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Chemical History of the Candle

Lab Assignment 4: Identifying the Products of Combustion

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LAB: The Products of Combustion

Students taking Scholars Online AP Chemistry in the fall should consult with the instructor for additional AP lab instructions to use for this experiment.

Goal: To demonstrate that water is a product of combustion

Materials:

Procedure:

  1. In the instructions below, remember that you do not want to actually funnel the melting icewater from inside the funnel into the test tube. You want to capture only the water which condenses on the OUTSIDE, and which comes from the candle vapor and possibly the atmosphere.
  2. Line the glass funnel with aluminum to provide insulation for the ice and to keep melting icewater from reaching the test tube!
  3. If you do not have a glass funnel, use several layers of heavy aluminum and wrap a small glass jar carefully.
  4. Mount the glass funnel or aluminum cup so that any liquid on its outer surface will drip into your test tube or other collector AND so that you can position your candle beneath it.
  5. Be sure that the collector is clean and dry.
  6. Place some ice cubes (count and record the number) in the funnel and allow the entire aparatus to sit without lighting the candle for 2-3 minutes (record the time).
  7. Measure the amount of water which condenses from the atmosphere alone and drips into the test tube. If necessary, simply measure the depth of the water in inches or centimeters and don't worry about the precise volume.
  8. Dry the test tube and replace it in position beneath the funnel aparatus.
  9. Dump out the ice and melted water from inside the funnel, and replace it with the same number of ice cubes you used the first time.
  10. Light your beeswax candle and hold it so that its vapor collects and condenses along the bottom of the funnel for the same amount of time as before.
  11. Determine the amount of water in your collector, using the same technique as you used for water from the atmosphere alone.
  12. Repeat the experiment with your parafin candle, and if you have another flame source such as a small oil lamp, with that as well.
  13. Record your information in a table, like this:
Trapping flame products
 Trial type  Amount of water collected  (Amount of water collected) - (amount of water collected for no candle)
No candle   0
 Beeswax candle    
 Parafin candle    
 Other fuel    

Report:

As usual, describe your actual apparatus and procedures. You may substitute any safe method of collecting the condensation -- but be sure to clear your procedure and materials with the adult who is responsible for providing your lab supervision.

Present your results in an orderly fashion--you decide the best way. Include your thoughts on the following questions:

  1. Why do we subtract the atmospheric condensation from the condensation provided by each candle?
  2. Which of your candles produces the most water?
  3. What do you think this indicates about the composition of the candlewax?