Introduction
If you are not already a driver, you are likely learning to drive, or have at least thought about starting this process soon. If anything, you know that all standard vehicles these days have airbags which are there to protect the driver and potential passengers in the event of a car accident. You also know that an airbag is basically a large bag which fills with gas very quickly to prevent the occupants of the vehicle from slamming their head against the steering wheel, as well as the side windows (in most modern vehicles). So, what don’t you know about airbags? Plenty! This activity will help you use your chemistry skills to not only understand the true workings of how an airbag deploys, but to analyze specific chemical amounts needed, in specific conditions, as well as to evaluate several safety precautions and potential improvements which can be made to airbags.
Task
You will be challenged to develop the ideal airbag (it can be real or hypothetical). Once you have analyzed how an airbag works and evaluated a set of conditions using one of the most common airbag reactions, you will be tasked with looking into alterative reactions and potential improvements. If you feel there is one ultimate method out there which is the ideal airbag reaction, then you will create a persuasive argument as to why this is the best method out there. If you feel nothing is currently ideal, you will create a hypothetical substance/method and describe its perfect properties and why it would be the most ideal.
Process
Part 1: How Do Airbags Protect Drivers?
In this step, you will conduct research on airbags to learn how they work, and how they protect drivers. In addition, you will learn about the most common chemical reaction used in airbags. You can use the following links to get a jump start on your research, but feel free to find resources of your own as well!
- https://www.scientificamerican.com/article/how-do-air-bags-work/
- https://www.mcgill.ca/oss/article/technology/fascinating-chemistry-airbags
- https://blogs.ubc.ca/communicatingchemistry2017w110/2017/11/20/how-do-air-bags-work/
- https://www.autobytel.com/car-ownership/technology/how-do-airbags-work-127047/
A:
Conduct research on airbags and take notes on your findings, including citing the resources you used (please use APA formatting for citations). Write one to two paragraphs which describe how airbags work in automobiles, and how this results in protecting the driver and other passengers. Include “works cited” below your paragraph(s).
B:
A common reaction used for the deployment of airbags is the decomposition of sodium azide (NaN₃). An electrical signal causes this chemical to break down, producing elemental sodium and nitrogen gas. Write the balanced chemical equation for this reaction.
C:
Now run this phet simulation that demonstrates gas properties. Select “Ideal” from the simulation choices. The simulation shows a container with a lid on top. The lid can be opened and closed by dragging it left and right. On the left side of the container is a handle. Drag this handle right or left to decrease or increase the volume of the container. On the top right of the container are a thermometer and a pressure gauge. Follow these steps to investigate the simulation and complete the follow-up questions.
Simulation Procedure:
- Reduce the container to its smallest possible volume by dragging the handle as far right as possible.
- In the menu to the right, click the green “+” sign next to “Particles” and add 75 particles of “heavy species” to the container.
- In the menu, under “Hold Constant”, select pressure (V). Pressure will not be allowed to change.
- Increase, one particle at a time, the number of heavy species to 210.
What do you observe as the number of particles are increased from 75 to 210 at constant pressure?
D:
Go back to the simulation and increase the number of particles of heavy species to 250. What change do you observe?
E:
Based on your observations, relate the container from the simulation to a vehicle airbag. What do you think would happen to an inflatable airbag if gas molecules were to be continuously added to it, like the container in the simulation?
Part 2: Analyzing the Reaction in an Airbag Inflator
Here, you are tasked with designing a driver’s front airbag for a specific car model so it will protect the driver as effectively as possible. The reaction in this airbag will be the most common: decomposition of sodium azide.
A:
For this car, the ideal airbag conditions must inflate to a volume of 62 liters, and a pressure of 1.25 atmospheres to provide an adequate cushion for the driver’s head. One of the main components of an airbag is the gas that fills it. As part of the design process, you need to determine the exact amount of nitrogen that should be produced. Assume that the nitrogen produced by the chemical reaction is at a temperature of 492℃ and that the nitrogen gas behaves like an ideal gas. Calculate the number of moles of nitrogen required to fill the airbag and SHOW YOUR WORK. (This can be handwritten and attached here via “insert image file”. Otherwise, you can type out the calculation work).
