Clint Heikkila Wood-to-Wheels Lesson 4
Comparing the By Products of Combustion of a Biofuel and a Fossil Fuel
Which fuel- ethanol or kerosene- will release the most particulates and carbon dioxide?
(Which is the cleaner burning fuel?)
Class: Chemistry / 11th Grade
Time: One Class Periods (50 minutes)
Location: Chemistry Lab
Learning Objectives- SWBAT:
Set up and conduct an experiment in which a fossil fuel (kerosene) and a biofuel (ethanol) are
combusted and measure the byproducts (particulate matter and carbon dioxide) of each reaction
for comparison.
Michigan Content Standards:
C1.1C Conduct scientific investigations using appropriate tools and techniques (e.g., selecting an
Instrument that measures the desired quantity–length, volume, weight, time interval).
C1.1E Describe a reason for a given conclusion using evidence from an investigation.
C5.2A Balance simple chemical equations applying the conservation of matter.
C1.1C Conduct scientific investigations using appropriate tools and techniques (e.g., selecting an
Instrument that measures the desired quantity–length, volume, weight, time interval).
C5.7C Describe tests that can be used to distinguish an acid from a base.
Overview: In this lesson, the students will combust a sample of ethanol and a sample of kerosene in a
glass, wick-type fuel burner. They then first make a comparative measurement of the amount of
particulate matter (soot) given off by each fire. Secondly, they measure the comparative amount of
carbon dioxide produced by each combustion reaction. The first experiment uses a qualitative
measurement based on how “black” a collection material becomes after being exposed to the exhaust
stream. The second involves capturing a sample of each exhaust gas, dissolving the collected gases in
water that is loaded with an indicator dye, and using an acid-base titration to determine the relative
amount of carbon dioxide in each of the solutions made from the exhaust gases.
This activity is also one of three in the lab kit called “Biofuels- Investigating Ethanol
Production and Combustion” (the same kit used in Lesson 2 of this unit). Ordering information for this
kit is as follows:
Supplier:
Lab Kit Title:
Product Number:
Link:
Enasco
Biofuels: Investigating Ethanol Production and Combustion Lab
C29169M
http://www.enasco.com/product/C29169M
Lesson Core
The Guiding Question:
How does the amount of particulate matter and carbon dioxide produced by burning ethanol compare
to the amount of particulate matter and carbon dioxide produced by burning kerosene?
●
Materials and Equipment Needed (per lab station):
(1) Lab kit- “Biofuels- Investigating Ethanol Production and Combustion”
*following is a list of needed materials that are not included in the kit
(1) pair of tongs
access to water
●
Safety precautions: Review lab safety guidelines as pertaining to open flames (hair and loose
clothing tied back, know location of fire extinguisher, etc). Students should wear safety glasses
and be experts in the safe handling of flammable materials. Ensure that there is adequate
ventilation in the room to prevent the accumulation up of smoke and fumes. Students also need
to be instructed in the safe handling of sodium hydroxide, a strong base which can cause
damage to skin and clothing.
●
Advanced Preparation: The students should be able to set up all equipment used in this
lesson as well as measure out all needed amounts of materials. The teacher should ensure that
all of the fuel burners have fuel in them and are in good working order prior to this activity.
●
Engage: Prior to beginning the lab activity, ask the class to review how we “get our hands on”
the energy we use to power cars. They should be able to track through the steps of converting
the chemical potential energy stored in fuels to heat energy by burning the fuel, and converting
the heat energy released in combustion to mechanical energy in an engine. This lab activity
will focus on analyzing the chemical reaction of fuel combustion, specifically the products
created and released in these reactions. Using the concept of conservation of mass, discuss
how everything that goes in to a fire comes out of the fire. We cannot burn something and
simply have everything “go away”. Write the skeletal chemical equations for each combustion
reaction on the white board and have the students balance them. Be sure to point out that these
equations represent the complete combustion of both fuels, but in real life we rarely get this
when we burn a fuel. Since we do not use pure oxygen as a reactant, but rather introduce the
oxygen by adding air to the engine, we often get incomplete combustion. Thus, not all of the
carbon in the fuel gets converted into carbon dioxide and some of it is emitted as “plain”
carbon, or soot. This soot is known as particulate matter and is one of the major pollutants
found in our atmosphere. Finally, tell them that in this experiment they will be measuring and
comparing the amount of pollution each fuel emits in the form of particulates and the
greenhouse gas carbon dioxide.
