Lab Notebook Policy

Chem 161 -162 -163

Instructor: Ken Marr

Revised Fall 2007

General Considerations

      Maintenance of an acceptable laboratory notebook will be emphasized in this course. Record keeping and data interpretation are skills that you will use throughout your scientific career. The ability to prepare an adequate and reliable record of results is a fundamental requirement for all successful experimental work.

      The most important criterion for an acceptable lab notebook is that the record be complete and neat enough for another person to easily follow your experimental work, thus being able to repeat the experiment and to obtain the same results. The recording of lab results, data and observations must be written directly into your lab notebook while you do your work in lab. Your records should reflect your work so well that any odd or erroneous results can be interpreted later, even if you don't notice the errors at the time. Later, outside of class, you can do the required calculations, interpret the data, etc.

      All entries in the laboratory notebook are to be made in ink. If errors are made, simply cross them out with a single line. Never obliterate entries and never use whiteout—at a later time you may find that this information is useful! All data and observations are to be entered directly into the notebook, not on scraps of paper. While you may want to wait to record data until after the lab is over in order to have a neat notebook, it is more important to have a complete, accurate record of all original data and observations, complete with smudges, spills, and cross-outs. Your laboratory notebook should provide a complete record of the work that you have done throughout the year in the lab. If it is necessary to omit information on a page in your lab notebook, place a large X over the information but do not remove the page from the notebook. Pages should never be removed from a lab notebook.

General Guidelines 

o       Lab notebook: Chemistry Laboratory Notebook: 100 Carbonless Sets of Pages with spiral binding (purchase at the GRCC bookstore!!)

o       Table of Contents: Before coming to lab enter in the table of contents the title of the experiment to be performed and the starting page of your report.

o       Prelab Assignment: A pre-lab must be written in your laboratory notebook before you will be allowed to participate in lab. Carbon copies of the pre-lab are to be “stamped” by the instructor before leaving lab. The pre-lab includes the following components written directly into your lab notebook in ink before coming to lab:

   Title and Date of Experiment, Your Name, Lab Partner(s), Course and Section

I.   Introduction

II. Materials and Method

III. Results (Data Table(s) should be prepared and ready to be completed before coming to lab!)

Lab Report Format

Unless told otherwise, use the following format when writing up all lab experiments. Each lab report consists of five clearly labeled and easily identified sections written directly into your lab notebook.  See the next page of a description of what should be included in each of these sections.

I.              Introduction

II.           Materials/Methods

III.         Results

IV.        Analysis of Results

V.           Conclusion

Title and Date of Experiment, Your Name, Lab Partner(s), Course and Section

I. Introduction

·      Describe/summarize in your own words (don’t plagiarize from the lab handout) the overall goal(s) of the experiment. What is it that you are trying to accomplish/determine with the experiment?  This is often called the purpose of the experiment. 

·      State any hypotheses (if any) that will be tested

·      Briefly summarize in your own words any relevant background information about the experiment and/or describe the theoretical principles on which the procedure is based, including all relevant chemical equations and/or algebraic equations.

·      Usually the introductory section takes up about half of a page to one full page.

II. Materials and Methods

·         The “Materials and Methods” section tells how the work will be done. It’s a step-by-step version written in your own words of what will be done—excessive detail is not required. Your procedure should be detailed enough that a competent student could use it to replicate the experiment. Complete sentences are not necessary and diagrams/flowchart/outline can and should be used where appropriate.

III. Results

·         Record neatly and directly into a ruled data table all measurements that are made during the lab period—pay particular attention to correct use of units and significant figures. Your data table should be easy to follow and should summarize the results of all major calculations, average result, the theoretical result, percent error, etc. See tables 1 and 2 for examples.

Table 1. Density determination of an Unknown Liquid #237

Table 2. Titration Data for the reaction of 0.100 M NaOH with an unknown acid

IV. Analysis of Results    Include in this section all calculations, analysis and discussion of your results.

1.      Calculations—clearly label what you are calculating!!

-        Show all calculations clearly, and with attention to significant figures and units for those experiments that involve calculations.

-        Before doing a calculation label clearly what you are calculating—do not leave it to the reader to figure out what is being calculated!!  Examples of each calculation should be provided corresponding to the table that depicts that result.  You need only show one sample calculation if that calculation is used repeatedly in the analysis of the data.

-        If there are questions assigned with the lab activity, answer them clearly, but concisely with full sentences.  Number your answers as the questions are numbered and make it clear to anyone what the question is that you are answering.

2.      Analyze your results fully by following these general guidelines:

-        State what conclusions can be drawn from the results and explain how you arrived at these conclusions.

-        Use specific numerical data and/or observations gathered in the experiment to support all conclusions you make

-        Explain why your results might be inconsistent with the predictions you made (what you thought would happen before you did your study, based on a specific hypothesis or other background information)

      Error Analysis. If possible, calculate the percent error:

-        Quoting the %Error, comment on the accuracy of your results and discuss the specific sources of error that may have caused your results to be too high or too low.

-        Discuss problems that arose in your study and how could they be avoided in the future,

-        If possible, compare your results with those of groups in the class and with the accepted/theoretical results. Cite the references used for comparisons (i.e. names of group members, website, reference book, etc.)

o        Compute the % error for the class data and comment on the accuracy of the class results.

o        Use Excel or a calculator to compute the standard deviation for the class results and then comment on the precision of the class results.

-        Explain what you may have done or could have done, if anything, to improve the experiment to get better results

V. Conclusion—Use “bullets” to state briefly, concisely and clearly summarize the major conclusions

• Use specific data to support your conclusions—that is, quote specific numerical results. It is not enough to simply state in the conclusion that you calculated a salt’s density or a salt’s heat of solution. Always use specific numerical data to support/substantiate your conclusions!! Here’s a sample conclusion:

o  Density of unknown salt #342:  2.030 g/mL (9.82% error and standard deviation of 0.402 g/mL) A likely cause for the higher than expected density and the poor precision was inaccurate mass determinations due to the fact that the salt is highly hygroscopic

o  The class average for the DH_soln salt #342:  -34 kJ/g salt (–7.7 % error and Standard Deviation of 2.5 kJ/g salt). The most likely cause for the lower than expected DH_soln was heat loss to the surroundings due to the poor insulating properties of the coffee cup calorimeter.

o  Our groups average for the DH_soln of salt #342:  -32 kJ/g salt (–13 %). Like the class average, the most likely cause for the lower than expected DH_soln was heat loss to the surroundings due to the poor insulating properties of the coffee cup calorimeter. Moreover, we used too large of a salt sample and had difficulty getting it all to dissolve, thus contributing to lower than expected results.