In the “Airbag challenge” the students are tasked with developing a safe airbag for a car company. This formative assessment explores students’ thinking about the question “How can chemical changes be controlled?” The central concept in this challenge is the application is stoichiometry. Students are expected to use the numbers of moles of reactant consumed or product formed in a balanced chemical equation and to determine the change in the number of moles of any other reactant and product. Students need to use molar mass to convert mass of a reactant or product to moles for use in stoichiometric calculations or to convert moles from stoichiometric calculations to mass. Students use the ideal gas law equation to determine the numbers of moles in a sample of gas not at standard conditions.
In this formative assessment the students were shown three different trials conducted by the teacher with different amounts of the reactants, baking soda and vinegar, to make observations about. Students were then shown videos explaining how an airbag works in an actual car. The students were then tasked with developing the best airbag by first considering the most important factors, safety, and developing a detailed procedure using the 
airbag challenge handout. After completing their experimentation the students were asked to discuss what was successful about their design, what obstacles they encountered, and what recommendations they would make to a company about making a safe airbag. The formative assessment is designed for 10 grade Honors chemistry students. It was implemented at a small suburban school. There are about 700 students total, primarily white with 19 % minority. Graduation rate is more than 95% and the overall school is ranked at the top 5% of all schools in Massachusetts for overall test scores in math and reading proficiency. The student:teacher ratio is 11:1.
Teacher reflections
This challenge gives an opportunity for students to connect real-life chemistry to the classroom. I wanted the topic to be motivating for the students and also something that they were familiar with, so their answers could be revealing about their chemical thinking. I thought that the airbag challenge worked well because most of the students were able to successfully complete the investigation and were able to explain to each other how they designed their experiment. The challenge was accessible and allowed students to think about chemical control. Students were interested in the topic and I had 100 % participation. Students had fun doing the investigation at home and posting the videos about their experimental designs. This challenge required that students used many of the topics we had covered in chemistry, including lab safety, consumer safety and lab techniques, balancing equations, using BCA tables in stoichiometry, calculating moles, using molar ratios, gas laws and experimental design. Overall, I was pleased with the students’ engagement and I was able to identify some areas that students still needed practice on.
Remote learning
One challenge about implementing this FA was that the experimental design was completed at home and students had to use household materials. I had to rely on the students to use what they had available at home, because I did not have a way to send materials to each student. Some students did not have the same white distilled vinegar at home. Some students had bags that were too big and required too much of reactants to be used. Students did not have the correct measuring equipment and they had to improvise using tables, teaspoons or measuring cups to complete the investigation. I had used our live ZOOM session to introduce the activity. To help students with their task I had collected data from three different trials using the given materials. I used cabbage juice to monitor what was going on during the reaction. As a lesson starter, I took images of the three bags and asked students to look at the pictures and write what they noticed was happening in each trial and why. I used the Nearpod platform to post questions and create meaningful interactions with the students. The Nearpod platform is a great tool that allows cooperative learning. It can be used live with a teacher leading the lesson and controlling the slides or with students working through the lesson individually. The teacher can create an account and send the students a code to join. The teacher can set up the questions to monitor the students’ engagement. Since all students log into Nearpod with their name, the teacher is able to monitor their work throughout the lesson. Students press “Submit” when they are ready to share their work and it appears on the teacher's screen. The teacher may click on a student’s answer and show it to other students, and share. The answer is projected to all other students’ devices. At the end of the lesson the teacher may save the student's work and use the same lesson again. The teacher also may get access to the student’s work. The problem is that the teacher and students need to use either a split ZOOM screen during the live lesson, or two different computers to go from breakout rooms to monitoring students’ responses. I had to use two computers because the PC laptop did not have an option for a split screen. If teachers want to use this option, they need to change the settings on Zoom and check first if the split screen works on their computer. Teachers also need to send students an email about the code, or put the assignment on Google classroom in advance. The other technology I used is Flipgrid. This is a tool that allows students and teachers to create questions, responses and videos about a specific topic. The teacher creates the topic and invites students to access the lesson. The students involved with the challenge created their own videos about the experiment, explaining how they came up with the experimental design and the quantities necessary for the reaction. Both tools are free and easy to use on the computer or phone. I also used Google classroom to collect students’ work that was done the second day in addition to their Flipgrid videos.
