Agent Model Story
This model is a simulation of how the Haber process works. The Haber process is a chemical reaction that uses N2 and H2 to produce ammonia (NH3) for industrial use. There is a world with larger, red N2 molecules and smaller, black H2 molecules. There is a catalyst at the top and bottom of the world/container.
Each of the molecules moves randomly around the world and bounces off the vertical walls, and when they touch the top or bottom wall, the molecules are split apart by the catalyst into two separate H or N atoms. The H atoms move across the catalyst until they meet the edge of the container or if they collide with a different atom or molecule. If an H atom collides with an N atom, they form NH. If an H atom collides with an NH molecule, they form NH2. Finally, if an H atom collides with an NH2 molecule, it forms NH3, or ammonia, the desired product. Once the ammonia is formed, it is released from the catalyst and moves randomly around the container, bouncing off the walls.
There are different buttons that change the temperature(speed of the particles), the pressure(volume of the container), and the starting concentration of the reactants (number of particles) for the model, so the differences in the rate and amount of ammonia produced can be observed.
Vensim Model Story
The Vensim model has the reactants and products as different levels and has arrows that connect between them to show how a decrease in the reactant concentration causes a proportional increase in the products (since the reactants are being converted directly into the products). The Vensim model also shows the aspect of the process that it is reversible and must reach an equilibrium. Therefore, the product can also split back into the reactants. The model also graphs the concentrations of the molecules as they change throughout the reaction until they reach equilibrium.
Observations and Reflection
The questions I initially planned for the model to answer were:- How is the rate of the chemical reaction affected by changes in concentration, temperature, pressure/volume, etc?
- How can the reaction rate be maximized so the most product can be created in the fastest time/most efficiently?
- What is the step-by-step process for the reaction to take place?
My hypotheses were that the reaction would be most efficient/the fastest at higher temperatures, higher concentrations, and higher pressures, so as these parameters increased, the rate would become faster. My observations/results from my models seem to support this hypothesis, because in the Vensim model, you can see that the concentrations change more rapidly when temperature and pressure go up, and in the agent model, more ammonia is made more quickly when the parameters are increased.
Some adjustments I had to make to my model to make it more accurate was that I had to make sure that the velocity of the particles was uniform throughout. I also had to change the way that the code checked for collisions since a few of the particles started getting stuck in the wall.
Working on this project taught me a lot about the topic I modeled, and also brushed up some of my chemistry knowledge. I also learned a lot from coding the Javascript for the agent model. For example, I learned about how to create functions with parameters, the importance of keeping track of my variables, and that detailed planning ahead of time is very helpful. Also, when I was working on my Vensim model, I figured out how to get a slider for the levels themselves instead of the variables so that I could adjust the starting concentrations.
Citations
“Commercial Processes.” IMPRESS Education: Catalysis, Commercial Processes, www.spaceflight.esa.int/impress/text/education/Catalysis/Commercial.html.
Libretexts. “The Haber Process.” Chemistry LibreTexts, Libretexts, 19 May 2020, chem.libretexts.org/Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Supplemental_Modules_(Physical_and_Theoretical_Chemistry)/Equilibria/Le_Chatelier's_Principle/The_Haber_Process.
May, Paul. The Haber Process, 1999, www.chm.bris.ac.uk/~paulmay/haber/haber.htm.