A reminder of the objective and grading criteria
given in the original handout.
Objective
In this lab you will measure the density of
several substances. In addition you will use the known
density of aluminum (2.70 g/cm3) to measure
the thickness of aluminum foil. Successful completion of
this investigation will include:
The density of the following, as measured in
multiple trials:
A glass marble
A cork
Sand
Mossy zinc
A calculation of the thickness of household aluminum
foil
Neat data tables showing averages and precision
Grading
An individual formal lab report is due. If you
want to challenge yourself you may also do one of the
Above & Beyond Activities listed below. If you choose
to do one it will be graded on its merits and is not
‘extra credit’. The advantages of doing one
are two-fold: first, you extend your knowledge of this
chemical topic; second, you earn another grade, improving
your quarter average.
Comments on Lab Reports
for Density
The following comments may or may not apply to your paper.
I have noted on your paper numbers corresponding to the
numbers next to each comment below. If you intend to do a
second draft (a do-over) then pay particular attention to
these comments. If you do not need to do a second draft, or
do not want to, then pay attention to these comments
anyway: they will help you to do well on your next
assignment.
Results that are clearly wrong may be excluded from averages and graphs.
It is the nature of science to be self-correcting. This happens when people measure the same things other people measured in order to confirm or disprove their results.
Your writing is good: clear and
precise.
Your report is too long: eliminate unnecessary details, eliminate redundancy, use more concise language, make sure everything you write means something.
You clearly understand the
underlying science.
It is not clear whether you
understand the science. See me.
This was not written according to the given lab report format.
Incomplete—see me for
details.
The report has a professional
appearance.
The report is acceptable in appearance but has some flaws.
The report is messy, hard to read,
or shows signs that little or no care was used in writing
it.
Your graphs/figures are not well integrated into the report. Number them and refer to them by number in the text. Discuss what they mean: density is a intensive; there is direct proportion between m and V.
Your graphs do not display the slope, have reversed axes, or other problems.
Missing sample calculations or the calculations are incorrect.
You have failed to include calculations of experimental precision or they are incorrect.
More trials do not increase precision, especially if your measurements result in data with a wide range due to variable samples or technique. What having multiple trials does is allow you to calculate your precision by finding the range and ± amount.
“Human error” is a useless phrase. In science we measure the amount of error and explain its origins on the basis of the limitations of equipment. “Human error” is code for “mistake”: if you are aware of a mistake, fix it!
This document refers to the lab that can be found here.
Last updated: Oct 31, 2007
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