Example student work
Summaries of students’ observations during the demonstration
|
TRIAL 1
|
TRIAL 2
|
TRIAL 3
|
Day 1
|
1. Before starting the investigation, please use a few minutes to brainstorm all of the things that you will have to think about to inflate the bag with the maximum firmness using the household materials. |
2. What do you think is the most important to try to figure out first? Why is it important? |
3. What other factors you may need to consider to design your experiment? Why are they important? |
|
| Student 1 |
● What proportions of baking soda to vinegar will create the maximum reaction without wasting too much of each product? Is this experiment more about the mass of each product or about creating the right proportions of each product? ● How big is the bag? ● What are some ways that I can ensure this experiment will not create a huge mess? Where in my house should I complete this experiment so as not to get in the way of anyone? ● Are there any safety precautions I should take before completing this experiment? ● The volume of the bag. ● The amount of CO2 produced in the experiment. |
I think the first thing I should think about is the size of the bag. This is important because it will tell me how much gas the bag will be able to fit without exploding. |
Other important factors are the temperature of the room, the air pressure on the day of testing, the moles of CO2 I will be producing, and the balanced equation with moles of each product and reactant. All of this information is important as it will help me figure out how much of each reactant, in grams, I will need for the experiment, as well as the theoretical mass of the CO2. |
| Student 2 |
● The volume of the bag you are going to use so that you can determine how much gas is needed to fill it. ● Amount of vinegar used in the experiment. ● Amount of baking soda used in the experiment. ● How are you going to calculate moles of CO2 gas. Find the equation to calculate moles of gas (formula). ● Balanced equation of materials/chemicals. ● The timing and how long the reaction takes place. |
First you should try to figure out the volume of the bag you are going to use so that you can determine how much gas is needed to be produced from the reaction to fill the bag. The volume of the bag is important because it tells you how much CO2 must be released during the reaction, which tells you how much baking soda and vinegar you must use in the reaction.
|
● Other factors are temperature. ● Formulas weight and volume and mass. ● These affect the environment of the reaction
|
| Student 3 |
The things you have to think about are amount of substances in reaction, time of reaction, temp. in which the reaction takes place and size of the bag used in reaction, volume, CO2 and formula weight and balance equation. |
The first thing we need to figure out is how much CO2 needs to be produced. This is important because it’ll determine the measurement/amount of baking soda and vinegar needed for the experiment. This also requires you to find the volume of the bag first as well the help find amount of CO2 gas to be produced and the amount of moles. |
Other factors you need to consider are temperature, volume and formula weight/mass. There are important because they are necessary for the based of the reaction. |
|
4. What safety should be considered when designing the airbag? |
5. What do you plan to try to inflate the bag to its firmness? Write your experimental procedure in detail giving the quantities and how you will be placing it in the bag. Show any calculations that may support your thinking for choosing the specific quantities. |
||
| Student 1 |
I should be considering the fact that if I make the explosion too big, the plastic bag might explode. I certainly do not want this to happen, as I would hate to get the vinegar and baking soda mixture in my, or any of my family’s (including my dogs) eyes. I would also hate for this experiment to land on someone’s skin, causing irritation. Also, my dogs have really screwed up digestive systems, and so if this experiment explodes and they lick the mixture somehow, I would have a real medical emergency on my hands. |
1. Calculate the volume of the plastic bag by filling it with water, and measuring the volume of that water in a measuring cup. a. 875 ml / 1000 = 0.875 L 2. Find the temperature of the room where the experiment will be completed, and convert to Kalvin. Also take the air pressure in standard units. a. (67 degrees F - 32) x 5/9 +273 = 292.4 K b. 30.21 inHg/ 30 = 1.01 atm 3. Calculate the moles of CO2 by rearranging the ideal gas law. a. 0.875 L of CO2 needed. b. pv = nRt -> n = pv/Rt c. n = (1atm) (0.875L) / (0.0821)(292.4 K) d. n = 0.0364 mol CO2 4. Write the balanced equation of the experiment and determine amount of moles of reactants needed. a. 1 NaHCO3 + 1 CH3COOH ->1 NaCH3COO + 1 H2O + 1 CO2 i. all mole ratios are 1:1 1. 0.0364 moles of Baking soda (NaHCO3) needed 2. 0.0364 moles of 5 % vinegar (CH3COOH) needed 5. Using the moles of the reactants, calculate the amount of grams of baking soda and vinegar needed for this experiment. a. 0.0364 mol NaHCO3 x 84.01 g/mol = 3.06 g NaHCO3 b. 0.0364 mol CH3COOH x 60.052 g/mol = 2.19 g CH3COOH i. 2.19g CH3OOH x 100g vinegar/5g CH3OOH = 43.8 g 6. Convert grams of reactants to teaspoons. (1 teaspoon = 4.2 g) a. Baking soda: 3.06 g NaHCO3/ 4.2 g = 0.73 teaspoons NcHCO3 b. Vinegar: 43.8 g vinegar/ 4.2 g = 10.4 teaspoons c. 10.4 teaspoons of vinegar / 3 = roughly 3.5 tablespoons of vinegar 7. Lay out a plastic tablecloth on the chosen workspace. 8. Turn the plastic bag on one side and add 0.73 teaspoons of baking soda. 9. Turn the plastic bag on the other side and add 10.4 teaspoons of 5%vinegar. 10. Quickly close the bag and shake until CO2 gas begins to fill up the bag. 11. Record data and observations, take a picture of the bag, and clean up the workspace by emptying the contents of the bag in the sink. |
