There is a lab that is called something like “The Mole Rocket Lab” or “Micro Rockets”. Some of you may be familiar with the lab, but I wanted to write this post to share it with teachers who may not be aware of it.
The Mole Rocket Lab is an excellent opportunity to engage students in collecting data and making decisions about the best mole ratio of gases to use in their rocket. I also want to share how I implement the lab, which may be different than others facilitate it. This lab is one of my favorite activities to do in my classes and I look forward to it every year. The lab is simple, requires limited supplies, students love it (i.e. high engagement level), and I have found it to really set students up for stoichiometry.
Video 1: Mole Rocket Lab, Flinn Scientific YouTube Channel, Bob Becker, 12/19/12. (accessed 5/22/19)
I follow the basic procedure demonstrated in video #1. Other descriptions of the lab can be easily found if you do a web search for “Micro Rocket Lab” or “Mole Rocket Lab”. There is a time investment to build the nozzles for the gas generators and the piezo ignition devices. But, after that initial investment lab set-up is fast and simple in future years.
I have attached the handout I give my students when completing this lab. Before students begin the lab, it is necessary to demonstrate how to set up the gas generators, and to show them how to collect the hydrogen and oxygen gases at the desired ratios. Students think the water displacement technique for measuring and collecting the gas ratios is really cool. My class periods are 75 minutes, and this is plenty of time to demonstrate the procedure, for students to collect the data they need, have time to shoot rockets if they want or get started writing their conclusion.
After students collect their data and start on their conclusion, students will most likely need help when completing the table on the lab handout to determine the left-over reactants. The video referenced above provides a description of how to complete the table (I use the same description, but don’t show students the video). I typically show students how to complete the table for one or two of the mixtures, and leave them to figure out the rest of the table. I instruct students to consider their experimental results together with the expected left-over reactants of each mixture they tested and then write their explanation to the question, “Why are some mixtures of hydrogen and oxygen more explosive than others?” Students may at first feel unsure how to answer the question, but after a brief moment of thought or discussion within their group are usually able to come up with an explanation with little or no further guidance. Students’ explanations are required to be supported with an argument that includes, at minimum, the bullet list of items in the lab handout.
In the past, I have had students make whiteboards and share their results and thoughts with each other before writing their own individual conclusions. However, most student groups tend to reach similar conclusions without too much variability, which isn’t conducive to rich discussion. Therefore, I haven’t found it to be worth the class time to have students share their results and discuss with each other before they write their own individual conclusions for this lab. It is definitely worthwhile to have students write their own individual conclusions while consulting with their group members.
For me, this lab is a keeper because it provides a strong connection of a mole ratio to a real reaction and also provides a brilliant introduction to the concepts of mole ratios and limiting reactants, setting students up really well for the stoichiometry unit.
