Determination of the pKa of an Unknown Weak Acid. Determination of the pKa of an Unknown Weak Acid. The lab report structure naturally follows from the basic logic of the “scientific method.” The problem is presented, the experimental approach is listed, the data are shown, the results are tabulated, and the conclusions drawn.
I. Title Page (does not need to be a whole page) & Abstract
If you want to design a report cover with a creative image relevant to the experiment, that’s fine. It’s also perfectly fine to keep it plain. Do not procrastinate by finding just the right “eye candy” if you are struggling to find enough time to do calculations right. At a minimum, you must include the title of the experiment (it is fine to use the one I put in this manual), your name (put partner names in parentheses), the weekday & date of the experiment.
The Abstract goes just after the Title. We normally set it off in its own box beneath the title. The art of creating the perfect Abstract can seem a mystery to some, but if you limit yourself to stating:
the objective of the lab,
a sentence or two on the experimental approach used to meet that object,
a statement of the results (usually numbers, percent errors, and the like)
What doesn’t go in the Abstract: experimental procedure steps, raw data, observations, error discussion. All of these important things have their places in the full report. The purpose of an abstract is to give enough information on what was investigated and found so that the reader can decide if they wish to invest time in the full report. Abstracts are a normal part of professional scientific literature (articles).
You MUST must must make the first sentence of this section your Purpose statement. I will be reading your first sentence very closely, and if it is not clearly about the purpose of the experiment, you will lose 5 points right there. It is necessary to focus tightly on what we are trying to discover, verify, learn etc. This will give your Introduction, one of the more important sections of the report, a very good start, as it directs you exactly what to write next.
But, in my experience, what do people tend to want to do instead?
Sometimes they focus on some tiny aspect of the procedure right off the bat, and get bogged down, running out of steam before getting to the actual Goal. Or they might attempt to write a whole dissertation (heavily adapted from Wikipedia) on the theory the lab deals with (save that energy for your tutorial). At any rate, they get stuck with some form of Writer’s Block; by simply stating the purpose of the experiment, you can get your first major line written quickly. What could be better than that?
Again, what I don’t want to see here is everything the Web says about this general topic. This would be a clear example of plagiarism anyway! And it is easier than ever to check where suspicious lines of text may have come from. Likewise, do not waste time copying word-for-word the whole introduction I wrote in your manual. That is just plagiarism again. No matter how many pages of stuff you write (or worse, cut and paste), it will get heavy deductions if your introduction misses the key issues of OUR EXPERIMENT.
Without getting bogged down ahead of time about the Procedure followed, you will show why this experiment should help us address the purpose laid out in your very first sentence. This section, which can get long, also should set the background of your experiment. What Law(s) are being used/tested? Use your best judgment if there is a strange new term (like hydrates) that should be explained. If there is a chem reaction, definitely show it, since that is chemistry and this is chem lab.
You also must cite sources where you found specifics when putting together your introduction (there are specific standard formats for citing websites…find out what they are and use them). The chem textbook can be a resource too. Citations should be included in the text, not just in a bibliography at the end. You may follow any standard format for citations2 such as this type of superscript numeral or author name and year of publication like this: (Hallows, 2012), as long as you do it in a consistent standard style. Definitely get help on citation methods if you feel shaky about this!
This is analogous to the Methods part of what some refer to as “Materials and Methods.” Do not copy down a list of all equipment and chemicals used. That is required in some formats, but not here.
This may surprise you, but you should try not to describe every tiny step of the procedure in detail, nor of course should you ever cut’n’paste my Procedure word-for-word. Instead, you should give an outline of what was done – in your OWN words. This can be done as a numbered or bulleted list, or even as a paragraph (though people may not feel comfortable with that til later in the year).
So, how will your Procedure be different from the one I wrote for you to follow in the manual? When you write, your task is different from what mine was when I was talking you through the process of doing the lab (you are learning, there are points of caution to note, there are things to see, etc.). When you write your procedure, you are not to spit back the cautions, the notes, and so on. You are just quickly summarizing what you actually did (NO data, NO results go in the Procedure section). By the time you write your report, the experiment is in your past. I write the procedure as instructions to students, so there will be some extra info to help, but that is not essential procedure as far as what you include in your report. Therefore, you should write in the past tense and detail what you did. For example, in the Beach lab if you were told in the Procedure to use a clay triangle with the Bunsen burner, but you used wire gauze instead, just discuss the wire gauze. You don’t need to say we were supposed to use a clay triangle but we used the wire gauze because we were out of clay triangles, or whatever. You will gradually learn what is important to note, and what is a time-waster.
