1. Airbags- Not just hot air
Catherine Waller
Harpers Ferry Middle School
Abstract
Project Description
Assessment of Project
Teams were provided:
A pretest of engineering design vocabulary terms.
An airbag study guide for the web quest.
A data table for recording the testing combinations for the desired airbags, and a description for a pinch test to record how much the bag inflated.
A procedure page for designing the vehicle with the constraints including an analysis and conclusions section to be completed after all testing was complete.
A posttest of engineering design vocabulary terms.
The final design project was to construct a simple vehicle with airbags filled to at least 90% with carbon dioxide gas that will protect a passenger (1 uncooked egg) from a drop of 2 meters. The challenge was to test combinations of sodium bicarbonate and acetic acid until an optimum result was found. First students used 25 ml of acidic acid and gradually increased the sodium bicarbonate. Then they changed the acid to 30 ml and continued to test. Results showed the bags inflated better with 30 ml. Inflation of the bags was measured by using a pinch test. Students shared data and chose a specific combination for their design. They designed a simple vehicle using limited materials and inserted their passenger (egg). They tested by dropping from a height of 2 meters. Results were evaluated. They completed a redesign and retested with overall better results.
Complete a web quest to research how airbags work. Work in groups of two, read articles and answer assigned questions. Review findings as a class. Work with partner to create airbags using a mixture of sodium bicarbonate (baking soda) and acetic acid (vinegar). Find the ideal combination of these two substances by producing 90% of carbon dioxide gas to fill a sandwich bag without the bag popping open. Complete a data table to record results. Once the desired result is reached, design a “vehicle” for a crash test using a raw egg as the passenger and limited materials. The goal is to design the vehicle and use the air bags to protect the egg from breaking when dropped from a height of two meters.
Constraints for final design per group:
Required- choose 1 from the provided vehicles- various sizes of tissue boxes, pop tart boxes, butter tubs; 2 sandwich bags; 1 meter stick.
Optional- 2 pieces of construction paper or notebook paper, 2 tissues or 2 plastic gelatin shot cups, 12 inches of scotch tape.
Engineering Design Products
Collecting data
WV NxGen Standards purpose
S.6-8.ETS.2 Evaluate competing design solutions using a systematic process to determine how well they meet the criteria and constraints of the problem.
Finding desired gas result
Evaluate/Reflect
This was a fun and engaging project. It took us longer than I had expected. I had originally planned on a week, but it took us two to complete. Several of my students had not used a triple beam balance prior to this class so we spent some time practicing zeroing it out, balancing and reading the scale. The project was much messier than I had anticipated. Several students popped their bags (on purpose maybe?), spilled the vinegar and dropped the baking soda between the balance and their bags so we spent a log of time cleaning. The students were so excited to see the bags inflate and feel the change in temperature indicating a chemical reaction had occurred. This helped them strive to find the right combination. There was some disappointment when the eggs broke during the first round of testing, but it helped them focus on making the second design more successful.
Next time I would spend more time making the vehicles look more like cars and conduct different tests besides the drop. We discussed adding wheels to the vehicles and using balloons to project the cars forward to create head-on collisions as another test for the airbags.
Project Timeline
Testing
Redesigning
10 days of 42-minute class periods
Week 1
Day 1 & 2: Take a pretest on engineering design vocabulary and complete a web quest to research how airbags work.
Day 3: Share results and discuss findings as a class.
Day 4 & 5: Create airbags using a multi-step procedure. Conduct multiple trials.
Week 2
Day 6 & 7: Share data from airbag testing and design a vehicle to hold passenger (uncooked egg) with airbags.
Day 8: Test vehicle with passenger and airbags.
Day 9: Redesign vehicle and airbags. Retest.
Day 10: Analyze results, answer questions regarding design and outcome, take posttest.
Analyzing results/sharing data
Results & designs
Acknowledgements
A special thank you to the HFMS 7th Period STEM Class and to ScienceNetLinks.com for the project idea from It’s a Crash Test, Dummy.