About Combustion

About Combustion


Energy and energy transformations are everywhere, all around us and inside us, and it is energy transformations that make things happen. Energy takes many different forms, such as potential and kinetic, solar, thermal, chemical, electrical, and nuclear, as well as heat and work. In this E-sheet, we will explore how energy changes during one process in particular—combustion.

In this lesson, you will read about what happens to energy when heat is produced in a combustion system, as in a car engine.


Go to and read How Car Engines Work: Internal Combustion. Study the illustration of the engine parts so you understand how combustion works in a gasoline-powered engine. While you are reading, look for the answers to these questions and write them down on your About Combustion student sheet:

  • Why is a car engine an internal combustion engine rather than an external combustion engine?
  • What are the four strokes in the combustion engine in this article?
  • Describe how these four strokes work.

Now go to Energy: The Quick Tour to further explore how energy is transformed in internal as well as external combustion engines. As you read, think about the answers to these questions and write your anwers on your student sheet:

  • What is it in the combustion process that causes gas to expand?
  • How does the transformation of energy into mechanical energy in a car engine differ from the transformation of energy into mechanical energy in a power plant, which is an external combustion system?

Now go to The Conservation of Energy and the First Law of Thermodynamics. While reading this article, think about the following questions and write down the answers on your student sheet. Come to class prepared to discuss the answers:

  • What is the first law of thermodynamics?
  • Where does the energy from the combustion process go?

A combustion reaction is a chemical reaction. To see how the chemical reaction works, go to Combustion Reaction and click on the play button.

  • What is happening in this chemical reaction?

This esheet is a part of the Combustion lesson.

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