Formal Report for the Atomic Absorption Lab
The report should be 3 (min) to 6 (max) double-spaced pages (including graphs and figures) using 12 pt Times New Roman font on 8.5 x 11 inch paper. If graphs and figures are included, they should not take up more than a total of one page in all. Cover pages, which are not required, do not count toward the page total. The report will be worth 10 laboratory points. The report is due May 7th.
The purpose of formal report is to
describe the analysis of your tap water
sample. You could think of it as a report to a client that has hired
you to analyze their water for Ca2+, Mg2+, and F-.
There normally is a fair amount of freedom in how such technical reports are
organized. However, to make it easier for us to compare different
reports, we request the report to have the following parts:
1. An Introduction. You should indicate the purpose of the report and include a brief discussion of what affects Ca2+ and Mg2+ concentrations in Sacramento and surroundings. Also, you should indicate why it is of interest to know the concentrations of Ca2+ and Mg2+. You can also use information in the class website or other sources to discuss water quality. You also should indicate why it would be useful to know F- concentrations and how F- gets into tap water (see the Chem 31 Lab Manual – Ion Chromatography section for further information). You may be able to find information on expected F- concentrations from a water agency.
2. An Experimental Methods section. This should include a brief description of how the atomic absorption spectrometer (AAS) works and the methods you used to analyze the samples. It is important that the description of the instrument is accurate. Although we will not be covering the functioning of the instrument in the lecture, you should have information on how the instrument works from lab lectures, the lab syllabus, and from the Harris text book (see Chapter 20). When writing a description of the methods, the focus should be on the main steps that you took. This should include how standards were prepared, how the tap water sample was diluted, and how samples were analyzed. It is not helpful to restate the procedure in the lab syllabus. For example, writing "we calculated the dilution factor necessary to produce four Mg2+ standards into the 0-1.0 ppm range") does not tell the reader what dilution was used or, more importantly, the actual Mg2+ standard concentrations or range of Mg2+ standard concentrations. This section does not need to be highly detailed. For example, a detailed list of operational parameters of the AAS, including slit widths and flow setting, is not needed.
A short paragraph should explain how
the IC functions (this is also described in Chapter 25 of the text) and how the
one point calibration for F- was used.
3. A Results/Discussion section. This section should include the tap water Ca2+ and Mg2+ concentrations, a discussion of the quality of the results, and a discussion of what the concentrations mean in the context of other measurements. To indicate the quality of the measurements, you may want to discuss the calibration curves that you produced, the uncertainty in the tap water concentrations, and the error in the unknown measurement (this should be available when the non-formal AA lab report is returned). A discussion of the meaning of the tap water concentrations normally will also include a comparison to measurements from other samples collected in the vicinity, if possible, and/or from other samples of similar concentration. Data from several past classes is available on the web-site and an Excel Spreadsheet containing this semester's data may become available. Compare your tap-water with other samples from your own area if possible, and from other areas as well. Note that some seasonal variability is expected so that a 20% difference, for example, from a water agency or class median value, not at all unexpected. Further variation is possible in drought years.
For the fluoride analysis, you should describe whether you think F- is added to water, if F- is naturally present, or if F- is not detectable (no observable peak). You also can compare your results with reports from water agencies which may list if water is fluoridated.
Important Caution: If you take specific information from sources such as the Harris textbook (as mentioned above), they should be referenced. You should try to write descriptions in your own words. Copying whole sentences or phrases from other sources without putting them in quotations is considered plagerism (a form of cheating by stealing someone else's writing). You are welcome (in fact recommended) to work with others provided you are doing the writing yourself. A positive way to work with another is to exchange completed reports and proof-read each other's reports. Students found to have major parts of the report written identically to others may be considered to have plagerized their reports.
Half of your grade for this report will be based on the clarity and grammar. This means that the reader should be able to follow and understand what you are trying to say. Also, it should be said in a grammatically correct way. This means proper spelling, punctuation, and sentence structure. It is recommended that you and a classmate exchange reports to proofread. The rest of the grade will be based on the completeness and general content of the report (inclusion of parts listed above).