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How to write up a practical

Before you begin your write-up, develop a check-list of requirements for the practical and make sure that your submission meets every one.  You need to make sure that every question which you have been directed to address has indeed been addressed.  Go through the check list with the piece of work in front of you before you submit.

In scientific reporting, truth is of the highest importance.  The truth, the whole truth and nothing but the truth, is always required.  Even a tiny detail, if it is mis-stated, casts doubt on the whole document.  Never claim as your own, work which is someone else's.  If you don't attribute such work, you are implying that it is yours.

The default font supplied by Word is probably not best for a scientific report.  I recommend "Times New Roman". A good report is short and to the point.  A conversational style is not appropriate.  A dry detached style is your goal.  Avoid unnecessary words.  Do not repeat yourself.  The words, "as I said before" should never appear. 

Two general requirements are

  1. Your write-up must display understanding of what you have been doing. 
  2. Your use of English must be clear, concise and grammatical.
  3. You are doing chemistry, so reactions must be described by means of chemical equations, and the chemical formulas of substances must be included where appropriate.

The sections suggested below are flexible: depending on the nature of the experiment, the method, results, discussion and conclusions sections may be grouped together.  For example, the method section might be grouped with the results section as "Method & Results".  In another case, a "Results & Conclusions" section might be more appropriate, and so on.


Start with a good title.  It should express the aim of the experiment (and so there is no need for a separate "aim" statement). The title given in the handbook may not be the best title for your report, since it serves a different purpose.  Use the "heading 1" style.


The first section is the introduction. Use the "heading 2" style.  Set your experiment in context with a little theoretical background.

Apparatus & Materials

List the items of apparatus and the chemicals and solutions that you used.  Include the capacity of each piece of volumetric apparatus, as well as beakers and flasks.  Always state the concentration of a solution (if known), (except in the case of indicator solutions, which are made up according to standard recipes, usually 0.1%w/v, in water or a mixture of alcohol and water).  Include diagrams in this section.  However, only include a diagram when it adds something to your report.  If standard apparatus is used in standard ways, no diagram is necessary.  Taking good photographs is not easy.  Be very careful about incorporating them in your write-up.  Usually a good diagram is much better.


Briefly describe any hazards that the materials, apparatus, or what is to be done with them might involve.  Mention fire, explosion, and toxicity hazards etc. in clear prose.  If there are no special hazards, you can leave this out.  Explain any symbols or abbreviations.  (This latter is generally true.)


Write clearly what you actually did (past tense), making clear any deviations from the schedule. "The contents of flask A were added to the contents of flask B" or "we (or I) added the contents of flask A to those of B" are acceptable forms.  Forms such as, "Add the contents of flask A to flask B" are not acceptable.


The next section is the results section.  Set out your raw results clearly in tabular form.  This section also includes the processing of your results, including all calculations, and any graphs you produce.  Calculations must be explained.  Chromatograms, or diagrams representing them, would be included here.  If you include results from other students, you must attribute them.  (Give the surnames and initials of the students involved.)


Set your results in context and discuss any meaning that can be extracted from them.  If you feel that there were obvious sources of error, mention them here.  Confine your attention exclusively to your own work in this section.


What conclusions can you draw from the results of your experiment?  Your focus must be very narrow.  You must not make statements which are not directly connected with your experiment.  You might, for example, give the rate equation you have deduced from your experiment.


What students do wrong

1.    You must report what you did.  That rules out, "Pipette 5ml..." or "Add solution A to solution B..." You have to say, "5 ml were pipetted..." or "Solution A was added to solution B..."

2.    When you borrow results from another group, as you may sometimes do, you must say so, and say who they came from.  For example, "The value of n was obtained from the work of N. Greene and M. Sanders..."

3.    When it says, "Plot A against B," it means A is on the vertical axis.

4.    All observations, calculations, working and graphs must be in the Results section.

5.    The report must be a consistent and orderly body of work.  It should be arranged logically in proper order.  It must not contain irrelevant material such as photocopies of inappropriate passages.

6.    Chemical equations and formulae require subscripts and superscripts.  Learn how to do them or use names.  E.g.. S2O82- is not good, learn how to do S2O82-.  Keyboard shortcuts in Word are "ctrl + =" for subscript and "ctrl + shift + =" for superscript.  HTML uses the tags <sup> and <sub> with </sup> and </sub>

7.    The Conclusions section should consist of your conclusions only and must not contain calculations.  Conclusions must be based exclusively on the experiment you have performed.  You must make sure that you include the conclusions that the practical requires. Include nothing which is not clearly demonstrated by the experiment you have carried out.  Students tend to include general statements of theory which their experiment does not provide any evidence for.  This is very bad.

8.    Don't mix up cm with cm3.

9.    All calculations must be fully explained, though briefly.  The origin of any values stated must be described.  For example, "The value of m was obtained from the slope of graph 1" and then go on to say how it was obtained.

10.    The work must commence with a title.  The word "title" should not appear.  The aim of the experiment is best not stated separately.  It should form part of the title.

11.    On a graph, you must show all your points.  In scientific graphs you should never simply join points.  Instead you should draw the line suggested by theory, which should pass close to all your plotted points, but perhaps not through any of them.  This is the line of best fit.  Usually it is a straight line, a trend line in Excel-speak.