[Chm111-lab] Procedures for Lab Reports 1 and 2

[Andrew J. Pounds]

Okay -- several of you have been asking about this.  So here goes...

1. You will bring your completed lab reports to lab (in other words, 
labs are due the next time you come to lab)
2. You will be turning in TWO lab reports when you come to lab next time
3.  Each lab report will need a GENERALIZED LABORATORY REPORT cover 
page.  You can download these from my website.
              http://theochem.mercer.edu/chm111

4. You will complete the report forms available for each lab.  These are 
located on the same web page where you found the lab procedures.  I have 
them linked to my webpage given above.

Now this is where it gets tricky.

For the MEASURING UNCERTAINTY Lab, the report form contains a place for 
determining the density of an unknown solid.  DO NOT USE THAT SHEET.  
You will use the appropriate report form from the density of an unknown 
solid lab.

In the first part of the report form it tells you to record the average 
and average deviation (this is where you will use both your data and the 
data you collected from others in the lab).   What you should know is 
that traditionally in chemistry deviations are limited to ONE 
SIGNIFICANT DIGIT and that one significant digit is then used to help 
determine to how many places you can accurately represent the measured 
quantity.

For example, lets say I had four measured mass values:  23.33, 23.28, 
23.35, and 23.27.  The average, using straight sig figs, is 23.31.  The 
average deviation is 0.0325 (which is rounded to 0.03).   In this case 
the  reported  value would be 23.31 ± 0.03.    If, for example, the 
average deviation were 0.22, the I wouldn't be justified using the extra 
information and I would  record the value as 23.3 ± 0.2.   

I want you to complete part I.A. of the lab using this method.

You should attach a graph as noted.   I do not care if you use  Excel to 
prepare your graphs.   If -- however -- you construct graph paper by 
hand then you must use graph paper that has at least 10 division per 
inch.  USING THE BACK OF ENGINEERING PAPER FOR GRAPH PAPER IS NOT 
ACCEPTABLE -- IT IS NOT ACCURATE ENOUGH.  I will count the graph as not 
turned in if you do this.   If you do not have access to quality graph 
paper, you may print off some from my web page.   It is also available 
on the web page where you downloaded the procedures.   All graphs must 
have the axes clearly labelled, the data points identifed, and the BEST 
FIT LINE drawn on the graph (don't just connect the dots or you will 
evoke my wrath).   Use as much of the area on the graph paper as 
practical.   Your plot should fill the graph paper.  It should not be 
isolated to a small piece of the graph paper.

In the cover page of you lab report (which will be the GENERALIZE LAB 
REPORT FORM)  please remember to ALWAYS include you section number.   In 
the big blank area I want you to record the mass of one drop of water 
using the "±" notation described above.

Okay -- for the density of an uknown solid lab, please fill in the 
appropriate report sheet for the lab (which is downloaded off the web) 
and use the GENERALIZED LAB REPORT FORM as a cover sheet.   On the GLRF 
I want you to write down the unknown number of you solid, the density 
you measured experimentally, and your best guess at the identity of the 
solid.

Some of you have asked me about the CRC and the density of water 
literature value.   The CRC is the "Chemical Rubber Company Handbook of 
Chemistry and Physics".  You will find a copy in the Library.  You 
should use this to find the density of water at the laboratory 
temperature on the day you did the lab.

If you have any questions, please let me know.


-- 
Andrew J. Pounds, Ph.D.  (pounds at theochem.mercer.edu)
Associate Professor of Chemistry and Computer Science
Mercer University,  Macon, GA 31207   (478) 301-5627