Complete and Incomplete Combustion

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The Products of Combustion

When fuels react with oxygen in the air, they burn and release large amounts of energy in the form of heat and light. The amount oxygen available affects whether a fuel will undergo complete or incomplete combustion. For a fuel to undergo complete combustion, plenty of oxygen must be present in order to make the products carbon dioxide and water. If there is insufficient oxygen then the fuel will undergo incomplete combustion, producing carbon (a black powdery solid also called soot), the poisonous gas carbon monoxide and water.

Complete and Incomplete Combustion Lab, Complete and Incomplete Combustion Worksheet

Complete and Incomplete Combustion Learning Objectives:

  • To test for the products of combustion
  • Identify complete and incomplete combustion.

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Incomplete and Complete Combustion Lab Materials

  • Tea light candle
  • Ice
  • Cold water
  • Lime water
  • 250ml beaker
  • 2 boiling tubes with a rack
  • 2 double-holed rubber stoppers
  • Lighter or matches
  • Retort stand and clamp
  • Glass funnel
  • Glass tubing
  • Pump


  • Safety glasses must be worn for the whole activity.
  • Limewater is an irritant.

Complete and Incomplete Combustion Lab Procedure:

  1. Setup the equipment as shown in the diagram below.
  2. Light the tea light candle and carefully position it under the funnel.
  3. Start the pump.
  4. Record observations in the space provided.

Complete and Incomplete Combustion Lab, Complete and Incomplete Combustion Worksheet

Post-lab Questions:

  1. Name the product formed in first boiling tube.
  2. Name the product formed in the second boiling tube. How can you confirm the presence of this product?
  3. Name the fuel in this experiment.
  4. Is this experiment an example of complete and incomplete combustion? Give a reason for your choice.
  5. Are there any other observations (e.g., residue present or absent) which confirm your answer in question four?
  6. If the tea light candle was placed in an enclosed chamber instead of under a funnel and the test was carried out again, what would you expect to observe?

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