3rd person past tense lab report

So You Want To Write A Group Lab Report
General Guidelines:

1.) Group lab reports are due _____________________________ to _________________________ by _________________AM/PM.

2.) Lab reports must be typed, double-spaced on letter-sized paper and 12 point font. Graphs and tables should be computer-generated using a spreadsheet program like MS Excel. The computers in the LRC (H-137) already have MS Excel and Word installed, but you will need M&G to print.

3.) After you write a few lab reports you should begin to develop an intuitive feel for what is and is not appropriate for a given experiment. This will only happen, however, if you continuously participate in the writing process. It may seem like a fair division of labor to have one group member write the whole report on a rotating basis, but in fact this just means that you are writing lab reports without the benefit of past experience; the fourth lab report handed in would still only be the first by that group member. In the end how you divide up the work is left up to individual groups, but past experience has shown that when the lab report was a group effort their grades improved.

4.) Your laboratory manual suggests that proper lab reports are written in the passive, third-person voice. This is true for professional-level journals, and will be preferred here as well as in many of your other chemistry classes.

5.) Remember that your lab reports are not only being graded on how well you performed the experiment but also on how well you report the work you did. Thus as long as your report is well written and demonstrates a clear understanding of the principles being investigated your data need not be perfect.

The Lab Report: (Your lab TA may specify slight modifications to the format below).

1.) Title Page: The title page is usually centered top and bottom as well as left and right and should contain the title of the lab (don’t just write “Investigation #”), the names of each of the group members, the date the lab was concluded, TA name, and section of the lab. Ex: CHM 113EA

2.) Introduction: The introduction of a scientific report is meant to give an overview of the entire experiment without delving into the precise details of your experimental method or results. Your introduction should be concise (at most two brief paragraphs) where you state:

· The experimental goals

· A short background (This includes the chemical theory, concept, method, and mathematical or chemical equations that are central to the investigation.). Do not show detailed calculations used for calculating results but can include general equations, e.g. the Ideal Gas Law, PV = nRT, in describing theory.

· Your general approach to solving the question or problem

· Do Not:

· Copy goals from the lab manual word for word

· Give detailed methods used in the lab

· Describe or report final results

Example:

The goal was to determine the identities of several unknown samples of metal provided. Metals possess a wide range of chemical and physical properties; by measuring a few such properties and comparing them to tables of known values the identity of each of the unknown samples were obtained. Most metals have a characteristic density, ductility and conductivity. In some cases luster and color are also distinct enough to aid identification. By measuring multiple properties, a sample was identified if two or more properties overlapped. Given the resources available it was decided to observe and measure the color, density and conductivity of the unknown samples.

Example:

The lab manual told us to measure the color, density and conductivity of the five metal samples we were given and determine which metals they were. We weighed the samples on the balance then calculated their volumes using a ruler and geometry. One sample was reddish orange, two were dark gray, and the other two were a dull silver. We used the Handbook of Chemistry and Physics to look up the densities, conductivities and colors of common metals and compared them with our data. Based on densities our samples could have been lead, copper, tin, iron, aluminum or titanium. Comparing this list against the list of conductivities we determined our sample was not tin which meant our samples were lead, copper, iron, aluminum and titanium.

If you look at the examples above you’ll notice that both sample introductions provide, qualitatively, the same information. Both explain: the goal of the experiment, which chemical principles were being studied and the experimental route taken. However, the example on the left manages to provide an introduction to the experiment without going into specific experimental details that are best left for the Materials & Methods section or the results and lines of analytical reasoning that are the domain of the Results & Discussion. The example on the left was in the correct tense and also does a better job of introducing the intent of the experiment whereas the example on the right tells the reader the authors were following instructions in a book. Also note the example on the right (second part of last sentence, “….we determined our sample was not tin….”) gives the results – save this for the discussion section. A well-written Introduction must find a balance between having too much and too little information.