C2H5OH + 3O2 --------->
ethanol
2C12H26
ethanol
2CO2
+ 37O2 ---------> 24CO2
+ 3H2O
+ 26H2O
+ energy
+ energy
Before going into the lab, the students are asked to predict any differences they will find in the
amounts of particulate matter and carbon dioxide released from the combustion of each fuel.
●
Explore: Working in lab groups, the students will then set up the fuel burners and conduct the
two investigations. Each fuel is burned three times for a total of six trials. A detailed
procedure for this activity is included with the Lab Kit (copyright restrictions prevent the
procedure from being detailed here), including instructions for the acid-base titration used in
measuring carbon dioxide levels. By the end of the lab procedure, each group should have all
measurements needed to compare the products of each combustion reaction.
Explain and Elaboration: This will be done in the lab reports they are to create for all three
lab investigations. Remind the students to save all notes and handouts from this activity as well
as all data recorded in the tests. Students should account for the following in their summaries
for this activity:
-Which fuel released more particulates over equal time periods of being burned?
-Which fuel released more carbon dioxide over equal time periods of being burned?
-Identify potential sources of error that may have affected your results (how comfortable are
you with your results?)
-What would you do differently if you were to perform this investigation again?
-Kerosene is very similar to gasoline- what other information would you like to know before
deciding what fuel is better for the environment? How could you collect this information?
●
Evaluate and Lesson Closure:
If time permits, each group could share their results with the rest of the class. Follow this by
asking the questions below to check for understanding of the titration procedure. Remind the
students to save all notes and handouts from this activity (including all measured data) as it will
be part of a lab report they are to create at the end of the unit.
-What were your controls in this experiment?
-What was the role of the indicator dye in this experiment?
-What did the color change tell you about what happened chemically in your solutions?
Also, if time allows, other problems associated with combustion could be discussed. While this
test focused on two pollutants all burning engines produce, there are others present in the
exhaust of real engines- including carbon monoxide, SOx gases, NOx gases, and unburned
hydrocarbon molecules. Again using the concept of conservation of mass, explain that if the
fuel is not pure we can get additional byproducts. For example, if there is any sulfur present in
the fuel, that sulfur will get reacted as well, producing sulfur-containing gases (SOx gases),
which can create acid rain in the atmosphere. Furthermore, since air is not pure oxygen, any
other gases (such as nitrogen) found in air are also going through the combustion reaction,
resulting in the production of nitrogen monoxide and nitrogen dioxide (commonly called NOx).
NOx gases are significant greenhouse gases and can additionally be converted into ozone in the
presence of sunlight. Ozone is a harmful substance when found close to Earth’s surface, being
destructive to materials and posing health problems to humans. Unburned hydrocarbon
molecules can also be converted into ozone in the atmosphere. The closer a real engine can get
to complete combustion, the cleaner its exhaust gases will be.
Lesson Extension
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Assessment Options: The class discussion at the end of the activity allows the teacher to
assess the overall understanding of how this procedure is used to compare amounts of
combustion byproducts and how acid-base titrations are performed. Individually, this will be
assessed with the lab report at the end of the unit. The following questions can be asked in the
class discussion to check for understanding of the procedure.
-What were your controls in this experiment?
-What was the role of the indicator dye in this experiment?
-What did the color change tell you about what happened chemically in your solutions?