Download de Caux - Combustion of Methane Demonstration

Dakota de Caux
November 24, 2014
Activity: Combustion of Methane
Curriculum/Learning Context:
Grade 10 – Science
Chemical Reactions Unit
 CR1 Observe common chemical reactions in your world
o Observe and describe chemical reactions that are important in everyday life.
o Perform activities to investigate exothermic and endothermic chemical
reactions.
o Show concern for safety and accept the need for rules and regulations.
 CR3 Identify characteristics of chemical reactions involving organic compounds
o Observe and describe the combustion process.
o Illustrate, using chemical formulas, a variety of natural and synthetic
compounds that contain carbon.
This demonstration targets two of the outcomes within the chemical reactions unit of
Science 10. It would probably be the most beneficial to use this demonstration once students had
a basic understanding of hydrocarbons, exothermic reactions, and the combustion process. It is
also effective at grabbing the attention of students and could be used as an introduction to the
chemical reactions unit.
Grade 11 – Physical Science
Foundations of Chemistry Unit
 PS20-FC1 Predict products of the five basic types of chemical reactions and evaluate
the impact of these reactions on society and the environment.
o Observe & analyze combustion reactions (S,K)
o Describe the effects of specific chemical reactions that affect the environment
(K, STSE)
Heat Unit
 PS20-HT2 Determine experimentally the quantities of heat involved in chemical
reactions.
o Distinguish between endothermic and exothermic chemical reactions (K)
o Analyze and compare the fuel consumed and heat energy output of various
combustion reactions involving common fuels (e.g., methane, propane,
octane, and ethanol). (STSE, S)
Since this demonstration fits into both of these units for Physical Science 20, it could be
used as a summary for the foundations of chemistry unit and an introduction to the heat unit. The
demonstration could also be done more than once during the course. It could be used during the
chemistry unit to demonstrate a combustion reaction and then repeated during the heat unit to
demonstrate the exothermic properties of the combustion of methane.
Materials:
 Methane Gas (Valves in the lab)
 Rubber Hose
 Beaker, Erlenmeyer flask, or large plastic tub
 Dish soap
 Large glass beaker filled with water
 Candle & matches
 Safety glasses
Procedure:
Demonstration
1. Collect all of the required materials and position near the gas valve that you plan on using
2. Combine dish soap and water to produce the soap solution within the desired container
(beaker, Erlenmeyer flask, or large plastic tub). A 3% detergent solution is recommended
(ex. ~9 mL of dish soap with 290 mL of water). The solution should produce bubbles
readily to ensure that the natural gas is being contained.
3. Attach the rubber hose to the gas valve and submerge the other end in the soap solution
4. Pre-light the candle and position an arm’s length away from the soap solution
5. Wet hand by dipping it into a large beaker of water. Use this hand to hold the bubbles.
6. Turn on the gas and allow bubbles of methane to form until a large handful can be easily
collected
7. Hold hand straight out and as far from your body as possible. Students should be
instructed to hold still during the reaction.
8. Touch the flame of the candle to the bubbles to initiate the reaction.
9. Repeat several times
10. Dispose of the soap solution down the drain and ensure that the main gas switch gets
turned OFF.
Discussion
1. Ask students to be looking over the discussion questions during the demonstration and
jotting down their observations
2. Once several students have had a chance to participate in the activity, lead a class
discussion using the questions from the handout
Safety Concerns:
 This demonstration requires individuals to be in close proximity to an open
flame/combustion reaction
o Long hair should be tied back
o Loose clothing should be removed or secured; sleeves rolled up
o Jewelry should be removed
o Safety glasses should be worn at all times
o Hand holding the gas containing bubbles should be wet during the reaction
o Fire extinguisher should be on hand
o It should be confirmed that the fire suppression system will not be set off by this
combustion reaction
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The use of natural gas valves also present a potential safety concern
o Methane gas is highly flammable
o The valves should be checked for leaks and the master switch should be off
before and after the demonstration
o If bubbles are not being produced, gas will be accumulating in the solution and
may be released into the classroom air. The scent of natural gas should be
detected.
o Ignition source should be positioned away from the gas valve and the soap
solution.
The soap solution can contain high concentrations of methane gas after several
demonstrations
o Special care should be taken to ensure that the solution is not exposed to an
ignition source.
o The solution can be poured down the sink for disposal.
Students will be wetting their hands before handling the methane bubbles. This can result
in some moisture being dripped on the floor and the creation of a slipping hazard.
Science:
Hydrocarbons are organic compounds composed solely of hydrogen and carbon atoms.