3.) Materials & Methods (sometimes called “Experimental”): This is by far the most straightforward section in the body of your lab report. This section is the step-by-step account of the experimental procedures you followed. Start this section with an itemized list of any specialty glassware/equipment used and a list of known chemicals used. The procedure should not be copied from your lab manual if one is given. Write about what you actually did stating specifics, like volumes, concentrations, and names of specific chemicals used . ALWAYS: 3rd person, past tense, passive voice! Example: A total of 1.25g (0.0214 mol) NaCl was dissolved in 300 mL distilled water to make a 0.0713 M solution. Remember to write in complete sentences. When writing numbers, put a zero in front of decimal places and use the correct number of significant figures. Your procedural description should not be a five-page essay but enough detail should be given such that someone else could read this section and duplicate what you did in the lab. IMPORTANT: Do not report your data in this section; your data are reported in Results.

4.) Results: The Results section is where all data and sample calculations should be presented. Many data are individual measurements, meaning that in the body of your results you simply need to highlight it and possibly other single measurements.

Laboratory Temperature = 23.5˚C ± 0.5˚C

If there are larger sets of related data you should present them in a table with a proper number, title and legend.

Table 1: Sample Mass & Volume

Sample #

Mass (g)

Volume (cm3)

1

35.603±0.002 g

4.1 ± 1 cm3

2

25.782±0.002 g

8.0 ± 1 cm3

3

47.981±0.002 g

12 ± 1 cm3

4

19.826±0.002 g

15 ± 1 cm3

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Sample Plot

y = 1.0727 + 0.98364x R= 0.99925

Y - axis

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27.110±0.002 g

3.6 ± 1 cm3

If you note above, the data point and table (all with fabricated numbers) are presented in and around the body of the text. This is the pattern you should follow when writing your own Results section; describe the measurement/s taken briefly, then present the data. You do not need to describe the full experimental procedure you followed because that should have been accomplished in the Materials & Methods section. However, you do need to refer back to that procedure to provide the proper context for your data. Without any text to provide the proper context most data appear as just numbers on a page, devoid of their full import.

In general, the process of performing calculations on the data collected during an experiment to obtain the final results is termed data processing. In some experiments the calculations are relatively simple while in others the results are only obtained after extensive data processing. As with raw data, however, sample calculations need to be presented in the body of your Results section to provide the proper context to the numbers.

Example:

35.603 / 4.1 = 3.237

25.782 / 8.0 = 3.473

47.981 / 12 = 3.998

19.826 / 15 = 1.322

27.110 / 3.6 = 9.037 g/cm3

Example:

Density bears the units of g/cm3, which may be determined by dividing the sample’s mass by its volume. For unknown sample #1:

35.603g / 4.1cm3 = 8.7 g/cm

Presented above are two example of what sample calculations might look like. In the example on the left there are only units on the final results and with no textual reference to put the results in context; it is left up to the reader to realize they are your density calculations. In this example it is difficult to understand the example on the left without context, and it’s not hard to imagine the calculations quickly growing beyond simple boundaries and becoming too complex for even an attentive readers to follow. In the example on the right, however, the calculation is put in context, all the numbers bear their appropriate units and only one, sample calculation is presented. The full array of sample densities would be best presented in a data table such as Table 1, or in a new table altogether.

Finally, some data and results are best presented graphically and since lab reports must be typed it will be helpful to become acquainted with a program capable of graphing your results. MS Excel and some other programs offer the ability to plot data and perform linear regressions.

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y = 1.0727 + 0.98364x R= 0.99925

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Additional Points:

· When writing Chemical Equations, include phase symbols and charges.

· Number equations so that they can be referred to elsewhere in the report.

· Use Data Tables whenever you can.

· Label all data tables/graphs/charts with numbers and descriptions.

· Show statistical error calculations when appropriate.

· Use units for all numbers.

· Do not explain your results.

· Do not show every calculation of one type.

· Do not regurgitate the Experimental section.

· Do not break up tables on more than one page.

5.) Discussion: NOTE: Sometimes Results and Discussion are combined into 1 section but it should then be specifically titled “Results & Discussion”. The Discussion is by far the most important section of a lab report. In it the experimental results are analyzed and put into the context of the chemistry being studied. The theory from the Introduction, the procedures from Materials and Methods and data from Results are all drawn together to answer the question first posed to the researchers. Refer to the tables and graphs presented in the Results section! (ex: ‘As can be seen in Figure 2…’ or ‘From Table 3 it can be determined that…’) It is critical that the Discussion section lead the reader through the line of reasoning the authors used to draw their conclusions from their measured data.