B:
Recall the balanced chemical equation from question B part 1:
Re-write it here ______________________________________________________
Calculate the mass of sodium azide needed to decompose and produce the number of moles of nitrogen which you calculated in question A of this task. (Again, ensure to show your work as you did in part A!)
C:
Describe what would happen if the amount of sodium azide used was much more than what you calculated for these conditions.
D:
Describe what would happen if the amount of sodium azide used was much less than what you calculated for these conditions.
E:
Do you think a strong understanding of chemistry is important for someone charged with designing airbags? Explain your reasoning!
Part 3: The Ricks of Propellants in Airbag Inflators, and Potential Solutions
Sodium azide is just one of the many propellants that can be used to produce nitrogen to inflate an airbag. Many modern airbags use other chemicals instead. The choice of propellant depends on many factors. In this task, you will discover why sodium azide may not be an ideal choice for air bag propellants, and you will be charged will looking into alternative methods.
A:
Read this article to gain a clear understanding of criteria and constraints as they pertain to an engineering design. Now, imagine you are an engineer developing airbags for vehicles. What criteria and constraints do you anticipate you would need to consider? List at least three criteria, and three constraints for this endeavor.
B:
Sodium azide is stable at room temperature but decomposes quickly at temperatures above 300℃. It is moderately inexpensive to manufacture but is highly toxic. Read this fact sheet on the potential dangers of sodium azide. Based on this information, does sodium azide seem like a good match for the criteria and constraints you listed in question A? In what ways is sodium azide a good choice for an airbag design, and in what ways is it not?
C:
Read this last article and conduct any additional research you need. In looking for a chemical to replace sodium azide in airbags, suppose that a cheap, nontoxic, and environmentally friendly chemical was found that decomposed more slowly, producing nitrogen over a period of several seconds. Would this chemical be a good replacement for sodium azide in airbags? Why or why not.
Part 4: Summary Assignment: The Ideal Airbag
With your group members, develop an oral, written, or multi-media presentation which supports your ideal method for deployment of an airbag. This can be a method which is already in use, or it can be a hypothetical method or substance (chemical make-up would not be required, only properties!). Ensure that your choice meets all criteria, and almost no constraints as you described previously! Use the research gained in this activity to support your ideas.
Evaluation
|
Part 1: How do Airbags Protect Drivers? A: Explain what causes airbags to inflate when a car accident occurs. B: Write the correct balanced chemical equation for the decomposition rxn described. C: Describe the effect of adding gas to enclosed container at constant pressure. D: Describe the effect of adding even more gas to the same closed container. E: Relate the simulation findings to the behavior of an enclosed airbag as gas is added.
|
Total Points:28 A: 10 B: 5 C: 4 D: 4 E: 5
|
Criteria for points: A: Students give a clear, step-by-step explanation, and properly site sources. B: Chemical formulas are written correctly for reactants and products and equation is balanced. C: Students appear to have followed the procedure correctly, and describe the effect of gas added accurately. D: Students describe the effect of additional gas added accurately. E: Students accurately use the simulation findings to clearly describe how it would relate in an airbag. |
|---|---|---|
|
Part 2: Analyzing the Reaction in an Airbag Inflator A: Determine the amount of nitrogen gas that should be produced for the proposed airbag. B: Calculate the mass of sodium azide needed. C: Describe the result of using too much sodium azide. D: Describe the result of using too little sodium azide. E: Support reasoning behind an opinion. |
Total Points: 32 A: 10 B: 10 C: 4 D: 4 E: 4 |
Criteria for Points: A: Student work is shown and calculated accurately, with correct equation, units, and conversions made. B: Student work is shown with correct stoichiometry. C: Results are described clearly and accurately in complete sentences. D: Results are described clearly and accurately in complete sentences. E: An opinion is formulated and supported by clear reasoning. |
|
Part 3: The Risks of Propellants in Airbag Inflators, and Potential Solutions A: List criteria and constraints that should be considered when designing an airbag. B: Evaluate sodium azide using the criteria and constraints developed. C: Evaluate a given hypothetical substance using the criteria and constraints developed. |
Total Points: 15 A: 5 B: 5 C: 5 |
Criteria for Points: A: Criteria and constraints listed are valid and important to the engineering of a real airbag. At least 3 for each are given. B: There are both good and bad aspects of sodium azide discussed. C: The hypothetical substance is called either a good or bad choice with clear reasoning to support choice. |
|
Part 4: Summary Assignment: The Ideal Airbag A: Presentation B: Collaboration C: Criteria met, constraints addressed. D: Research was used. |
Total Points: 25 A: 10 B: 5 C: 5 D: 5 |
Criteria for Points: A: The group presents their ideal airbag orally, in a written format, or as a multimedia presentation in a clear and well organized fashion. B: Aspects of collaboration were seen throughout the WebQuest, as well as defined visibly in all Parts. C: The criteria and constraints defined in Part 3 are considered for the ideal airbag presented. D: Research is clearly seen with proper references and citations listed. |
Conclusion
In the end, airbags are necessary to save lives. I am hopeful that through this experience you were able to see the important role chemistry has in the engineering and evaluation of safe airbags. Also, that filling the shoes of the engineer is a lofty feat, taking many measures to reach the end goal. Please work with your group members to answer the following reflection questions:
1. Did you use your understanding of ideal gases and gas stoichiometry to correctly calculate the amount of sodium azide needed for the proposed set of conditions?