|
| Student 2 |
● Make sure to have accurate calculations and amount of reactants used in experiment so it does not blow up in face. |
||
| Student 3 |
Make sure accurate amounts of reactants are used, ensure operating in safe temperature, the timing of the reaction is key in its ability to be safety precaution and volume size of bag are fitted for the product of the reaction. |
Baking soda – 3 teaspoons or 12.6 grams Vinegar – 50 mL = 50 grams Volume of bag: 185.92 mL The estimated ratio of baking soda to vinegar is a 1:4 ratio. After doing testing, I concluded that ratio was indeed correct. Trial 2 was the most successful as predicted. |
Day 2
|
1. Before starting the investigation, please use a few minutes to brainstorm all of the things that you will have to think about to inflate the bag with the maximum firmness using the household materials. |
2. What do you think is the most important to try to figure out first? Why is it important? |
3. What other factors you may need to consider to design your experiment? Why are they important? |
|
| Student 1 |
Overall, my estimations of the correct amount of reactants to use was very successful. Using about ¾ of a teaspoon of baking soda (NaHCO3), and 3 ½ tablespoons of vinegar, I was able to create a reaction that produced enough CO2 to completely fill my bag without exploding it. Over all, the bag rose to about 2.5 inches high, and got to be really firm from the air inside of it. I learned that the bag, in order to be filled with 0.875 L of CO2, needed ¾ teaspoon of baking soda to react with 3 ½ tablespoons of vinegar, which would not only create about 0.875 L of CO2, but it would also create H2O and NaCH3COO. |
I encountered many obstacles when performing this experiment. The first obstacle was figuring out the calculations. In order to do this, I really needed to think about using the ideal gas law to find the right amount of CO2 that would be needed, and using that information and the balanced chemical equation to estimate the amounts of vinegar and baking soda needed to produce that much CO2, and then convert them into teaspoons and tablespoons. I also had to re-do my experiment. This is because the first time I tested the reaction, I was unable to close the bag immediately. Thus, the bag lost too much CO2. Clearly, I needed to change my methods, and so I learned that what didn’t work was trying to do this experiment without practicing my methods. So, I practiced closing the bag a couple of times before retrying, as I didn’t want to waste any baking soda or vinegar. The second time I completed this experiment, it worked! |
● How to measure the volume of the bag. ● How to use the volume of the bag to and the ideal gas law to tell me how much CO2 was needed. ● How to use the balanced equation of the vinegar and baking soda reaction to figure out how much vinegar and baking soda I needed. ● How to correctly convert those measurements of vinegar and baking soda into teaspoons and tablespoons. ● How to close the bag fast enough so that no gas escaped. |
| Student 2 |
● My design inflated almost immediately upon adding the vinegar and filled the bag perfectly to make the bag as firm as possible. ● I learned that inflating bag takes precise and accurate measurements along with multiple trials |
● Obstacles that I encountered were finding the exact volume of the bag using water and making sure I had accurate calculations. ● I learned that some of my trials did not work or inflate the air bag to maximum capacity because the ratio of baking soda to vinegar was not correctly proportioned. |
● Volume of plastic bag (airbag) ● Moles of CO2 to fill bag ● Safe temperatures ● Operating correct calculations ● Formulas weight and volume mass ● Size of bag ● Timing/length to inflate bag ● Temperature and pressure of environment ● Amount of materials used |
| Student 3 |
What was successful was that my hypothesis of what amount would work was correct after testing different trials. It takes a specific reaction to inflate and it can’t be more or less. |
Obstacles I encountered were finding the accurate ratio of the baking soda to vinegar and determine the temperature and how it could affect it. Both of these elements, if done wrong will cause the bag to over inflate or under inflate. |
● Amount of baking soda ● Amount of vinegar ● Volume of bag ● Temperature ● Moles/mass and formula weight |
|
4. Now that you had finished the challenge and made the bag with the best firmness, what did you determine was important to consider to inflate the bag? Why was it important? |
5. Now that you completed the challenge, make recommendations about the best and safest way to make the airbags. |
||
| Student 1 |
