in the experiment were
in public circulation and not in mint condition.)
A group of students followed the following four different procedures for one set of “new”
pennies and another group repeated the measurements with “old” pennies.
Method 1:
The mass, height and diameter of a stack of ten pennies were measured respectively
using an analytical balance and calipers. The student data is provided in Table 1.
Method 2:
The mass, and volume of a stack of ten pennies were measured respectively using an
analytical balance and 100 mL graduated cylinder. The student data is in Table 2.
Method 3:
The mass, height and diameter of a single penny were measured respectively using an
analytical balance and calipers. The student data is provided in Table 3.
Method 4:
The masss, and volume of a single penny were measured respectively using an analytical
balance and 10 mL graduated cylinder. The student data is in Table 4.
However, unlike diligent and meticulous DVC Chem 120 students, the Purdue students
failed to record whether the data they obtained was for “new” or “old“ pennies.
3. Your indivdual challenge is to determine in your breakout subgroup which of the data
sets that you’ve been assigned to analyze is for the “new” and which is “old“ and the
precision and accuracy of the method. You must use significant figures and knowledge
of mass and volume measurements correctly.
4. Returning to your parent group, select one of the four methods as being the best
experimental approach in obtaining the most precise and accurate results, and then
ranking the four methods respectively in increasing order of 1) precision and 2)
accuracy.