A Great Introduction to Stoichiometry

disposable pipet rocket on a piezo lighter

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.

Supporting Information: 

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.

Summary:

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.

Assessment Boundary:
Clarification:

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.

Summary:

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.

Assessment Boundary:
Clarification:

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.

Summary:

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.

Assessment Boundary:
Clarification:

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.

Summary:

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.

Assessment Boundary:
Clarification:

Mathematical and computational thinking at the 9–12 level builds on K–8 and progresses to using algebraic thinking and analysis, a range of linear and nonlinear functions including trigonometric functions, exponentials and logarithms, and computational tools for statistical analysis to analyze, represent, and model data. Simple computational simulations are created and used based on mathematical models of basic assumptions. Use mathematical representations of phenomena to support claims.

Summary:

Mathematical and computational thinking at the 9–12 level builds on K–8 and progresses to using algebraic thinking and analysis, a range of linear and nonlinear functions including trigonometric functions, exponentials and logarithms, and computational tools for statistical analysis to analyze, represent, and model data. Simple computational simulations are created and used based on mathematical models of basic assumptions. Use mathematical representations of phenomena to support claims.

Assessment Boundary:
Clarification: