[CHM 112] Lab Graphs

[Andrew J. Pounds]

In general I will want you all to use Microsoft Excal, OpenOffice, etc., 
to generate your graphs that have linear relationships.   This week, 
however, forcing you to do that could be cumbersome.  I have a comguter 
generated graph created on  the class website using the data from this 
lab -- and it took me a long time to do it.   My recommendation is that 
for this lab you do it by hand on good graph paper (not the stuff in 
your lab notebook).  You can also do it on your computer, but only do 
one graph per sheet (unlike mine which had all six sets of data on one 
graph).

Here are the things I check for when I grade graphs:

 1. Are the axes in the right positions and appropriately labelled
 2. Can I clearly see the data points
 3. If there is a linear trend, is it indicated properly (never connect
    the dots)
 4. If a linear regression is done, is the equation on the graph and
    easy to read
 5. Does the graph fill the entire sheet

Number five is a sticking point with me -- if you are making a graph use 
as much of the sheet of paper as you can.  Don't create a graph that 
uses one quarter of the sheet of paper.  Also, make sure that your data 
fills most of the graph area.  Don't obsess over this -- but do try to 
do it correctly.   If you would like me to look at your graphs before 
you submit them for the first time I will gladly do that Monday morning 
before class.

Now for the freezing point depression lab you will have to essentially 
draw two best fit lines on each graph.  I am not asking you to do linear 
regressions at this time; just draw the best fit line through the 
portion where the solution cools quickly and then another line through 
the lines where it slows down (see my example).  Extrapolate these two 
lines to their point of intersection -- and that is the freezing point.

Let me know if you have any questions.


-- 
Andrew J. Pounds, Ph.D.  (pounds_aj at mercer.edu)
Professor of Chemistry and Computer Science
Mercer University,  Macon, GA 31207   (478) 301-5627
http://faculty.mercer.edu/pounds_aj

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