2. If it were a real airbag, going into a real car, how could mis-calculations, improper units, or incorrect equations result in disaster?
3. You looked into several chemicals and methods used for the deployment of an airbag. Do you feel safe in your own vehicles knowing more about the potential risks of these substances? Why or why not?
4. Did you feel the simulation was helpful in understanding how an airbag fills with gas? Explain if necessary.
5. Were the articles and resources provided useful in answering the WebQuest questions? Did you end up using any additional resources for any piece of this WebQuest?
Credits
Print Resources:
Your periodic table
Your notes on gas laws
Technology needed:
Your laptop
A scientific calculator
Internet Resources:
Centers for Disease Control and Prevention (CDC), 2018. US Department of Health and Human Services. “Facts About Sodium Azide”. Retrieved on June 15, 2023 from https://emergency.cdc.gov/agent/sodiumazide/basics/facts.asp#:~:text=Breathing%20the%20gas%20that%20is,making%20it%20less%20harmful%20outdoors.
Dunn, B. 2023. AutoWeb. Retrieved on June 15, 2023 from https://www.autobytel.com/car-ownership/technology/how-do-airbags-work-127047/.
Edmentum. Retrieved on June 15, 2023 from https://www.edmentum.com/.
Halford, B. 2018. Chemical and Engineering News: ACS. “What chemicals make airbags inflate, and how have they changed over time?”. Retrieved on June 15, 2023 from https://cen.acs.org/safety/chemicals-make-airbags-inflate-changed/100/i41.
Holt, Weinert, & Winston. “Chemistry in Action: Airbags and Stoichiometry”. Retrieved on June 15, 2023 from https://web1.tvusd.k12.ca.us/gohs/myoung/Chem.%2016-17/Airbag%20Lab%20Reading%20and%20Questions.pdf.
Merola, J. S. 1999. Scientific American. “How do airbags work?”. Retrieved on June 15, 2023 from https://www.scientificamerican.com/article/how-do-air-bags-work/.
NAEP Technology and Engineering Literacy Project Committees and Staff, 2020. National Assessment Governing Board. Retrieved on June 15, 2023 from https://www.nagb.gov/naep-subject-areas/technology-and-engineering-literacy/framework-archive/2014-technology-framework/toc/ch_2/design/design2.html#:~:text=Types%20of%20criteria%20and%20constraints,%2C%20aesthetic%20considerations%2C%20and%20policies.
PhET Interactive Simulations. University of Colorado. Retrieved on June 15, 2023 from https://phet.colorado.edu/sims/html/gas-properties/latest/gas-properties_all.html.
Schwarcz, J. PHD. 2019. McGill University: Office for Science and Society. “The fascinating chemistry of airbags”. Retrieved on June 15, 2023 from https://www.mcgill.ca/oss/article/technology/fascinating-chemistry-airbags.
Wang, X. 2017. Communicating Chemistry: WordPress. “How do airbags work? Deadly poison in your car’s airbag!”. Retrieved on June 15, 2023 from https://blogs.ubc.ca/communicatingchemistry2017w110/2017/11/20/how-do-air-bags-work/.