Comments on Lab Reports
for the Soda Straw Balance

A reminder of the objective and grading criteria given in the original handout.

Objective

In this lab you will build and use a super-sensitive balance made from ordinary materials.

For success in this lab you must make a working scale that is accurate—that is, measurements get repeatable results when done by different people. You must also include a neat, easy to read data table which shows the mass of the objects you weigh in square centimeters of paper and in grams. Finally, you must answer the following questions:

  1. When someone who is not your lab partner measures the mass of an object that you measured do they get the same result? Why or why not?
  2. What could you do to improve the accuracy of your balance?
  3. What are the upper and lower limits on the masses you can measure using your balance?
  4. Which lab partner has heavier hair? That is, for the same length of hair from each partner, whose has the higher mass? By how much?
Grading

Write a brief report (4 - 6 paragraphs) describing what you did. Provide your measurement results in a table. Answer the questions fully: each will require one or more paragraphs of good writing.

You will be graded on the quality of your writing, the profesionalism of your work’s appearance, the utility of your lab balance, and the repeatability of the measurements you make with it. Consideration will be given to creative designs.

The following comments may or may not apply to your paper. I have noted on your paper numbers corresponding to the numbers next to each comment below. If you intend to do a second draft (a do-over) then pay particular attention to these comments. If you do not need to do a second draft, or do not want to, then pay attention to these comments anyway: they will help you to do well on your next assignment.


  1. For each question you should have written one or more well-written paragraphs. Using your best writing tell what you did, what you observed and what it means.
  2. You need to connect your conclusions to your observations. Use evidence to justify conclusions—not prior knowledge.
  3. Your writing is good: clear and precise.
  4. Your writing needs to be more clear and precise. Leave out unnecessary details and be careful about redundancy. Avoid it.
  5. Your clearly understand the underlying science.
  6. It is not clear whether you understand the science. See me.
  7. This appears to be lab notes, not a report. It should be a report and represent your best writing.
  8. Be careful that your evidence is relevant to your conclusions.
  9. The report has a professional appearance.
  10. The report is passable but could be better organized and/or more legible.
  11. The report is messy, hard to read, or shows signs that little or no care was used in writing it.
  12. All numbers must be reported with a reasonable number of digits (significant figures) and include units!
  13. Data table is missing, incomplete or incorrect. Data tables should be easy to read. Units go with the heading of each row or column. Use borders to define the table.
  14. The upper limit of the scale is the mass above which you cannot measure. Think of a measuring cup: it cannot be used to measure volumes bigger than itself. The lower limit of the scale is the mass at which the balance cannot be relied upon to move at all. The lower limit can also be defined in terms of the smallest weight you can reasonably manufacture (1/8 cm2, perhaps).

This document refers to the lab that can be found here.
Last updated: Jul 29, 2007             Home