IIT/FIELD MUSEUM – High School Transformation Project
Lesson: Humpty Dumpty Meets the Air Bag
Glencoe Chemistry: Matter and Change
Unit 4 The Mole and Stoichiometry
Chapter 11 Stoichiometry
Section 11.1 Defining stoichiometry
Section 11.2 Stoichiometric calculations
Chapter 10 The Mole
Section 10.2 Mass and the mole
Section 10.3 Moles of compounds
Context of Lesson
Students should be developing their understanding of the concepts underlying
stoichiometry. These include: writing and balancing equations for chemical reactions; converting
given quantities of reactants and products among grams, liters, moles and other measurement
units; use of the coefficients of balanced equations as mole ratios to predict products made and
reactants required; and identifying limiting reactants, excess reactants and theoretical yield. They
should also understand that actual yield never equals theoretical yield. All of these topics are
covered in Chapter 10 of Glencoe Chemistry. This lab activity is best used after students have
learned about air bags located in the Teacher Background section of this lab. Use as Bell Ringer/Do
Now.
Students mix vinegar and baking soda (acetic acid and sodium hydrogen carbonate, also
known as sodium bicarbonate) in a closed “zip-lock” plastic sandwich bag to produce carbon
dioxide. The gas inflates the bag which is then fashioned to cushion an egg on its two meter fall.
Students are given a trial amount of reactants and then required to reason and calculate optimum
amounts of reactants to use for their “air bag.” This activity ends with an egg-drop contest.
The students should have experience doing stoichiometric calculations to solve various
problems. This activity is best used towards the end of the unit and readily provides formative or
summative assessment. After watching the students work, talking with them and grading their
reports, the teacher should be able to make curricular decisions (more stoichiometry practice vs.
beginning the next unit).
Main Goals/ Objectives:
The goals of the lesson are to encourage the students to think about a practical application
of stoichiometry (the air bag), experiment on their own using scientific process skills, practice
stoichiometry calculations and complete a lab report in the context of a fun, motivating activity. By
the end of this lesson, students will be able to:
 Solve practical stoichiometry problems on their own (or with a partner), including reasoning
and calculations involving stoichiometry.
 Using inquiry, design and create an air bag system, through experimentation, that will
cushion an egg from breaking when dropped from 2 meters.
 Write a report that describes their procedure and results.
Nature of Science: Integrated Theme
 Distinguish observations from inferences, explain that inferences should be based on
observations and the development of scientific knowledge involves both observations and
inferences so scientific knowledge is partially inferential.
 Explain that scientists’ background knowledge and creativity influence their doing inquiry so
they may have different observations and interpretations of the same phenomena.
 Explain how scientific theories are different from scientific laws: Scientific laws are more
likely observable patterns and scientific theories are explanations for observable patterns.
 Explain that scientists’ work is influenced by social and cultural environments.
 Explain that scientific knowledge should be based on empirical data.
Scientific Inquiry: Integrated Theme
 Explain that scientific investigations all begin with a question, but do not necessarily test a
hypothesis.
 Explain that inquiry procedures are guided by the question asked
 Explain that all scientists performing the same procedures may not get the same results.
 Explain that inquiry procedures can influence the results.
 Explain that research conclusions must be consistent with the data collected.
 Explain that scientific data are not the same as scientific evidence.
 Explain that explanations are developed from a combination of collected data and what is
already known.
General Alignment to Standards
STATE GOAL 11: Understand the processes of scientific inquiry and technological design to
investigate questions, conduct experiments and solve problems.
A. Know and apply the concepts, principles and processes of scientific inquiry.
 ILS 11.A.4a Formulate hypothesis referencing prior research and knowledge
 ILS 11.A.4b Conduct controlled experiments or simulations to test hypotheses
 ILS 11.A.4c Collect, organize and analyze data accurately and precisely
 ILS 11.A.4e Formulate alternative hypotheses to explain unexpected results
 ILS 11.A.5b Design procedures to test the selected hypothesis
 ILS 11.A.5c Conduct systematic controlled experiments to test the selected
hypotheses.
