In this lab, students will learn how chemistry is used in air bags. Students will model the inflation of an air bag by performing a series of reactions using baking soda and vinegar in a Ziploc bag. During this investigation, students will see that there is a relationship between the inflation size of the bag and the amount of reactants used. Finally, students will be challenged to design an air bag that can help an egg endure a crash test.
Elementary and Middle School
This lab will help prepare your students to meet the performance expectations in the following standards:
- 3-5-ETS1-1: Define a simple design problem reflecting a need or want that includes specified criteria for success and constraints on materials, time, or cost.
- 3-5-ETS1-3: Plan and carry out fair tests to which the variables are controlled and failure points are considered to identify aspects of a model or prototype that can be improved.
- Scientific and Engineering Practices:
- Using Mathematics and Computational Thinking
- Developing and Using Models
- Planning and Carrying Out Investigations
By the end of this lab, students should be able to:
- Understand that chemistry is used in real-life scenarios, like airbags.
- Understand the process by which airbags operate.
- Recognize that the amount of reactants used in a chemical reaction will affect the amount of product created.
- Identify a gas as a possible product of a chemical reaction.
This lab supports students’ understanding of:
- Chemical Change
Teacher Preparation: 20 minutes
Lesson: 2-3 hours
- Computer with internet access
- 25-mL graduated cylinder
- Weighing boats
- 150 mL of 5% vinegar solution (acetic acid)
- 10.5 g of baking soda (sodium bicarbonate)
- 1-quart Ziploc bag
- An egg in a plastic bag
- Two 1-quart Zip lock bags
- 5% vinegar solution (acetic acid)
- Baking soda (sodium bicarbonate)
- Graduated cylinder
- Always wear safety goggles when handling chemicals in the lab.
- Use caution when handling vinegar (acetic acid). If any acid comes into contact with skin, flush with water immediately.
- Always check for food allergies prior to beginning. In this case, ensure you have no egg allergies in your class.
- Students should wash their hands thoroughly before leaving the lab.
- When students complete the lab, instruct them how to clean up their materials and dispose of any chemicals.
- This lab was modified from the original version, Air Bag Stoichiometry for use specifically in the elementary or middle school classroom. It was developed as part of the AACT Strategic Plan and the work of the AACT Grade-Level Ambassadors.
- In the elementary classroom, teachers may want to consider watching the background videos (Part 1) as a class and answering the questions together.
- Part 2 may be done as a class demonstration depending on the amount of materials available and the level of the class. It might also be helpful to have the vinegar and baking soda pre-measured again depending on the availability of balances and the level of the class.
- In Part 2, the bag will inflate to about two-thirds of its capacity, 590 mL. The 1-quart bag is a volume of 946.6 mL, so the bag should not fully inflate. To inflate the bag fully to 940 mL, students would use 2.8 g of baking soda and 40 mL vinegar.
- For Part 3, it may be helpful to have a class discussion of what various vehicles might look like prior to beginning. This can be done as a class brainstorm or a teacher-led discussion depending on the level of the students. This is best done in groups.
- Below are a number of other AACT resources that use vinegar and baking soda to teach fundamental chemistry concepts for K-8 students:
For the Student
This investigation begins with an internet exploration of how car airbags work. Use the links below to answer the questions about air bags.
- How Stuff Works: How Airbags Work
- ACS Reactions: How Do Airbags Work?
- AumSum Kids How Do Airbags Work (0:00 - 1:05 of video)
- Why do cars have airbags?
- What makes an airbag inflate?
- What chemicals are used to inflate the airbag?
- What gas fills the air bag?
- How long does it take for the airbag to inflate?
You will create your own air bag technology using baking soda (sodium bicarbonate) and vinegar (acetic acid). When baking soda combines with vinegar, one of the products is carbon dioxide gas. This gas can be captured (in a bag) to be used for another purpose—like an air bag!
Today, we are going to attempt to find the right amounts of baking soda and vinegar needed to inflate the air bag. “The right amount” means your bag, a 1-quart zip lock, should fill up without popping open, and no baking soda or vinegar should be left in the bag.
Before starting, look over the data table. You will use specific amounts of vinegar and baking soda, and record a description of how the bag inflated, what chemical was left over, and how long it took for the reaction to take place each time.
Which bag do you predict will produce the greatest amount of CO2?
Circle your prediction:
- Bag 1: 25 mL of vinegar + 0.5 g of baking soda
- Bag 2: 25 mL of vinegar + 1.0 g of baking soda
- Bag 3: 25 mL of vinegar + 1.5 g of baking soda
- Bag 4: 25 mL of vinegar + 2.0 g of baking soda
- Bag 5: 25 mL of vinegar + 2.5 g of baking soda
- Bag 6: 25 mL of vinegar + 3.0 g of baking soda
- Always wear safety goggles when handling chemicals in the lab.
- Wash your hands thoroughly before leaving the lab.
- Follow the teacher’s instructions for cleanup of materials and disposal of chemicals.
- Weigh 0.5 grams of baking soda. Carefully pour it into a bag. Flatten the bag to remove any air.
- Add 25 mL of vinegar to the bag and seal the bag as quickly as possible. Start the timer. The bag should begin to inflate.
- When the bubbling stops, further mix the vinegar and baking soda by squishing and/or shaking the bag to make sure the reaction proceeds as far as possible. When no more bubbles are produced, stop the timer. Record how long it took for the chemicals to react.
- Test how inflated the bag is by pinching it. Write a description of the fullness of the bag in the data table. Also, make note if the bag feels warm or cold.
- Record in the data table whether there is any baking soda left in the bag.
- If all of the baking soda seems to be gone, open the bag and add a small amount of baking soda to see if any more bubbles form. If they do, then there is still some vinegar left in the bag. If not, then all of the vinegar reacted. Record in the data table.
- Repeat this process by doing 5 more reactions. Use the following amounts of baking soda for each of the reactions: 1.0g, 1.5 g, 2.0g, 2.5g, and 3.0 g.
|Bag#||Acetic acid (vinegar)||Sodium bicarbonate (Baking soda)||Observations of bag (fullness, warm/cold, other notes)||Leftover Baking Soda or Vinegar?||Time to fill the bag (seconds)|
|1||25 mL||0.5 g|
|2||25 mL||1.0 g|
|3||25 mL||1.5 g|
|4||25 mL||2.0 g|
|5||25 mL||2.5 g|
|6||25 mL||3.0 g|
- Did any bag fully inflate? If not, explain what you would do to fully inflate the bag.
- From your observations, predict how long it would take to fully inflate the bag.
- Did the bags get warmer or colder?
- Is this reaction a good candidate for the real car air bag? Why or why not?
Part 3: The Crash Test
Now you will conduct a crash test, keeping in mind your results from part 2. You will design and build a vehicle for your crash test dummy, which is a raw egg. The goal is to build a “vehicle” that will protect an egg from breaking when dropped from the given height.
The only materials you may use (choose from) are:
- 1 egg (inside a plastic bag)
- Two 1-quart zip lock bags
- 100 mL Vinegar (you don’t have to use all of it)
- Baking Soda
- Graduated Cylinder
Planning Your Work
As a group, complete the planning section below. Show your work to your teacher.
- How much baking soda and vinegar are you going to use? Remember, that the bag should inflate enough to protect the egg, but should not pop open!
- In the table below write a description/reasoning for the air bag you plan to create for the crash test, including the amounts of baking soda and vinegar. (You can choose to use either one or two bags in your vehicle design!)
|Acetic acid (vinegar)||Sodium bicarbonate (Baking soda)||Description/Reasoning for the air bag design|
- Your air bag is going to protect an egg as it is dropped from the given height. Describe the design of your vehicle as it is used to protect the egg. Draw a sketch of it in the space below.
- Show your completed planning section to your teacher.
- Once your planning section is approved, carry out the reaction and inflate the bag or bags according to your design.
- Show your bag or bags to your teacher for an examination.
- Assemble the inflated bag(s) and the egg (in a plastic bag) together as a “vehicle” based on your design from planning section above.
- When it’s your turn, drop your vehicle from the height determined by your teacher.
- Check your passenger (egg). Did it survive the crash? Show your vehicle to your teacher after the crash test.
- What was the condition of the passenger (egg) after the crash? Describe it.
- Did your passenger survive? If so, explain how your passenger survived. If your passenger did not survive, explain why it did not.
- How would you improve your design for a future crash test?