I believe the most important thing to consider in order to inflate the bag, was the volume of the bag itself. With this information, which as I measured came out to be 0.875 L, allowed me to determine how much CO2 I needed to fill the bag, which allowed me to complete all of my other calculations. Ultimately, knowing the volume of the bag was important because it allowed me to calculate exactly how much baking soda and vinegar I needed, and so I was able to complete this experiment quickly, without mess, and while also using as little materials as possible. |
● It is really important to know the volume of the airbag that is going to be used. Without this information, it will be impossible to calculate exactly how many chemicals you will need in order to fill the bag to maximum capacity. ● It is vital, as well, that proper measurements of temperature and air pressure are taken when using the ideal gas law to calculate how many moles of gas are needed to fill the air bag. Without this information, the rest of your calculations will be incorrect. ● It is also really important that you do your calculations before you test. You should not go into this experiment without knowing exactly how much of each chemical you will need in order to fill the air bag with enough gas. You really have to work backwards in this experiment. ● It is also really important to make sure that there is no way for extra gas to escape while completing your air bag experiment. This way, your test will be an accurate representation of the reaction between the chemicals you use, and will tell you how much of your chemicals you need. |
|
| Student 2 |
● The atmosphere temperature and pressure were important to the experiment because they impact the environment. ● The volume of the bag was important because it helped to find the moles of CO2 needed to inflate the bag which helped determine the amount of baking soda and vinegar needed for maximum firmness and safety precautions. |
● Make sure to have precise and accurate calculations. ● Compare many test trials to ensure maximum firmness is being used in cars for safety. ● Consider all possible circumstances. |
|
| Student 3 |
I determined that all aspects necessary to inflate the bag are important. Mainly the volume of the bag because that is what determines the amount of moles of baking soda and vinegar are needed. |
● Experiment in many trials ● Do calculations first so they aren’t just making random guesses ● Consider all circumstances of the reactions. |
NGSS
Analyzing data in 9–12 builds on K–8 and progresses to introducing more detailed statistical analysis, the comparison of data sets for consistency, and the use of models to generate and analyze data.
Analyzing data in 9–12 builds on K–8 and progresses to introducing more detailed statistical analysis, the comparison of data sets for consistency, and the use of models to generate and analyze data. Analyze data using tools, technologies, and/or models (e.g., computational, mathematical) in order to make valid and reliable scientific claims or determine an optimal design solution.
Constructing explanations and designing solutions in 9–12 builds on K–8 experiences and progresses to explanations and designs that are supported by multiple and independent student-generated sources of evidence consistent with scientific ideas, principles, and theories.
Constructing explanations and designing solutions in 9–12 builds on K–8 experiences and progresses to explanations and designs that are supported by multiple and independent student-generated sources of evidence consistent with scientific ideas, principles, and theories. Construct and revise an explanation based on valid and reliable evidence obtained from a variety of sources (including students’ own investigations, models, theories, simulations, peer review) and the assumption that theories and laws that describe the natural world operate today as they did in the past and will continue to do so in the future.
Engaging in argument from evidence in 9–12 builds on K–8 experiences and progresses to using appropriate and sufficient evidence and scientific reasoning to defend and critique claims and explanations about natural and designed worlds. Arguments may also come from current scientific or historical episodes in science.
Engaging in argument from evidence in 9–12 builds on K–8 experiences and progresses to using appropriate and sufficient evidence and scientific reasoning to defend and critique claims and explanations about natural and designed worlds. Arguments may also come from current scientific or historical episodes in science.
Evaluate the claims, evidence, and reasoning behind currently accepted explanations or solutions to determine the merits of arguments.
Planning and carrying out investigations in 9-12 builds on K-8 experiences and progresses to include investigations that provide evidence for and test conceptual, mathematical, physical, and empirical models.
Planning and carrying out investigations in 9-12 builds on K-8 experiences and progresses to include investigations that provide evidence for and test conceptual, mathematical, physical, and empirical models. Plan and conduct an investigation individually and collaboratively to produce data to serve as the basis for evidence, and in the design: decide on types, how much, and accuracy of data needed to produce reliable measurements and consider limitations on the precision of the data (e.g., number of trials, cost, risk, time), and refine the design accordingly.