Materials
For each group of 2 students
 4 Sandwich sized zip-lock bags
 25 ml graduated cylinders
 100 mL acetic acid (vinegar)
 4 single pieces of toilet paper
 20 g Baking soda
 1 or 2 Raw or boiled eggs
 If directed by their teacher, students may bring other materials from home
 Cardboard box for egg drop contest (~27cm X 18cm X 13cm (~10.5in X 7in X 5in) work well)
Class Materials
 Class set of safety goggles
 Electronic balances
 Meter sticks
 Ring stand with clamp to hold meter stick 2 meters above the ground for the contest
 Masking tape
 Sinks with running water
 Newspaper for the floor where egg drop will be done. (Tape down the newspaper. If
carpeted, use a large plastic sheet, such as a large garbage bag that has been cut open, and
place it under the newspaper. Another option is to drop the egg vehicles into a large box.)
Safety
 A few students may be allergic to vinegar. Check for this issue ahead of time and prepare for
instances of allergic reactions that are unknown to the student.
 Eye protection should be worn throughout this activity.
 Because vinegar is a household product, students will underestimate safety concerns.
 When working with the vinegar (acetic acid), use great care as it can damage eyes, skin,
rugs, clothing, and shoes.
 Spilled vinegar should be neutralized by being sprinkled with baking soda before being
cleaned up and placed in the garbage. Rinse the area with water and wipe dry before
continuing .
 A reaction product is a gas (CO2), so pressure situations causing minor explosions may occur.
Teacher Background
HOW IT WORKS Air Bags
Purpose
Students will learn how stoichiometry is critically important in the functioning of air bags.
Background
 The first proposal to equip automobiles with air bags was made in the early 1950s, but it
was not until the late 1980s that reliable and safe air bags were offered to the public as an
option.
 Full deployment of an air bag takes about 40 milliseconds. The bag’s velocity as it deploys is
approximately 200 mph (322 kph).
 Air bags begin to deflate by the time they make contact with a person. This helps to provide
a cushioning effect by allowing a controlled deceleration of the person’s body rather than
an abrupt stop. The deflation is controlled by carefully designed vents in the bag.
 The mechanism used for the air bag on the passenger side is shaped differently from the
one used on the driver side, but the chemistry is the same.
Visual Learning
Refer students to the illustration of the inflating bag. Ask under what circumstances the air bag
could be a danger to the driver. (See attachment)
Teaching Strategies
 Have students research statistics on the number of lives saved by air bags.
 Ask students to comment on the stability of sodium azide at high temperatures.
 Have students recall the properties of alkali metals. Ask why the air bag design includes the
reaction of sodium and potassium with sand.
The Lesson
Day One
Bell Ringer
Direct students to read about air bags from Teacher Background.
Ask students if they or anyone they know has ever been involved in an accident where air bags
went off. Ask guiding questions to engage students in the lesson.
 What happened?
 Were you or someone else hurt?
 Did the air bags protect you? etc.
Discuss responses for about 5 minutes.
Class activity
Hand out the lab sheet. Call on a student to read aloud the poem and introductory paragraph on
the lab sheet.
Ask the students what questions they have. Once all questions are answered direct the students to
complete Step 1 with their teammates. Have them call you over to check their work.
If correct, have them read Steps 2 while you work with other students. If incorrect, give them a
guiding question such as “How can you fix having 7 carbons on the reactant side and 9 carbons on
the product side?” or “Which element is not balanced?”
Once students have read Step 2, ask if there are any questions. Answer any questions and then
direct students to carry out Step 2. Direct them to move on to Step 3 when they have finished Step
2. Check on each team regularly to ensure adequate progress and understanding. (The volume
determination could be done as a class discussion or demonstration if time is a factor). (Ex. Blow up
the bag like a balloon, fill with water and measure volume with graduated cylinder, or estimate the
volume using measurements of length x width x height. Answers will vary).
Check each team’s answer to Step 3 and then have them move on to Step 4 and Step 5.
Once teams have designed their vehicles for eggs, allow them to begin the building process.
Homework
Complete Step 5 if necessary.
Work on building their vehicle.
Be prepared to finish building vehicle within the first 10 minutes of class tomorrow.
Day Two:
Bell Ringer
Tell students to begin finishing up their vehicles. Allow 10 minutes and then begin the contest.
While students work, set up a ring stand with clamp, then clamp the meter stick so its top is 2
meters from the floor. Tape newspaper (with plastic underneath if carpeted) to the floor in the area
where the egg dropping will occur. Once the drop area is ready, announce that all vehicles need to
be assembled and brought to the egg drop area.
Activity
Discuss the need for consistency in an investigation. Pick one student to drop each vehicle to keep
the actual drop consistent. Each team should get the mass of their vehicle by having another
student weigh the vehicle just before it is dropped. Record the mass of each vehicle and the egg
survival for each group.
Direct a class discussion on the project, results, conclusions, inquiry and nature of science.
Suggested questions include:
 In what ways did the question asked influence our decisions, actions and designs?
 Why were there so many different designs for the airbags and vehicles?
 Not everyone has the same ideas for solving a problem such as designing an air bag. Why?
 In life, there are all sorts of problems and questions we could ask. Which ones do we decide
are priorities if money and person power are limited? Should all cars have air bags? How
many?
 Where should they be in a car?
 What was the initial problem to solve? Did we have a hypothesis? Did we have a
hypothesis?
 Why didn’t each team get the same results for Step 2 when they all did the same
procedure?
 How did we decide if the calculated values from step 4 were most efficient for inflating the
airbag?
 What did we use as evidence to determine the success of the airbag in the vehicle?
 How did we know which airbags were effective? Efficient?
Homework
Students need to finish their lab reports. You could make this assignment an individual report or a
lab team report.
Students should include the following in their lab report:
 Title of lab
 Name(s) of individual or team members
 General experimental procedure used by individual or research team, with notes and
observations of your work and testing
 Written and balanced equation for the reaction




Calculations for the amounts of reactants you used and the amounts of products you
expected for Humpty’s ride
A sketch (or photo) of your “vehicle” (if possible reserve the school digital camera and have
a student photograph each egg-drop before and during, or if possible use your own)
Results of your crash test with comments on your design and implementation and notes of
changes you would make to further protect Humpty.
The mass of your protection system, with egg and whether your egg survived or not.
Assessment:
 As students work, walk around the room and talk to them in their lab groups to help as
needed and to check their understanding of stoichiometry calculations. Have they had
enough practice to do these on their own? Will they need to do more practice problems?
(Possible practice resources are the Solving Problems: A Chemistry Handbook; Chapter
11 in the Chapters 9 -12 Resources Book; Science Notebook; Chapter 11 in the Chemistry
Challenge Problems Lab Manual; and/or Solutions Manual)).
 Student responses during class discussions.
 The lab report should be assessed based on completion of each requirement and
calculations should be checked for completion and accuracy.
 The summative assessment for the stoichiometry unit could include an air bag calculation or
essay.
 Success of airbag for egg.
 Mass of vehicle, lowest mass with success of airbag and survival of egg is best.
Modifications/Accommodations
 If two days are not available, this whole activity could be done as a teacher directed, class
demonstration/discussion. Much of the inquiry would be lost, as well as some of the
motivation.
 If students struggle with the calculations, these can be done with teacher direction and/or
step by step work with the class.
 The lab report requirements can be shortened or eliminated.
 A related reading with questions to answer could be developed as another assessment
strategy.
 For students with an allergy to vinegar, provide them with a team’s data so they can
complete the calculations and questions. An alternative assignment could be developed
using the information in the enrichment section.
 There is some controversy over the use of air bags in automobiles. Ask the students why
they think this might be and ask each to find reference to this effect on the internet.
 More stoichiometry problems could be done for practice using the equations for operation
of air bags from the Chemistry behind air bags website.
 The Gas Laws could be linked to calculations of inflation of air bags.
 Print photos of the students “vehicles”. Display for parents and other classes to see. A
student could be recruited to do this.
Enrichment
For more information see the following:
http://www.howstuffworks.com/airbag.htm
Chemistry behind airbags:
http://www.chemistry.wustl.edu/~edudev/LabTutorials/Airbags/airbags.html
General info on airbags http://en.wikipedia.org/wiki/Airbag
Facts about airbags http://www.nsc.org/partners/facts1.htm#A
Attachments:
Handout of the lab activity
The idea for this lab came from: “It’s a Crash Test, Dummy” retrieved from
http://www.sciencenetlinks.com/lessons.cfm?BenchmarkID=3&DocID=147 2/15/07
Fun with Stoichiometry: Humpty Dumpty Meets the Air Bag!