Combustion is the reaction of a substance with oxygen to produce oxides, light and heat. Most
combustion reactions involve organic compounds.
The combustion of methane is an example of an exothermic reaction. More energy is released
when the bonds in the products are formed than is used to break the bonds of the reactants. As
the gas burns, it gives off energy and raises the temperature of its surroundings.
Water has a high specific heat capacity and, therefore, demonstrates a relatively small change in
temperature for a given amount of heat absorbed. This capacity to absorb heat without
undergoing a large temperature change is why water is used to prevent burns during this
demonstration.
Methane is a colorless, odorless, highly flammable gas at room temperature and can be found in
a wide variety of sources on earth. On earth methane can be found as a major component of
natural gas that is stored in the earth's crust. Natural gas is combustible, and when burned it
gives off a great deal of energy. Unlike other fossil fuels, however, natural gas is clean burning
and emits lower levels of potentially harmful air pollutants.
*Real World Relevance:
Since we require energy constantly, to heat our homes, cook our food, and generate our
electricity, natural gas has been elevated to a high level of importance in our society, and in our
lives. Even though natural gas emits fewer air pollutants, the combustion of this fossil fuel still
releases large amounts of carbon dioxide (CO2) into the atmosphere. Carbon dioxide is a
greenhouse gas and it is hypothesized that the increased levels of greenhouse gases from human
generated emissions are contributing to global climate change. Increased levels of CO2 enhance
the atmosphere’s ability to trap heat from the sun and prevent it from radiating back out into
space.
Questions:
1. Describe the combustion process that is occurring during this reaction. What can you see,
hear, feel, or smell?
 See the flames/light; hear it burning; feel the heat; potentially smell natural gas
2. Is this reaction endothermic or exothermic? How can you tell?
 Exothermic – heat is being released to the surroundings
3. What is stopping our hands from getting burnt during this reaction?
 Water – a high specific heat capacity allows water to absorb heath without
undergoing a large temperature change
4. During this combustion reaction, methane and oxygen are the reactants. Can you predict
what the products will be?
 Carbon dioxide (CO2) and water (2H2O)
5. If natural gas is a good source of methane, why might this combustion reaction be
important in everyday life?
 Natural gas is used to heat our homes, cook food, and generate electricity
6. Do either of the products from this combustion reaction cause a global concern?
 Carbon dioxide is a greenhouse gas and it is hypothesized that the increased levels
of greenhouse gases from human generated emissions are contributing to global
climate change.
Additional Notes:
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There are a couple of modifications that can be made to this demonstration:
o ‘Methane Mamba’ bubbles the methane gas through an inverted 1 liter bottle that
is cut in half. This allows the bubbles to spill out of the top in a snake like fashion.
o By attaching a glass funnel to the rubber hose and dipping it in soapy water,
individual bubbles can be created. When released from the funnel, the bubble will
float toward the ceiling. Using an extended ignition device, the combustion
reaction can occur in mid-air.
This demonstration should only be used once students have demonstrated the ability to
follow proper safety precautions.
I would recommend practicing the procedure on your own before attempting it with high
school students.
References:
Draper, D & Reed, M.G. (2009). Our Environment: A Canadian perspective (4th ed.). USA:
Nelson Education Ltd.
Education Portal
http://education-portal.com/academy/lesson/what-is-methane-reactions-formulaquiz.html#lesson
Elmhurst College Virtual Chemistry Book
http://www.elmhurst.edu/~chm/vchembook/510naturalgas.html
Methane Bubbles Combustion Reaction
https://www.youtube.com/watch?v=LzagxjtZrJY
Methane Mamba
http://chemmovies.unl.edu/chemistry/beckerdemos/BD015.html
Middle School Chemistry
http://www.middleschoolchemistry.com/multimedia/chapter6/lesson7
Natural Gas Bubble Bath
http://www.digitaldapp.org/demos/documents/naturalgasbubblebath.pdf
Tro, N.J. (2011). Chemistry: A molecular approach (2nd ed.). New Jersey, USA: Pearson
Education Inc.
Combustion of Methane
Observations & Discussion Questions
1. Describe the combustion process that is occurring during this reaction. What can you see,
hear, feel, or smell?
2. Is this reaction endothermic or exothermic? How can you tell?
3. What is stopping our hands from getting burnt during this reaction?
4. During this combustion reaction, methane and oxygen are the reactants. Can you predict
what the products will be?
5. If natural gas is a good source of methane, why might this combustion reaction be
important in everyday life?
6. Do any of the products from this combustion reaction cause a global concern?