How and Why Things Burn: Teacher's Notes

Activity: Thinking About Combustion

Safety: First and Foremost

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Objectives

National Science Education Standards: Content Standards

This activity fulfills the following within the Content Standards: 9-12

Materials

Method

Questions

  1. Water is often used to put out a fire. Using the combustion triangle, why should this work?
  2. You're frying catfish in a pan on the stove and turn your back for just a moment The fish and oil in the pan catches fire. Will placing the lid on the pan put the fire out? Explain using the combustion triangle.
  3. Explain the molecular scale changes (or stages) that take place when your pan of catfish catches fire.
  4. Explain the macro scale changes (or stages) that you would observe when your pan of catfish catches fire.
  5. It has been stated that wood going to the combustion products of carbon dioxide and water is thermodynamically favorable. What does this mean? Why is this true?
  6. If wood going to the combustion products of carbon dioxide and water is thermodynamically favorable, why doesn't wood spontaneously catch fire?

Extensions

  1. Have the students think about the processes when a volatile liquid like gasoline burns.
  2. Can you boil water in a paper cup over an open flame? Why or why not?
    NOTE: You can do this extension as a demonstration or the students can do it.
  3. Magnesium metal will burn in carbon dioxide (dry ice). How is this possible? (Have the students revisit the fire triangle.) The students can view a video of this demonstration at:
    http://jchemed.chem.wisc.edu/JCESoft/CCA/CCA0/MOVIES/MAGCO2.html
    This link to the Journal of Chemical Education includes references and safety information for this demo, as well as further discussion and questions for the students.

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