Maintenance of an acceptable laboratory notebook will be emphasized in the General Chemistry Laboratory courses. Record keeping and data interpretation are skills which 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 enough for a second person to be able to follow your experimental work, thus being able to repeat the experiment and to obtain the same results. The record must be written while you do your work. Your records should reflect your work so well that any odd results can be interpreted later, even if you don't notice them at the time. Later, you can do calculations, 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; 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.
For each experiment, organize your notebook into sections beginning with appropriate headings. Carbon copies of your lab book pages are to be submitted weekly as a lab report. (See below for more details on report writing.) Lab reports are submitted in two parts: the pre-lab, purpose, and procedure, which is turned in on the day the experiment is performed, which is submitted at the beginning of the period on the day scheduled for that lab. Data, calculation, results and discussion/conclusion sections and post-lab questions, are to be turned in at the beginning of the period on the day scheduled for the next lab. If not turned in by this time, they are considered to be late and subject to a late penalty (approximately 10% of the total available points per day late).
In general, the following three questions will be asked in evaluating each section of your laboratory reports for a grade:
The following information must be included at the top of every page:
Your name
Date
Experiment # and Title
Pre-lab, Data, and Observations:
Title: The title and number of the lab being performed.
Sources: Where the procedure came from and any other sources used. Cite any literature or web sites used.
Purpose: This is a brief description of why you are performing the experiment and what you expect to learn. Do not copy the purpose straight from the lab book!
Example:
Prupose: To determine the percent water in an unknown hydrate salt.
Procedure: A step-by-step version written in your own words. This should be detailed enough that someone else could use it to replicate the experiment. Complete sentences are not necessary and diagrams can and should be used where appropriate. Tables are often useful for procedural descriptions and can dramatically reduce the length of the procedure section. Make this section brief , complete and in your own words!
Example:
Procedure: Clean crucible
dry to const wt. w/heating
add about 5g unknown
heat gently 1st, then strongly for 10-15 min
cool-weigh-reheat-cool-weigh-repeat to const wt.
Data and Observations: Before you leave lab, all relevant measurements and observations must be recorded directly in your laboratory notebook. Include anything noteworthy that you observe such as color and temperature changes, formation of a precipitate, etc. Large collections of data should be organized into tables for clarity. All numerical entries must have appropriate units and correct number of significant figures. It is not necessary for this section to be extremely neat, but it should be legible and in some sort of order. If you make a mistake recording data cross it out with ONE line. If you have to cross out an entire trial use a large X, and include a brief note as to why you did not include the data. Don't forget to record the numbers of any unknowns.
Calculations, Results and Discussion/Conclusion:
Calculations: Calculations should be presented in such a way that the person grading the lab will be able to follow them. For experiments which involve more than one trial, it is only necessary to show one set of calculations and record the final result for each trial in a table. Be sure to include units where appropriate. The use of tables for data and calculations is always recommended. This provides a quick and easy way for the grader to find the appropriate information.
Results: The results section is a simple concise statement of what was determined by doing the experiment.
Example:
Results: Unknown # 001-325 contains 15.226% water.
Discussion/Conclusion: This is a recap of the lab and the place to show what you learned. A general outline of the components of a good discussion follows. (This should all fit on one page or less.)
Note: The above two items can be treated in as few as one or two sentences.
Example:
Discussion/Conclusion: This experiment was performed for the purpose of determining the concentration of acetic acid in an unknown sample. This was accomplished by titrating the sample with a known concentration of sodium hydroxide until the phenolphthalein endpoint was observed.
Note: The following items should be considered when writing your conclusion and included when appropriate. This may require several sentences.
 | what did you measure? |
| what do the results tell you about the problem? |
| are they "good", "bad", precise, accurate, too high, too low? |
| what are the possible errors? |
DO NOT merely list possible errors. DISCUSS the ones that may have shifted an otherwise reasonable answer in the direction of an erroneous one. Consider what effect will an error make on your result.
Example-Discussion/Conclusion (continued):
The theory involves the neutralization of acids and bases where the moles of acidic hydrogens are equal to the moles of the base used to neutralize it at the equivalence point. Since phenolphthalein was used as an indicator, the end point and the equivalence point are fairly close to each other. All volumes were to measured .01 ml, and the standardized NaOH solution was .1102 M leading to an accuracy for the concentration of acetic acid of .001 M. Our results were slightly higher than the class average, which stands to reason considering many of the end point of other students were flaming red making their results too low. We are therefore confident that our results are accurate since all end points were the slightest pink perceivable.
Post-Lab Questions: Frequently, additional questions will be assigned. Answer these on the sheet provided in your lab packet and turn in with your lab notebook.
The general flow of the the typical lab: The following is the general order of events for each lab.
Before Lab begins