Step 1:
Humpty Dumpty sat on a wall,
Humpty Dumpty had a great fall;
All the King's horses, and all the King's men
Could not put Humpty Dumpty together again.
What if Humpty had an airbag? Design one for him and we’ll have an
egg drop contest! Your objective will be to create an airbag that will
allow Humpty Dumpty to survive the fall. In this activity you and your
team will design and test your own airbag system by combining baking
soda (sodium hydrogen carbonate, also known as sodium bicarbonate,
NaHCO3) and vinegar (acetic acid, CH3COOH) in re-closeable sandwich
bags. Carbon dioxide (CO2), water (H2O), and sodium acetate
(NaCH3COO) are the products of this reaction. Which product do you
think will be the gas that will inflate Humpty’s airbag?
Write the chemical equation for the reaction described above and then balance the equation.
NaHCO3 + CH3COOH
Step 2:
A. You will test out the reaction by adding 1 gram of NaHCO3 to 25 ml of vinegar in a re-closeable
sandwich bag.
1. Wrap the sodium bicarbonate, NaHCO3, in a tissue before dropping it into the vinegar.
This will allow you to control the reaction a bit.
2. Determine the best way to drop the wrapped NaHCO3 into the vinegar in the bag without
losing any gas. You will need to flatten the bag to remove air and seal the bag as quickly as
possible.
3. Drop the NaHCO3 into the vinegar and record your observations.
4. After the reaction becomes slow or stops, mix the ingredients to make sure the reaction is
complete.
5. Record your observations.
B. Pay special attention to the inflation of the bag and think about how you could change this to
make a better airbag.
Step 3:
A. Based on the first investigation, calculate the amounts of vinegar and baking soda you would
need to react to fully inflate the bag and leave the least amount of left over reactants. In other
words, what is the most CO2 you can generate to fill the bag, but not have it pop open and not
leave reactants? The following information will be useful:
1. You will need to get the volume of the bag. Create your own plan to do this. Describe it in
the space below and record you measurements and volume.
2. The molar mass of NaHCO3 is 84 g/mole
3. Vinegar is a 1M solution of acetic acid (CH3COOH) in water. That means there is one mole of
acetic acid in 1 liter of vinegar. The rest of the solution is water. If you use 25 ml, (0.025
liters) of vinegar, how many moles of acetic acid are you using?
Step 4:
Using your calculated values of NaHCO3 and vinegar, test your hypotheses by experimentation to
determine the best amounts of vinegar and baking soda to use in your airbag. Record all ideas,
procedures, calculations and investigations results in the space below. You will need to turn all of
this in with your lab report.
Step 5:
Once you determine how to make the most efficient air bag (efficient means using the least mass of
chemicals to create the maximum carbon dioxide gas), design and build a vehicle for Humpty
Dumpty (a raw egg) so that when he falls, the airbag will protect him. Humpty will be dropped from
a height of 2 meters and he is depending on your design for survival.
The only materials you can use for the vehicle are:
 small cardboard box
 two ziplock plastic bags
 1M solution of acetic acid (vinegar)
 Sodium hydrogen carbonate ( sodium bicarbonate), NaHCO3 (baking soda)
 tape
During the development of your vehicle, you may also use:
 graduated cylinders and other glassware in the classroom
 electronic balance
 meter stick
Note: You will not be given an egg for testing your design; eggs will only be used in the final
competition.
Thinking Critically:
1. Students should predict that the sand SiO2 is the least important and that it does not need to
be present in a precise stoichiometric ratio. It has no effect on the quantity of nitrogen gas
generated, so the air bag would inflate correctly without it. The purpose for its inclusion is
to convert harmful reaction byproducts (Na2O and K2O) to a more harmless form (glass).
2. Students should find that the ratio is 5 mole NaN3 to 1 mole KNO3.
10Na(s) + 2KNO3(s)
5Na2O(s) + K2O(s) + N2(g). They should correctly conclude that an
excess of KNO3 would not be detrimental to the operation of the air bag. Any excess would
not react because there would be nothing for it to react with.