ANALYTICAL WEIGHING, LIQUID TRANSFER, AND PENNY DENSITY REPORT
Name:
Date:
Section:
Analytical Weighing
Trial 1
Trial 2
Data
Units
Mass of Salt
Mass of Water
Experimental Mass of Known Object:
Known Mass:
Difference:
Methods of Determining Masses
(a) mass of wash bottle
(b) mass of dry beaker
(c) mass of weighing bottle with salt
(d) mass of weighing bottle with residual salt
(e) mass of beaker with salt
(f) mass of beaker plus salt and water
(g) mass of wash bottle after water transfer
Method 1(addition)
Method 2 (difference)
Difference in Methods (grams)
Difference in Methods (tenths of milligrams)
Difference in Methods (percentage)
Comments:
Trial 3
Pipette Transfer
Trial 1
Trial 2
Trial 3
Mass of beaker before water addition
Mass of beaker after water addition
Mass of water added
Lab temperature:
Water density:
Trial 1
Trial 2
Trial 3
Volume of water added
Average Volume delivered:
Rel. Std. Dev.:
Comments:
Post Lab Discussion Questions for Methods Section.
1.
Which method of weighing (addition or difference) do you think is the more accurate
method? Why?
2.
Why does the wash bottle lose very little water to evaporation?
3.
What impact on weighing do your fingerprints have?
4.
Why does the temperature of the lab play a role in the determination of water density?
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Penny Data
Your Graduated Cylinder Calibration Data
Trial
Final Buret Reading (mL)
1
2
3
Initial Buret Reading (mL)
Calibrated Volume (mL)
Average Calibrated Vol. (mL)
Standard Deviation (mL)
Your Sample Density Data
Trial
Number of pennies in sample
Sample Type (old or new):
1
2
3
Total Mass of Penny Sample
Final Buret Reading (mL)
Initial Buret Reading (mL)
Volume (mL) of water added to
the cylinder with pennies
Volume occupied by pennies
Penny Density (g/mL = g/cm3)
Density Uncertainty
Average Density (g/mL = g/cm3)
Standard Deviation Density (g/mL = g/cm3)
Show the calculation of the density uncertainty in this space:
Be sure to append and discuss a computer generated plot of mass of pennies as a function
of year as a figure in your report.
Complete the statistical testing described on the next page using your pooled lab data (list
those pooled results in the space at the top of the next page.) Finally, answer the associated
questions on the next page.
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Pooled Data for Graphing and t-testing will be provided via email (or hardcopy)
Prepare an x-y scatter plot of the mass (y-axis) vs. mint year (x-axid) of the pooled data for
your lab. Adjust the presentation of the data to make the presentation look professional.
Attach the graph to your report AND securely fasten a copy into your lab notebook.
If you need help learning to use Excel (the free spreadsheet tool available in WU public labs),
you should visit the CHM113 website and look at the link “Other”.
[http://www.chem.wilkes.edu/~mencer/chm113extra.html].
There is an Excel practice assignment there. It is self-explanatory.
Post Lab Calculations.
1. Use Excel to determine the average (mean) and standard deviation of the masses of the
two groups of pennies (older vs. newer)* and report the values here to the correct number
of significant figures.
*Note: In the 1982 mint year some pennies are of the “older” type while others are
of the newer type.
2. a. Use Excel to determine the average (mean) and standard deviation of the density
values of the two groups of pennies (older vs. newer)* and report the values here to the
correct number of significant figures.
b. Perform a t-test to determine if the difference in density of the old and new penny
groupings is “significant”. Show your work here:
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c. Perform a t-test comparing the old penny data pool to the accepted density of copper
(Cu). Does the test support the assertion that the old penny density is statistically “the
same as” or “different from” the known density of copper (Cu). Show your work here
and DISCUSS (especially in the context of estimated uncertainties).
d. Perform a t-test comparing the old penny data pool to the accepted density of zinc
(Zn). Does the test support the assertion that the old penny density is statistically “the
same as” or “different from” the known density of zinc (Zn). Show your work here
and DISCUSS (especially in the context of estimated uncertainties).
Post Lab Discussion Questions (entire lab).
1.
Would you characterize this lab as conforming to the Principles of Green Chemistry?
Support your answer.
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