The Laboratory Write-up

There are two primary functions of the lab write-up:
  1. To communicate the experimental work you have done and your results.  Readers may include:
    1. Classmates -- who may be interested in comparing their own results to yours.
    2. Your teacher -- who will be interested in evaluating your performance of the lab and your level of understanding.
    3. Fellow researchers -- who may want to reproduce your results for themselves.
  2. To keep a record for your own future use.  One day you may wish to refer back to or repeat a lab.
In order to accomplish these your write-up needs to be accurate, complete and understandable.

The Style of the Write-up

In most college lab work, and in all professional lab work, the standard style is third person, passive voice.  So, one does not write, "I poured the water from the 250 mL beaker into the erlenmeyer flask," but instead,"the water was poured from the 250 mL beaker into the erlenmeyer flask."  This is not a very compelling way to write and it is not a very enjoyable style of writing to read.  I will normally accept your write-ups in a more chatty first person, active voice but will occasionally ask you to try your hand at the standard style.

The Format of the Write-up

Your write-up should almost always contain the following sections:

Header:  Where you will write the lab title, the date the lab was performed, your name and your lab partner(s)'s name(s).

Purpose: Your scientific reason for performing the lab.

Theory:  The theoretical foundations of the lab.  This should include any formulas (with all variables clearly defined) used in the calculations based on the data; and any predictions expected for the results.

Apparatus: An equipment list for the lab.  This should  include manufacturer names and serial numbers where possible.

Procedure: A step-by-step guide to what you did in the lab and how you did it.  This is one of the most important sections of the write-up.  If you goofed up in performing the experiment you, or someone else, should be able to find out how by reading this section.  You need to write this section up AS YOU ARE PERFORMING THE LAB to ensure that it is an accurate and full representation of what you actually did.  You must especially include any steps you took that differed from those in the suggested procedure in the lab book, or that I may have given you.

Data:  The measurements that you actually took.  So, if you measured the diameter of a circle in order to calculate its area using the equation A=pr2 you would enter the diameter measured, but not the calculated radius or area,inthe "Data" section.  You will find write-ups where the data and calculations are included in one section, but you must always remember to distinguish between the two things.

Calculations:  The calculated values based on the data.   Include any  graphs and the results derived from them in this section.  Results  are usually given in MKS units.

Conclusions:  A statement of the final calculated results and whether they agree or not with the expected values given the estimated precision of the measurements.  You should also make statements regarding  the  limitations of the techniques and instruments used to perform the lab and  how you would go about improving them to increase the precision and accuracy  of the results.      

Sample Write-up

Measuring the Area of the Front Cover of a Textbook,   August 21, 2003, Krusty the Klown
                                                                                             Lab Partner: Sideshow Bob

Purpose: to find the area of the front cover of a textbook by measuring its length and width.

Theory: For a rectangular object the area, A, can be calculated from the length, l, and width, w, using the formula A=l×w.

Apparatus:  Tajima steel ruler, model number 1050.

Procedure: The steel ruler was placed along the long edge of  the book to ensure that length measured was at right angles to the width  dimension.  The zero point of the ruler was lined up along the left  edge and the reading taken from the right edge.  The width was measured  similarly.

Data: The length and width of the text were measured as: l = 25.8  cm  = 0.258 m
                                                                                         w = 20.6  cm =0.206 m


Calculations: The area of the text is A= l×w =  0.0531 m2

Conclusions:  The area of the text is 0.0531 m2 .

Marking Rubric:

Labs can receive a mark up to 10. The marks are distributed according to:

Presentation: A well-presented lab using the format above with the information complete and correctly placed will receive 4 marks. One that misses a minor section (header or apparatus) or is somewhat confused or incomplete will receive 3 marks. One that misses a major section or that shows significant confusion or incompleteness will receive 2 marks. One that misses more than one major section or misses or confuses much essential information will receive 1 mark.

Data: A lab with complete and well-taken data will receive 2 marks. A lab with significant omissions or poor quality data will receive 1 mark.

Calculations and discussion: A lab that has complete and correctly calculated results with appropriate discussion will receive 4 marks. A lab that is complete but with the occasional error or omission in calculations and discussions will receive 3 marks. A lab with a major omission or omissions and incoherent or significantly incomplete discussion will receive 2 marks. A lab lacking discussion and/or calculations will receive 1 mark.

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