Combustion Reactions
Written for PULSE by Christopher Martin
Edited By: Stephanie Nardei
Time:
2 class period
Preparation
none
Time:
Materials:
Abstract
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.
Objectives
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 Standards:
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
Activity
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;
H2 +O2  H2O
C +O2  CO2
CH4 +O2  CO2 + H2O
C8H18 +O2  CO2 + H2O
C2H6 +O2  CO2 + H2O
4. 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.
5. 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.
6. 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.
7. 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?
8. What are the impacts of sulfur and nitrogen oxides in the atmosphere?
9. For homework students should practice balancing equations An exhaustive list of
problems can be found at http://dbhs.wvusd.k12.ca.us/webdocs/Equations/WSBalancing.pdf . This can be completed for homework
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
Homework
Balancing equations.