candle (1K)

Comments on Lab Reports
for Observing a Candle

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


When you complete your work on this lab you will be more aware of the process of observation and able to answer the following questions based on your observations:

  1. What happens to the candle when you light it?
  2. Does the candle need oxygen in order to burn?
  3. Can you prove that the candle produces carbon dioxide when it burns?
  4. Can you prove that the candle produces water when it burns?
  5. What happens when you hold a non-flammable object in the flame and what is the identity of the substance you collect this way?
  6. Is it possible to light a candle without touching the flame directly to the wick? Why or why not?

For this lab write answers for each of the questions. The answer to each question should describe your experiment and your conclusions. Describe the experiment by stating what you were trying to find out, what you expected to happen, and what in fact did happen. Use your actual observations to support your conclusions. As much as possible you should present quantitative measurements (made with a lab balance, ruler, thermometer, etc.). This may not be possible but carefully controlled experiments and qualitative descriptions of your results are expected.

You will be graded on the quality of your writing, the profesionalism of your work’s appearance, the design and execution of your experiments and the degree of your understanding of the underlying science.

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 report is too long: eliminate unnecessary details, eliminate redundancy, use more concise language, make sure everything you write means something.
  5. You clearly understand the underlying science.
  6. It is not clear whether you understand the science.
  7. This was not written according to the given lab report format.
  8. Incomplete—see me for details.
  9. Steam and fog/condensation are not identical. Steam is gaseous water which is above 100°C (212°F). Fog/condensation is liquid water in tiny droplets suspended in air or collected on a surface.
  10. Soot is not carbon dioxide. Soot is made of tiny particles of solid pure carbon—much like charcoal or graphite. Carbon dioxide is a compound made of carbon and oxygen (CO2). It is an invisible gas.
  11. The report has a professional appearance.
  12. The report is acceptable in appearance but has some flaws.
  13. The report is messy, hard to read, or shows signs that little or no care was used in writing it.
  14. Be careful that your evidence is relevant to your conclusions.
  15. The candle does not produce oxygen, it uses it in order to burn. The oxygen comes from the air, which is about 20% oxygen. Carbon and hydrogen are the elements the candle is made of. Carbon combines with oxygen from the air to make carbon dioxide. Hydrogen combines with the oxygen to make water. Oxygen is not flammable.

This document refers to the lab that can be found here.
Last updated: Oct 31, 2007             Home