MHS Chemistry
Calculations - Rules & Advice
 
When writing a lab report, keep in mind that you want to report what you did as clearly as possible. The General Lab Rubric describes all the sections and the order in which they should appear, but this page is a more detailed description of how to present calculations.

1. First of all, don't be afraid to take up lots of room. Make them super easy to read by spreading them out.
2. Don't be afraid to type them, but calculations are often easier for a student to present well by hand. If you decide to type them, use of decimal-aligned tabs or courrier font can help presentation.
3. ALWAYS describe what you are doing in words or equations. One way is to use descriptive sentences in two columns (click here for an example). I will be expecting a specific format that should serve you well in any class you take; but of course your current teachers' preferences should always be respected. Here are my preferences (hint hint):
   1. additions and subtractions should always be "stacked" and each line should include the description and label of the number too for example:
      
        mass of beaker and gall bladder              373.96   g
      - mass of beaker                             - 126.11   g
      = mass of            gall bladder            = 247.85   g
      
      
   2. multiplication and division should always be shown like multiplying fractions:
      
        D = m  =  23.16 g   =  4.1 g 
            V      5.7  mL         mL
      
        q = mDTCp = (23.16 g)(6.6 C)(0.84 cal) = 130 cal
                                          gC
4. Notice that besides every number having a label (like "g") and a name (like "mass of ..." or "V"), the decimal points are lined up whenever possible, and the answers are reported with the proper number of significant figures.
5. If you have a lot of calculations that are the same, you only need to show the first set in detail as a sample calculation. For the rest, just summarize the results. For example, if you have to calculate 10 different densities in the same way, just show the first one (as above), then present all ten in a results table.
6. Finally, if you ever have any questions, ask yourself this: is it completely clear and completely correct? Because you should ask your teacher if you have any questions, and your teacher will answer with those two thoughts in mind.

If you decide to type your lab reports, I have written a lab without any content and put it on the web site at zahm.org/mhs/common/sample.doc. It is a Word 2000 document that has all the general sections of a lab formatted, including the calculations section. Try it out!

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