Here is another thing that confuses students sometimes. Think of how it reads, to me, when I get a lab report that says for example, “Weigh out 50.00 grams of salt.” No! Think of the point of view you are taking as the writer of a chemistry lab report (not a lab manual; it was my job to write the manual). You need to express this idea by saying, “Approximately fifty grams of salt were weighed out.” Keep it in the past tense. But wait, shouldn’t you be totally precise on the mass used?????? No, not in Procedure, because that level of precision comes later, in the Data section. Consider what would happen to your “brief” Procedure section if you ran three (or more!) trials…would you put three precise masses in the Procedure? No.
Present your data in the most clear, concise and meaningful way possible. This is usually in the form of a well organized, labeled Table. Do not attempt to design one giant table to contain all the various results from a long and varied lab. A few short tables might make a lot more sense. Remember that important data may not take the form of numbers at all, but can be recorded as brief sentences that report the observation, for example, “Steam immediately was seen after the reactants were mixed.” Observations such as this go in your Data section too, but may not fit well in a table.
PAY ATTENTION TO THE BIG DIFFERENCE BETWEEN DATA AND RESULTS! They are not the same thing, nor are they interchangeable terms, and so they do not get lumped together into one huge mathy section!! Please do not write a single heading in your report that says “Data and Results.” Data is something you record from measurements/observations in the lab, and Calculations are something you produce by processing the data, often with the aid of a computer or calculator. You can find results at home. You can not get data at home. This is your rule of thumb:
Data ≠ Calculations
Data ≠ Results (calculations and graphs are each a subset of Results)
V. Results. Raw data is not in the Results section, but has been presented before this. Handwritten calculations can be neatly copied onto fresh paper for incorporation into the report. Generally the first attempt at solving a lot of math is not neat enough to put right into a report. Calculations are the only portion of the report that can be handwritten. They must be completely labeled as to what you are solving for in each calculation, and must use appropriate sig figs. Visually highlight the big results of calculations so that they stand out.
Results can also take the form of a table or graph. Be sure to keep any raw data in the Data section. Graphs need titles, and each axis needs a label as well. The larger the graph, the easier it is to read. Make no graphs smaller than one half-sheet of paper. Instructions for graphing with Excel for Mac 2016 are included later on.
The Discussion is generally where you give your interpretation of what the Results mean. Never assume that the Results tables will “speak for themselves,” or that your Reader is willing to read your mind on what the meaning of it all is. You have to explain it. A big part of your grade will come from this section, because it is where the logic and reasoning (learning) come into play.
So, how to write this important section? Recalling the importance of the first sentence you wrote in your Introduction, your first sentence in the Discussion MUST reflect DIRECTLY back to the purpose, as in something like: “The results of this experiment proved the validity of the Combined Gas Law.” Again, you can avoid Writers’ Block by getting into the habit of doing this first thing automatically.
Then of course you need to proceed to show how your results logically have lead you to this statement! You can’t get away with simply telling me, “This experiment was a success.” Or even, “This experiment was a failure.”
Do not let yourself run out of time and energy on the report before writing a good Discussion, even if you believe the results are no good. This section is worth a lot of points.
Your discussion should (believe it or not) include some educated guess work about what may have gone wrong. Since we spent time studying statistics, when you have found a standard deviation or percent error, you definitely need to consider that in your Discussion. If your results stink, you need to face it head on rather than not owning up to what you think went wrong (or know went wrong). At this course level, you are not docked as heavily as you may think for bad results, AS LONG AS YOU GIVE CAREFUL CONSIDERATION TO WHAT HAPPENED…that’s where the real education happens. On the other hand, blowing off obviously bad results with no effort to Discuss will get you a heavy deduction.
In my class (though other faculty may feel differently) the Discussion is the one place in the report where it is appropriate to let your own “voice” come through, including the use of “I” and “we.” Do not, however, give free reign to sentiments such as “This experiment was too long and we should not have had to do so many trials.” [I kid you not…] That does not add to a useful Discussion.
VII. Summary Table
I generally tell you during the pre-lab what items must be included in the Summary Table. The Summary Table comes near the very end of the report (before Cited References). It will contain the BIG results. For many experiments this consist of only two entries, an unknown vial number and a percentage. Think, “Bottom Line.” The items in the Summary Table will come directly from the stated Purpose of the Experiment. I read the Summary Table first to get a handle on how this whole lab experience went for you. Then I go to the beginning and read it straight through.
This section gives any publications that are referred to in the report. The references should be complete, full references that anyone could use to find the publication. All sources of information should be included: lab handouts, websites, textbooks, other books, personal communications, etc. Citations should be included in the text. Citation style is up to the student but should be one of the recognized formats (APA, ACS, etc.) and be used consistently throughout the report.
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Determination of the pKa of an Unknown Weak Acid
Determination of the pKa of an Unknown Weak Acid