Combustion Reactions

Written for PULSE by Christopher Martin
Edited By: Stephanie Nardei

Time: 2 class periods


Materials: --

Students need to understand how carbon dioxide is formed when fossil fuels are burnt; when they react with oxygen. It is also fundamental to chemistry that the students understand the law of conservation of matter, and can balance equations. The study of the environmental risks caused by burning fossil fuels and the fundamental concepts of chemistry combine to provide an interesting learning opportunity for the students.

Students will be able to:

  1. Write a balanced chemical equation.
  2. Articulate how burning fossil fuels increase the carbon dioxide levels in the atmosphere.

National Science Education Standard
Content Standard D : The Physical Setting
The structure of Matter

The configuration of atoms in a molecule determines the molecule's properties.

Strand 5: Physical Science
Concept 4: Chemical Reactions
Investigate relationships between reactants and products in chemical reactions.
PO 3.
Represent a chemical reaction by using a balanced equation.

Teacher Background
Coal, oil and gas are fossil fuels. They were formed from fossilized plant and animal remains. Most of the energy we use is produced by burning fossil fuels. When coal, oil and gas are burnt, they react with oxygen to form water and carbon dioxide. The percentage of carbon dioxide in the air is increasing, and with more carbon dioxide our atmosphere acts as a greenhouse, retaining heat that would otherwise reflect into space. The observed increases in global temperatures, from Antarctica to Canada is known as global warning.

Fossil fuels are hydrocarbons, primarily coal, fuel oil or natural gas, formed from the remains of dead plants and animals. The theory that hydrocarbons were formed from these remains was first introduced by Mikhail Lomonosov in 1757. In common dialogue, the term fossil fuel also includes hydrocarbon-containing natural resources that are not derived from animal or plant sources. These are known instead as mineral fuels. The utilization of fossil fuels has enabled large-scale industrial development and largely supplanted water-driven mills, as well as the combustion of wood or peat for heat.

The development of the law of the conservation of mass can be found at http://dbhs.wvusd.k12.ca.us/webdocs/Equations/Conserv-of-Mass.html.

Extra help on balancing equations can be found at http://dbhs.wvusd.k12.ca.us/webdocs/Equations/Equations.html

Related and Resource Websites
EPA on Climate Change http://www.epa.gov/climatechange/index.html
Fossil Fuel: http://library.thinkquest.org/17531/fossil.html
Fossil Fuels on Wikipedia http://en.wikipedia.org/wiki/Fossil_fuel



  1. Students are introduced to the Law of Conservation of Matter; matter is conserved.  On the board or overhead display the equation represents the combustion of octane.  Explain to the students that the number of chemical elements on the left side of the reaction (reactants) is equal to the number of chemical elements on the right side of the reaction (products).  Together balance the equation. Using the information on What is a Chemical Equation http://dbhs.wvusd.k12.ca.us/webdocs/Equations/Meaning-of-Equation.html, review what a chemical equation represents. 
  2. Explain to students that it is not enough to just put the chemical formulas for each reactant and product on either side, the chemical equation also informs them of how much of each, or the ratio that is needed for a balance reaction. Using the information at http://dbhs.wvusd.k12.ca.us/webdocs/Equations/Balance-Equation.html review balancing equations with your students.
  3. Once guided through how to balance an equation students will work together to balance the following hydrocarbon combustion reactions which represent fossil fuel burning;


  1. The class should discuss successful methods of balancing equations. Students may have different techniques to balance equations.  It is useful to allow them to create a method.
  2. Students have now been introduced to some of the main combustion products of fossil fuels, but Sulfur and Nitrogen are also found in coal and oil as impurities. When these react with oxygen they form oxides which are acidic when mixed with water, causing acid rain.
  3. Students should use text books and computers to find balanced equations for the combustion of sulfur and nitrogen, and to link with the previous work on nuclear power they should identify the balanced equation for the fission of uranium 235.
  4. As students balance the equations for the combustion of fossil fuels what do they notice about the product of this combustion reaction?  Where do these products go?  How do they alter the environment that they enter?  Is increasing the carbon dioxide in the air a problem? Explain to the students that the scientific evidence suggests that increased carbon dioxide will lead to climate warming.  Students may have seen the documentary movie, an inconvenient truth, which presents a clear explanation of the relationship between carbon dioxide and climate change.  You can also download a series of podcasts from the University of Arizona that deal specifically with global climate change.  ADD SPECIFIC DETAILS.  Following this discussion ask the students what percent of the atmosphere currently is carbon dioxide? How does our continued use of fossil fuels effect the carbon dioxide composition of the atmosphere?  What is it about the chemical nature of carbon dioxide that results in this change?
  5. What are the impacts of sulfur and nitrogen oxides in the atmosphere?
  6. For homework students should practice balancing equations An exhaustive list of problems can be found at http://dbhs.wvusd.k12.ca.us/webdocs/Equations/WS-Balancing.pdf . This can be completed for homework

Not Applicable.

Embedded Assessment
Students can be informally assessed as they participate with their peers to balance equations and discuss the impact of sulfur and nitrogen oxides. It may be necessary to test specific knowledge or to set homework so that students can practice this new concept. As students balance the fossil fuel combustion equations and identify the products of they can be assessed on identifying what impact combustion has on the atmospheric co




PULSE is a project of the Community Outreach and Education Program of the Southwest Environmental Health Sciences Center and is funded by:

NIH/NCRR award #16260-01A1
The Community Outreach and Education Program is part of the Southwest Environmental Health Sciences Center: an NIEHS Award


Supported by NIEHS grant # ES06694

1996-2007, The University of Arizona
Last update: March 7, 2007
  Page Content: Rachel Hughes
Web Master: Travis Biazo