Lego Equation Balancer


Use Lego and a Laser Cutter to create a system of gears that help students solve and visualize chemical balancing equations. 

The teacher's challenge to the student: Build a physical machine that helps explain or visualize a common problem in chemistry. 

By Trang Ngo & Will Luna, Tufts University CEEO 2015

The Finished Project
Building the Final Project

 This video outlines building the gears system out of legos, setting up and solving the problem using wood tiles, and then applying that solution to the gear system. Instructions on using the laser cutter to create the tiles can be found below. Keep in mind that laser cutting is not necessary for this project - the tiles could be made out of paper. 

The Big Idea
We gave ourselves the prompt:
  Create a physical model that represents balancing chemical equations. 
 The report outlines how we went from brainstorming and testing a wide variety of ideas to design (without considering material constraints) to our final project (considering material constraints). 

 You could totally build Rome in a day. It's the architects that are going to hold you up. 
- Julius Caesar

Below, we describe the steps we took, as students following the engineering design process, to reach our end product. That process (once again):
Ask, Brainstorm, Plan, Create, Improve

Notice how 'Create' is the fourth step? While there is a tendency to focus on the building stage of the process, as a teacher it is important to keep in mind that the students will spend the majority of their time on developing their ideas, not making them. 

Ask <---> Brainstorm

As a teacher, the first part of this exercise is the most difficult to conceptualize: come up with a theoretical prompt that you could assign your students, and then try and complete the assignment to determine if the prompt has value. 

Our first three prompts did not yield satisfying projects, so we determined that only the fourth (create a physical representation of the chemical balancing process) would be fitting to assign high-school students. 

Putting time into an idea and then leaving it may be a big hurdle for students and teachers alike, but it is an essential part of the design thinking process.

VSEPR Construction Idea
Covalence & Ionic Bonding Idea

Idea: Students must create a physical game that allows them to practice and review chemical bonding.  

Objective: Give students hands-on experience creating chemical bonds in an interesting, non-traditional way. 

Brainstorm: We considered 3D-Printing valence shells with the respective number of slots (for electrons) for the first three orbitals around the nucleus. Electrons could be inserted, removed, and conjoined between the valence shells to represene Ionic and Covalent Bonding. 

Problems: It is difficult to create a meaningful physical model of Chemical Bonding without access to a 3D-Printer, and our design felt too sloppy. 

Slow-Motion Video Idea

Idea: The students can choose a chemical process to film in time-lapse or slow-motion. Through the video footage achieved, they need to explain the chemical concept behind this process.
Chemical processes which occur over long intervals of time, such as the three states of water or the diffusion of liquid, can be recorded through time-lapse. 

Chemical processes which occur over extremely short periods of time, such as the Tie Dye Milk experiment, can be filmed in slow-motion. 

Objective: By recording such chemical processes and observing the footage, students can gain better understanding of the related chemical concepts. In this project, they can also learn to explain chemical concepts through concrete observation. 

Equation Balancer Idea

 Idea: Students must create a physical model that represents and/or teaches the concept of balancing chemical equations. 

Objective: Allow students to review a concept in chemistry (balancing equations) through analytical and design thinking skills. 

Products: See below (since this is the project we went with), a system of gears and wooden tiles that represent the relationships between the coefficients of a given equation. 

Problems: See below. The interval markings beneath the gears are imprecise - using differently sized gears would have made a better final project. 

The Gear System
The Planning Process

We tried to figure out a method to show the coefficients in accordance with the stoichiometric relationships between the products and reactants. 

At first, a peg was inserted into one hole on each gear to track the gear's movement while being rotated. However, the numerical values of different coefficients cannot be determined in this case. In the end, we decided to position the balancer on a piece of paper and mark different intervals. 

Experimenting with smaller gears

Smaller gears were used to illustrate the different rates of changes in a chemical equation. In other words, smaller gears can represent a component with higher coefficient, turning faster than larger gears. However, because only 40-teeth and 24-teeth gears were available, we could not use them to accurately represent different coefficients in an equation. 

Creating the Equation Tiles
The Finished Tiles
While we used a laser cutter, these tiles could be created using only pencil and paper!
Lego Gear
Improve (Additional Suggestions)
  • The gears can be chosen among cogwheels of varying sizes- with 48, 24, and 12 teeth- to represent the stoichiometric relationship between different components in an equation.
  •  The gears can be color-coded to differentiate between reactants and products. 
  • Students can experiment with more complex equations by adding or changing the configuration of the gears in this lego balancer. 

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