Chemistry 31 Laboratory Grading: Report and Quiz Schedule – Fall, 2016

 

Laboratory Experiment Report         Due Date     Grading          Tolerance#

1. Calibration of Buret/Pipet                  Sept. 19        2 pts                N/A  (0.1)

2. Chloride Lab                                      Oct. 17         11 pts              0.3  (0.5)

3. Water Hardness Lab                          Oct. 31         10 pts              0.5  (1)

4. Atomic Absorption Spectroscopy      Nov. 21        12 pts              6/4 (Mg/Ca)$

5. Ion Chromatography                          Nov. 28        10 pts              5

6. Spectrophotometric Analysis             Nov. 30        10 pts              2.5 ea. compound

7. Formal Water Report                         Dec. 5           10 pts              N/A

8. Soda Ash Lab                                    Dec. 9*         10 pts              0.5  (0.5)

9. GC                                                     Dec. 9*         10 pts              2.5

*It is recommended that you turn in these lab reports earlier in case you make any calculation errors.

#See notes 4 and 5 below for the meaning of the tolerance scale.

$ 6% tolerance is given for Mg vs. a 4% tolerance for Ca due to lower Mg concentrations.

 

Notes:

1.  Laboratory experiments must be turned in by the due date to receive full credit.  If laboratory reports are not completed or are in an incorrect format (see Appendix II of lab manual for correct format), they will be returned without grading.  Report due dates are roughly based on one week past the last day expected for in-lab work and may be postponed.  The penalty for late lab experiments is 2 points off for each week late.  Lab reports turned in after Dec. 9 (including recalculations/resubmissions) receive zero credit.  Also, some reports require calculations using a computer, so it is suggested that you try to do the calculations at least a few days before the deadline.

2.  Lab report formats:  Refer to Appendix II of the lab manual for the correct format of each lab report. Data sheets or photocopies of carefully organized lab notebooks are needed for most reports.  Reports 2, 4 and 6 require turning in a computer-generated spreadsheet (see example spreadsheets in the lab manual).  The formal lab report (number 7) will be a 3 to 5 page written report of the analysis of the tap water sample in the atomic absorption spectroscopy and the ion chromatography labs.  This report will be graded based on the writing quality and content.

3.  Grading will be based on precision (2 points each for labs 1, 2, 3, 4 and 8) and accuracy (remainder of points for labs 2, 3, 4 and 8 and all of the points in 5, 6, and 9).

4. Grading for accuracy will be based on the percent error calculated from the reported value and the true value.  A full score will be received if the percent error is less than a tolerance value (1st value shown above).  Percent errors larger than the tolerance will result in loss of points.  For example, an experiment has a 0.5 % tolerance and a student's percent error is 1.2%, that student would receive an 8.6 or a loss of 1.4 points for being 0.7% past (1.4 times) the tolerance limit.  There will be a minimum accuracy score of 40% of the points for completed reports.

5.  Grading for precision will be based on reported uncertainty.  If your percent uncertainty is less than the value listed in parentheses under tolerance, you will receive full credit.  For lab 4, you receive full precision points by correctly calculating the uncertainty associated with each measured concentration; the actual uncertainty value will not affect your grade.

(cont. on back)

6.  If it appears likely a poor score was the result of an incorrect calculation or if the initially submitted lab report was incomplete (and returned without grading), the report may be corrected and resubmitted.  The new report must be attached to the originally submitted report, must be resubmitted within two weeks of the original deadline (first 4 labs) or by Dec. 9th (last labs), and can only be resubmitted once for each experiment.  You may not resubmit the formal lab report.

7.  If you receive a low score, you may repeat one experiment if time permits.  However, students are limited to only one "free" replacement unknown request (subsequent unknown requests will be taken with a 2 point penalty).  No unknown request can be made after Dec 1st.

8.  Laboratory notebooks will be collected at random during the semester and graded for a total of 10 points.  It will be graded on 1) correct formatting (table of contents, page numbers, etc.), 2) inclusion of pre-lab calculations needed for current laboratory exercise, 3) a reasonable attempt to keep data organized, and 4) data entered correctly.

9.  The laboratory procedures quiz (5 pts) will be given on the fourth meeting of the lab (Sept. 8th or 12th) and be focused on reading the first 16 pages of the lab manual, understanding how lab grading is done, and on following safety and procedural information given in the lab lectures during the first week.

10.  As added incentive for students to turn in lab reports in the correct format the first time, 2 bonus points will be available for any student that: 1) submits all lab reports on time, 2) does not resubmit any lab report, 3) receives a score of at least 50% of available accuracy and at least 50% of available precision points for every lab report (excluding the formal lab report).  This is the High Quality Report criterion mentioned in the syllabus.