Example:

Color and density are intensive and characteristic properties of metals. The color and density of several metal samples were obtained and compared to tables of known values. Since several metals share similar colors and densities their correspondence with two properties were used to uniquely identify each sample. Sample #1 possessed the typical bronze color associated with copper and the measured density was 8.68 g/cm3, close to the known density of copper of 8.92 g/cm3. This led to the conclusion that sample #1 was copper. There was significant error involved in measuring each sample’s volume, leading to a 25% uncertainty in the density. Despite this, the method followed was accurate for the purpose of determining the identity of sample #1.

Example:

The density of sample #1 was measured, and by looking at the color, it was determined to be copper. There was human error in making this decision since the color was determined by visual inspection. Color and density are important properties of metals and let you positively identify metal samples.

The example on the left is clearly superior; it addresses the chemical principles being studied in the context of the problem set before the researchers then leads the reader through the line of reasoning used to draw conclusions at the end. It also addresses valid sources of error and their probable effect on the outcome of the experiment. The example on the right is too short, lacks a clear line of reasoning and blames the experimental error on the researchers’ technique simply because they lack a more valid source of error. A full discussion, of course, would address all samples studied and sources of error in a similar fashion. If possible always compare your results to the theoretical or known values, especially if your values deviate from what you expected or if you believe your expectations were somehow incorrect.

6.) Conclusion: NOTE: Sometimes Discussion and Conclusion are combined into 1 section but it should then be specifically titled “Discussion & Conclusion”. The Conclusion in many ways resembles the Introduction. The Introduction is an overview of the entire experiment, including the goals and chemical principles to be investigated while the Conclusion is an overview of the completed experiment where you discuss whether you achieved the goals and whether your approach to the experiment was successful. The Conclusion should not repeat the points presented in the Results & Discussion, but rather tie those points together with those elements of the Introduction just mentioned. In summary, the conclusion is a very short paragraph, generally an interpretative summary, drawing conclusions about the experiment itself. How do the results relate to the initial goals of the experiment? Can alternate conclusions/explanations be drawn? If the problem wasn’t solved completely, do you have any suggestions how the experiment could be improved/refined?

Example:

In this lab, the identities of several unknown metal samples were determined. Using the properties of metals, each sample’s color was observed, and its density and conductivity measured. Upon analysis it was determined that density alone was insufficient to identify each sample and it was required to cross reference density with conductivity and color to positively identify each sample. Overall, the approach was a successful application of density and conductivity to identification of unknown metals.

7.) References: This is the final section in your lab report and should contain the bibliographic entries of any and all reference materials used in the writing of your lab report. Examples include, but are not limited to: your lab manual, textbook and reference materials found online or in the LRC.

*****This guide is meant to supplement the general guidelines for writing lab reports presented on pages 4 & 5 of the CHM 101, 113, 114 and 116 lab manual. As noted, these are only guidelines; but when it comes time for your lab reports to be graded, following these guidelines may make the difference between getting a ten, a nine, or having to rewrite it. When in doubt, ask your laboratory TA. *****

Additional tips:

· DON’T FORGET TO ANSWER THE QUESTIONS POSED BY THE LAB MANUAL!!

· Use proper sub and super scripts: It is Na3PO4 not NA3PO4 or Ca2+ not Ca2+

· Chemical names are not capitalized.

Notes:

Table 1: This table shows the masses of each sample measured with a Mettler-Toledo balance. Volumes were measured with a 100mL graduated cylinder, the smallest available.

(Present tense is OK here) (

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Fig. 1: Sample plot of a data set without gridlines and showing the linear fit to the data.

When and how you plot data depends on the type of data as well as how you intend to use the results of your graph. The sample plot to the right shows the generally accepted format for plots and graphs. The axes must be labeled with the values being plotted and the linear (or polynomial fit) to the data should be displayed somewhere on the plot. There should also be no gridlines.